Showing 1–31 of 31 results for author: Meyer, E

Mechanical detection of sub-band mobilities of two-dimensional electron gas on reduced SrTiO$_3$(001) surface

Authors: Akash Gupta, Marcin Kisiel, Remy Pawlak, Ernst Meyer

Abstract: The two-dimensional electron gas (2DEG) in reduced strontium titanate offers a versatile platform for oxide electronics, yet its dissipation mechanisms under field driven charge fluctuations remain poorly understood. Here, we combine low-temperature atomic force microscopy with scanning tunnelling spectroscopy to probe the force and dissipation responses of a mechanical oscillator interacting with… ▽ More The two-dimensional electron gas (2DEG) in reduced strontium titanate offers a versatile platform for oxide electronics, yet its dissipation mechanisms under field driven charge fluctuations remain poorly understood. Here, we combine low-temperature atomic force microscopy with scanning tunnelling spectroscopy to probe the force and dissipation responses of a mechanical oscillator interacting with the STO 2DEG. The observation of Rydberg like image potential states by tunnelling experiments confirm the 2DEG formation, while dissipation spectroscopy reveals bias-dependent peaks linked to local electrostatic gating and charge redistribution within the 2DEG energy sub-bands. These features are quantitatively explained by variations in quantum capacitance as carrier density is tuned by electric fields. Under magnetic fields, dissipation peaks obey the Kohler's rule, allowing extraction of carrier mobilities in each sub-band. Our results establish a non-invasive AFM - based methodology for quantifying energy losses in quantum oxides, providing new insights into charge dynamics relevant for spintronic applications. △ Less

Submitted 12 May, 2026; originally announced May 2026.

Comments: 30 pages, 4 figures

Shining light on short-range atomic ordering in semiconductors alloys

Authors: Anis Attiaoui, Shunda Chen, Joseph C. Woicik, J. Zach Lentz, Liliane M. Vogl, Jarod E. Meyer, Kunal Mukherjee, Andrew Minor, Tianshu Li, Paul C. McIntyre

Abstract: The functional properties of semiconductors are typically controlled by tailoring their chemical composition and their state of strain, and by controlling their long-range structural order, including the presence of extended defects such as dislocations. In addition to these approaches, theoretical predictions suggest that short-range order (SRO) of atoms in group-IV semiconductor alloys can modif… ▽ More The functional properties of semiconductors are typically controlled by tailoring their chemical composition and their state of strain, and by controlling their long-range structural order, including the presence of extended defects such as dislocations. In addition to these approaches, theoretical predictions suggest that short-range order (SRO) of atoms in group-IV semiconductor alloys can modify the bandgap, a defining property of any semiconductor. Herein, a new machine learning enabled, computation-guided methodology for extended X-ray absorption fine structure (EXAFS) analysis of SRO is used to quantify the effects of local atomic order on the bandgap of germanium-tin (GeSn) alloy single crystal nanostructures with well-controlled strain and composition. Correlative analysis of EXAFS and photoluminescence (PL) establishes the relationship between bandgap and the Warren-Cowley short-range order (WC-SRO) parameter of the GeSn alloys. It is further demonstrated that SRO can be tuned over a broad range by post-deposition annealing of the alloy crystals. This work establishes control of SRO as an important design parameter for semiconducting properties and suggests the potential for quantitative measurement and tuning of SRO in other semiconductor alloy systems. △ Less

Submitted 7 April, 2026; v1 submitted 29 March, 2026; originally announced March 2026.

Comments: 10 pages in the main draft, with 4 pages in Methods section. 4 Figures in total

Mid-infrared LEDs based on lattice-mismatched hybrid IV-VI/III-V heterojunctions

Authors: Jarod E. Meyer, Biridiana Rodriguez, Leland Nordin, Kunal Mukherjee

Abstract: Light-emitting diodes (LEDs) can bridge the gap between narrow linewidth, expensive lasers and broadband, inefficient thermal globars for low-cost chemical sensing in the mid-infrared (mid-IR). However, the efficiency of III-V based mid-IR LEDs at room temperature is low, primarily limited by strong nonradiative Auger-Meitner recombination that is only partially overcome with complex quantum-engin… ▽ More Light-emitting diodes (LEDs) can bridge the gap between narrow linewidth, expensive lasers and broadband, inefficient thermal globars for low-cost chemical sensing in the mid-infrared (mid-IR). However, the efficiency of III-V based mid-IR LEDs at room temperature is low, primarily limited by strong nonradiative Auger-Meitner recombination that is only partially overcome with complex quantum-engineered active regions. Here, we exploit the intrinsically low Auger Meitner recombination rates of the IV-VI semiconductors PbSe and PbSnSe, while leveraging the mature III-V platform through the fabrication of hybrid heterojunctions that mediate the ~8% lattice mismatch to GaAs. Electrically injected n-PbSe/p-GaAs LEDs emit at 3.8 um with output powers up to 400 uW under pulsed operation and a peak wall plug efficiency of 0.08% at room temperature, approaching the performance of commercial III-V LEDs at similar wavelengths. Incorporating 7% Sn extends the emission to 5 um in GeSe/PbSnSe/GaAs LEDs with output powers up to 45 uW. Notably, both devices operate despite threading dislocation densities on the order of 1e9/cm^2, underscoring the potential of hybrid IV-VI/III-V heterojunction architectures. We show that combining the complementary advantages of IV-VI and III-V semiconductors offers a simple and efficient mid IR optoelectronic platform for a rapidly expanding set of applications. △ Less

Submitted 27 January, 2026; v1 submitted 13 August, 2025; originally announced August 2025.

Comments: 25 pages, 4 figures

Negative differential conductance in triangular molecular assemblies

Authors: Chao Li, Vladislav Pokorný, Prokop Hapala, Martin Žonda, Ping Zhou, Silvio Decurtins, Shi-Xia Liu, Fengqi Song, Rémy Pawlak, Ernst Meyer

Abstract: We report the creation and characterization of a molecular-scale negative differential conductance (NDC) device by assembling a triangular trimer of 4,5,9,10-tetrabromo-1,3,6,8-tetraazapyrene (TBTAP) molecules on a superconducting Pb(111) substrate. Using low-temperature scanning tunneling spectroscopy, we observe robust NDC behavior manifesting as a decrease in current with increasing voltage bet… ▽ More We report the creation and characterization of a molecular-scale negative differential conductance (NDC) device by assembling a triangular trimer of 4,5,9,10-tetrabromo-1,3,6,8-tetraazapyrene (TBTAP) molecules on a superconducting Pb(111) substrate. Using low-temperature scanning tunneling spectroscopy, we observe robust NDC behavior manifesting as a decrease in current with increasing voltage between 0.7-0.9 V arising from the interplay of Coulomb blockade and strong inter-molecular capacitive coupling within the molecular cluster. Gate-controlled charging and discharging processes are directly visualized via two-dimensional differential conductance mapping, which reveals the emergence of Coulomb rings and spatial regions of NDC. Theoretical modeling using a three-impurity Anderson model and master equation approach quantitatively reproduces the experimental observations and demonstrates that the NDC emerges purely from electron correlations, independent of the underlying superconductivity. By tuning the geometry to a hexamer structure, we further show that cluster topology provides versatile control over electronic properties at the molecular scale. These results establish a functional platform for implementing multifunctional molecular devices and highlight a strategy toward programmable and scalable nanoelectronics. △ Less

Submitted 7 August, 2025; originally announced August 2025.

Superlubricity of Borophene: Tribological Properties in Comparison to hBN

Authors: Antoine Hinaut, B. Sena Tömekçe, Shuyu Huang, Yiming Song, Ernst Meyer, Antonio Cammarata, Willi Auwärter, Thilo Glatzel

Abstract: The tribological performance of 2D materials makes them good candidates toward a reduction of friction at the macroscale. Superlubricity has been observed for graphene, MoS\textsubscript{2} and MXenes and hexagonal boron nitride (hBN) is used to reduce or tune friction, but other materials are investigated as potential candidates for low-lubricity applications. Specifically, borophene is predicted… ▽ More The tribological performance of 2D materials makes them good candidates toward a reduction of friction at the macroscale. Superlubricity has been observed for graphene, MoS\textsubscript{2} and MXenes and hexagonal boron nitride (hBN) is used to reduce or tune friction, but other materials are investigated as potential candidates for low-lubricity applications. Specifically, borophene is predicted to have ultra-low friction. Here, we experimentally investigate frictional properties of borophene and use a borophene-hBN lateral heterostructure to directly compare the tribological properties of the two complementary 2D materials. In particular, we investigate the friction between a sliding tip and (i) the weakly corrugated $\mathcal{X}_6$-borophene layer on Ir(111) or (ii) the hBN/Ir(111) superlattice structures with a strongly corrugated moiré reconstruction. Our experimental study performed in ultra-high vacuum at room temperature combined with a Prandtl-Tomlinson (PT) model calculation confirms the superlubricity predicted for borophene, while hBN, which exhibits a higher friction, is nevertheless confirmed as a low friction material. Ab initio calculations show that the lower friction of $\mathcal{X}_6$-borophene with respect to hBN can be rationalized by weaker tip/surface interactions. In addition, we assess structural and electrical properties of borophene and hBN by using scanning probe techniques and compare their dissipation under the oscillating tip to investigate the possible path of energy dissipation occurring during friction. Our study demonstrates the low frictional properties of borophene and the potential of lateral heterostructure investigations to directly compare the properties of these 2D materials. △ Less

Submitted 10 July, 2025; originally announced July 2025.

Heteroepitaxial growth of highly anisotropic $Sb_{2}Se_{3}$ films on GaAs

Authors: Kelly Xiao, Virat Tara, Pooja D. Reddy, Jarod E. Meyer, Alec M. Skipper, Rui Chen, Leland J. Nordin, Arka Majumdar, Kunal Mukherjee

Abstract: The epitaxial integration of anisotropic materials with mainstream cubic semiconductors opens new routes to advanced electronic and photonic devices with directional properties. In this work, we synthesize heteroepitaxial thin films of orthorhombic "quasi-1D" $Sb_{2}Se_{3}$ on cubic GaAs(001) using molecular beam epitaxy. Traditionally, the synthesis of anisotropic films with low symmetry material… ▽ More The epitaxial integration of anisotropic materials with mainstream cubic semiconductors opens new routes to advanced electronic and photonic devices with directional properties. In this work, we synthesize heteroepitaxial thin films of orthorhombic "quasi-1D" $Sb_{2}Se_{3}$ on cubic GaAs(001) using molecular beam epitaxy. Traditionally, the synthesis of anisotropic films with low symmetry materials is challenging due to multiple grain orientations that form. On a macroscopic scale, such a film tends towards isotropic properties, even if individual grains possess anisotropic responses. We achieve epitaxial $Sb_{2}Se_{3}$ grains on pristine homoepitaxial GaAs templates at low temperatures of 180-200 °C. With the $Sb_{2}Se_{3}$ 1D axis aligned in-plane to GaAs [110] and the primary van der Waals direction lying out-of-plane, we find a birefringence of 0.2 between in-plane orthogonal directions and a giant out-of-plane birefringence greater than 1 at telecom wavelengths. Growth at higher temperatures up to 265 °C yields $Sb_{2}Se_{3}$ of an unusual in-plane rotated texture that further enhances the in-plane optical index anisotropy to 0.3. △ Less

Submitted 6 February, 2025; originally announced February 2025.

Comments: 18 pages, 4 figures

Journal ref: Mater. Horiz., 2025,12, 5829-5838

Spin Excitations of High Spin Iron(II) in Metal-Organic Chains on Metal and Superconductor

Authors: Jung-Ching Liu, Chao Li, Outhmane Chahib, Xing Wang, Simon Rothenbühler, Robert Häner, Silvio Decurtins, Ulrich Aschauer, Shi-Xia Liu, Ernst Meyer, Rémy Pawlak

Abstract: Many-body interactions in metal-organic frameworks are fundamental for emergent quantum physics. Unlike their solution counterpart, magnetization at surfaces in low-dimensional analogues is strongly influenced by magnetic anisotropy induced by the substrate and still not well understood. Here, we use on-surface coordination chemistry to synthesize on Ag(111) and superconducting Pb(111) an iron-bas… ▽ More Many-body interactions in metal-organic frameworks are fundamental for emergent quantum physics. Unlike their solution counterpart, magnetization at surfaces in low-dimensional analogues is strongly influenced by magnetic anisotropy induced by the substrate and still not well understood. Here, we use on-surface coordination chemistry to synthesize on Ag(111) and superconducting Pb(111) an iron-based spin chain by using pyrene-4,5,9,10-tetraone precursors as ligands. Using low-temperature scanning probe microscopy, we compare their structures and low-energy spin excitations of coordinated Fe atoms with high S = 2 spin-state. Although the chain and coordination centers are identical on both substrates, the long-range spin-spin coupling due to a superexchange through the ligand observed on Ag is absent on Pb(111). We ascribe this reduction of spin-spin interactions on Pb to the depletion of electronic states around the Fermi level in the Pb(111) superconductor as compared to silver. △ Less

Submitted 30 September, 2024; originally announced September 2024.

Nanoscale Control of Quantum States in Radical Molecules on Superconducting Pb(111)

Authors: Chao Li, Vladislav Pokorný, Martin Žonda, Jung-Ching Liu, Ping Zhou, Outhmane Chahib, Thilo Glatzel, Robert Häner, Silvio Decurtins, Shi-Xia Liu, Rémy Pawlak, Ernst Meyer

Abstract: Magnetic impurities on superconductors present a viable platform for building advanced applications in quantum technologies. However, a controlled manipulation of their quantum states continues to pose a significant challenge, hindering the progress in the field. Here we show the manipulation of magnetic states in the radical molecule 4,5,9,10-tetrabromo-1,3,6,8-tetraazapyrene (TBTAP) on a Pb(111)… ▽ More Magnetic impurities on superconductors present a viable platform for building advanced applications in quantum technologies. However, a controlled manipulation of their quantum states continues to pose a significant challenge, hindering the progress in the field. Here we show the manipulation of magnetic states in the radical molecule 4,5,9,10-tetrabromo-1,3,6,8-tetraazapyrene (TBTAP) on a Pb(111) superconducting surface using low-temperature scanning tunneling microscopy. Tunneling spectra reveal Yu-Shiba-Rusinov (YSR) states near the Fermi energy in isolated molecules. A quantum phase transition from singlet to doublet ground state is induced by changing the tip-molecule distance. Additionally, the presence of a second TBTAP molecule allows tuning of the YSR state position by altering the relative distance and can induce splitting of the YSR states for certain orientations. The construction of molecular chains up to pentamers shows periodic arrangements of charged and neutral molecules, with even-numbered chains forming a charged dimer structure at one end. Information can be encoded in these chains by switching the dimer position. These findings elucidate interactions between molecular assemblies and superconducting substrates, paving the way for advanced quantum-state engineering. △ Less

Submitted 9 August, 2024; originally announced August 2024.

Journal ref: ACS Nano 19, 3403 (2025)

Probing charge redistribution at the interface of self-assembled cyclo-P5 pentamers on Ag(111)

Authors: Outhmane Chahib, Yulin Yin, Jung-Ching Liu, Chao Li, Thilo Glatzel, Feng Ding, Qinghong Yuan, Ernst Meyer, Rémy Pawlak

Abstract: Phosphorus pentamer (cyclo-P5-) ions are unstable in nature but can be synthesized at the Ag(111) surface. Unlike monolayer black phosphorous, little is known about their electronic properties when in contact with metal electrodes, although this is crucial for future applications. Here we characterize the atomic structure of cyclo-P5 assembled on Ag(111) using atomic force microscopy with function… ▽ More Phosphorus pentamer (cyclo-P5-) ions are unstable in nature but can be synthesized at the Ag(111) surface. Unlike monolayer black phosphorous, little is known about their electronic properties when in contact with metal electrodes, although this is crucial for future applications. Here we characterize the atomic structure of cyclo-P5 assembled on Ag(111) using atomic force microscopy with functionalized tips and density functional theory. Combining force and tunneling spectroscopy, we find that a strong charge transfer induces an inward dipole moment at the cyclo-P5/Ag interface as well as the formation of an interface state. We probe the image potential states by field-effect resonant tunneling and quantify the increase of the local change of work function of 0.46 eV at the cyclo-P5 assembly. Our results suggest that the high-quality of the cyclo-P5/Ag interface might serve as a prototypical system for electric contacts in phosphorus-based semiconductor devices. △ Less

Submitted 23 January, 2024; originally announced January 2024.

Comments: 25 pages, 4 figures

Gate-tunable topological superconductivity in a supramolecular electron spin lattice

Authors: Rémy Pawlak, Jung-Ching Liu, Chao Li, Richard Hess, Hongyan Chen, Carl Drechsel, Ping Zhou, Robert Häner, Ulrich Aschauer, Thilo Glatzel, Silvio Decurtins, Daniel Loss, Jelena Klinovaja, Shi-Xia Liu, Wulf Wulfhekel, Ernst Meyer

Abstract: Topological superconductivity emerges in chains or arrays of magnetic atoms coupled to a superconductor. However, the external controllability of such systems with gate voltages is detrimental for their future implementation in a topological quantum computer. Here we showcase the supramolecular assembly of radical molecules on Pb(111), whose discharge is controlled by the tip of a scanning tunneli… ▽ More Topological superconductivity emerges in chains or arrays of magnetic atoms coupled to a superconductor. However, the external controllability of such systems with gate voltages is detrimental for their future implementation in a topological quantum computer. Here we showcase the supramolecular assembly of radical molecules on Pb(111), whose discharge is controlled by the tip of a scanning tunneling microscope. Charged molecules carry a spin-1/2 state, as confirmed by observing Yu-Shiba-Rusinov in-gap states by tunneling spectroscopy at millikelvin temperature. Low energy modes are localized at island boundaries with a long decay towards the interior, whose spectral signature is consistent with Majorana zero modes protected by mirror symmetry. Our results open up a vast playground for the synthesis of gate-tunable organic topological superconductors. △ Less

Submitted 22 December, 2023; v1 submitted 27 October, 2023; originally announced October 2023.

Comments: 21 pages 5 figures

Atomically precise incorporation of BN doped rubicene into graphene nanoribbons

Authors: Remy Pawlak, Khalid N. Anindya, Toshiki Shimizu, Jung-Ching Liu, Takumi Sakamaki, Rui Shang, Alain Rochefort, Eiichi Nakamura, Ernst Meyer

Abstract: Substituting heteroatoms and non-benzenoid carbons into nanographene structure offers an unique opportunity for atomic engineering of electronic properties. Here we show the bottom-up synthesis of graphene nanoribbons (GNRs) with embedded fused BN-doped rubicene components on a Au(111) surface using on-surface chemistry. Structural and electronic properties of the BN-GNRs are characterized by scan… ▽ More Substituting heteroatoms and non-benzenoid carbons into nanographene structure offers an unique opportunity for atomic engineering of electronic properties. Here we show the bottom-up synthesis of graphene nanoribbons (GNRs) with embedded fused BN-doped rubicene components on a Au(111) surface using on-surface chemistry. Structural and electronic properties of the BN-GNRs are characterized by scanning tunneling microscopy (STM) and atomic force microscopy (AFM) with CO-terminated tips supported by numerical calculations. The periodic incorporation of BN heteroatoms in the GNR leads to an increase of the electronic band gap as compared to its undoped counterpart. This opens avenues for the rational design of semiconducting GNRs with optoelectronic properties. △ Less

Submitted 13 June, 2023; originally announced June 2023.

Comments: 18 pages, 4 figures

Journal ref: J. Phys. Chem. C 2022, 126, 46, 19726-19732

Polygonal tessellations as predictive models of molecular monolayers

Authors: Krisztina Regős, Rémy Pawlak, Xing Wang, Ernst Meyer, Silvio Decurtins, Gábor Domokos, Kostya S. Novoselov, Shi-Xia Liu, Ulrich Aschauer

Abstract: Molecular self-assembly plays a very important role in various aspects of technology as well as in biological systems. Governed by the covalent, hydrogen or van der Waals interactions - self-assembly of alike molecules results in a large variety of complex patterns even in two dimensions (2D). Prediction of pattern formation for 2D molecular networks is extremely important, though very challenging… ▽ More Molecular self-assembly plays a very important role in various aspects of technology as well as in biological systems. Governed by the covalent, hydrogen or van der Waals interactions - self-assembly of alike molecules results in a large variety of complex patterns even in two dimensions (2D). Prediction of pattern formation for 2D molecular networks is extremely important, though very challenging, and so far, relied on computationally involved approaches such as density functional theory, classical molecular dynamics, Monte Carlo, or machine learning. Such methods, however, do not guarantee that all possible patterns will be considered and often rely on intuition. Here we introduce a much simpler, though rigorous, hierarchical geometric model founded on the mean-field theory of 2D polygonal tessellations to predict extended network patterns based on molecular-level information. Based on graph theory, this approach yields pattern classification and pattern prediction within well-defined ranges. When applied to existing experimental data, our model provides an entirely new view of self-assembled molecular patterns, leading to interesting predictions on admissible patterns and potential additional phases. While developed for hydrogen-bonded systems, an extension to covalently bonded graphene-derived materials or 3D structures such as fullerenes is possible, significantly opening the range of potential future applications. △ Less

Submitted 8 August, 2022; originally announced August 2022.

Energy dissipation from confined states in nanoporous molecular networks

Authors: Philipp D Astolfo, Xing Wang, Xunshan Liu, Marcin Kisiel, Carl Drechsel, Alexis Baratoff, Ulrich Aschauer, Silvio Decurtins, Shi-Xia Liu, Remy Pawlak, Ernst Meyer

Abstract: Crystalline nanoporous molecular networks are assembled on the Ag(111) surface, where the pores confine electrons originating from the surface state of the metal. Depending on the pore sizes and their coupling, an antibonding level is shifted upwards by 0.1 to 0.3 eV as measured by scanning tunneling microscopy. On molecular sites, a down-shifted bonding state is observed, which is occupied under… ▽ More Crystalline nanoporous molecular networks are assembled on the Ag(111) surface, where the pores confine electrons originating from the surface state of the metal. Depending on the pore sizes and their coupling, an antibonding level is shifted upwards by 0.1 to 0.3 eV as measured by scanning tunneling microscopy. On molecular sites, a down-shifted bonding state is observed, which is occupied under equilibrium conditions. Low-temperature force spectroscopy reveals energy dissipation peaks and jumps of frequency shifts at bias voltages, which are related to the confined states. The dissipation maps show delocalization on the supra-molecular assembly and a weak distance-dependence of the dissipation peaks. These observations indicate that two-dimensional arrays of coupled quantum dots are formed, which are quantitatively characterized by their quantum capacitances and resonant tunneling rates. Our work provides a method for studying the capacitive and dissipative response of quantum materials with nanomechanical oscillators. △ Less

Submitted 5 September, 2022; v1 submitted 20 May, 2022; originally announced May 2022.

Comments: 24 pages, 4 figures

Proximity-Induced Superconductivity in Atomically Precise Nanographene

Authors: Jung-Ching Liu, Rémy Pawlak, Xing Wang, Philipp D'Astolfo, Carl Drechsel, Ping Zhou, Silvio Decurtins, Ulrich Aschauer, Shi-Xia Liu, Wulf Wulfhekel, Ernst Meyer

Abstract: Obtaining a robust superconducting state in atomically precise nanographene (NG) structures by proximity to a superconductor could foster the discovery of topological superconductivity in graphene. On-surface synthesis of such NGs has been achieved on noble metals or metal oxides, however, it is still absent on superconductors. Here, we present a synthetic method to induce superconductivity to pol… ▽ More Obtaining a robust superconducting state in atomically precise nanographene (NG) structures by proximity to a superconductor could foster the discovery of topological superconductivity in graphene. On-surface synthesis of such NGs has been achieved on noble metals or metal oxides, however, it is still absent on superconductors. Here, we present a synthetic method to induce superconductivity to polymeric chains and NGs adsorbed on the superconducting Nb(110) substrate covered by thin Ag films. Using atomic force microscopy at low-temperature, we characterize the chemical structure of each sub-product formed on the superconducting Ag layer. Scanning tunneling spectroscopy further allows us to elucidate electronic properties of these nanostructures, which consistently show a superconducting gap. We foresee our approach to become a promising platform for exploring the interplay between carbon magnetism and superconductivity at the fundamental level. △ Less

Submitted 1 February, 2022; originally announced February 2022.

Comments: 17 pages, 4 figures

Band Gap of Atomically Precise Graphene Nanoribbons as a Function of Ribbon Length and Termination

Authors: Leopold Talirz, Hajo Söde, Shigeki Kawai, Pascal Ruffieux, Ernst Meyer, Xinliang Feng, Klaus Müllen, Roman Fasel, Carlo A. Pignedoli, Daniele Passerone

Abstract: We study the band gap of finite $N_A=7$ armchair graphene nanoribbons (7-AGNRs) on Au(111) through scanning tunneling microscopy/spectroscopy combined with density functional theory calculations. The band gap of 7-AGNRs with lengths of 6 nm and more is converged to within 0.1 eV of its bulk value of 2.3 eV, while the band gap opens by several hundred meV in very short 7-AGNRs. The termination has… ▽ More We study the band gap of finite $N_A=7$ armchair graphene nanoribbons (7-AGNRs) on Au(111) through scanning tunneling microscopy/spectroscopy combined with density functional theory calculations. The band gap of 7-AGNRs with lengths of 6 nm and more is converged to within 0.1 eV of its bulk value of 2.3 eV, while the band gap opens by several hundred meV in very short 7-AGNRs. The termination has a significant effect on the band gap, doubly hydrogenated termini yielding a lower band gap than singly hydrogenated ones. △ Less

Submitted 3 October, 2019; originally announced October 2019.

Comments: Submitted version (preprint, pre-reviewing) to ChemPhysChem (An invited contribution to a Special issue on On-SurfaceSynthesis)

Journal ref: Published in Chem Phys Chem 2019, 20, 2348-2353

Majorana Fermions in Magnetic Chains

Authors: Rémy Pawlak, Silas Hoffman, Jelena Klinovaja, Daniel Loss, Ernst Meyer

Abstract: Majorana fermions have recently garnered a great attention outside the field of particle physics, in condensed matter physics. In contrast to their particle physics counterparts, Majorana fermions are zero energy, chargeless, spinless, composite quasiparticles, residing at the boundaries of so-called topological superconductors. Furthermore, in opposition to any particles in the standard model, Ma… ▽ More Majorana fermions have recently garnered a great attention outside the field of particle physics, in condensed matter physics. In contrast to their particle physics counterparts, Majorana fermions are zero energy, chargeless, spinless, composite quasiparticles, residing at the boundaries of so-called topological superconductors. Furthermore, in opposition to any particles in the standard model, Majorana fermions in solid-state systems obey non-Abelian exchange statistics that make them attractive candidates for decoherence-free implementations of quantum computers. In this review, we report on the recent advances to realize synthetic topological superconductors supporting Majorana fermions with an emphasis on chains of magnetic impurities on the surface of superconductors. After outlining the theoretical underpinning responsible for the formation of Majorana fermions, we report on the subsequent experimental efforts to build topological superconductors and the resulting evidence in favor of Majorana fermions, focusing on scanning tunneling microscopy and the hunt for zero-bias peaks in the measured current. We conclude by summarizing the open questions in the field and propose possible experimental measurements to answer them. △ Less

Submitted 24 September, 2019; originally announced September 2019.

Journal ref: Progress in Particle and Nuclear Physics 107, 1-19 (2019)

Joule meets van der Waals: Mechanical dissipation via image potential states on a topological insulator surface

Authors: Dilek Yildiz, Marcin Kisiel, Urs Gysin, Oguzhan Gürlü, Ernst Meyer

Abstract: Dissipation mechanisms are experimentally studied on topological insulator surfaces of Bi2Te3, where common Joule dissipation was observed to be suppressed due to topologically protected surface states. Thus, a novel type of dissipation mechanism is observed by pendulum AFM, which is related to single electron tunneling resonances into image potential states that are slightly above the Bi2Te3 surf… ▽ More Dissipation mechanisms are experimentally studied on topological insulator surfaces of Bi2Te3, where common Joule dissipation was observed to be suppressed due to topologically protected surface states. Thus, a novel type of dissipation mechanism is observed by pendulum AFM, which is related to single electron tunneling resonances into image potential states that are slightly above the Bi2Te3 surface. The application of a magnetic field leads to the break down of the topological protection of the surface states and restores the expected Joule dissipation process. Nanomechanical energy dissipation experienced by the cantilever of pendulum AFM provides a novel source of information on the dissipative nature of the quantum-tunneling phenomena on the topological insulator surface. △ Less

Submitted 19 July, 2019; originally announced July 2019.

Journal ref: Nature Materials 18, 1201-1206 (2019)

Characterization of Hydrogen Plasma Defined Graphene Edges

Authors: Mirko K. Rehmann, Yemliha B. Kalyoncu, Marcin Kisiel, Nikola Pascher, Franz J. Giessibl, Fabian Muller, Kenji Watanabe, Takashi Taniguchi, Ernst Meyer, Ming-Hao Liu, Dominik M. Zumbuhl

Abstract: We investigate the quality of hydrogen plasma defined graphene edges by Raman spectroscopy, atomic resolution AFM and low temperature electronic transport measurements. The exposure of graphite samples to a remote hydrogen plasma leads to the formation of hexagonal shaped etch pits, reflecting the anisotropy of the etch. Atomic resolution AFM reveals that the sides of these hexagons are oriented a… ▽ More We investigate the quality of hydrogen plasma defined graphene edges by Raman spectroscopy, atomic resolution AFM and low temperature electronic transport measurements. The exposure of graphite samples to a remote hydrogen plasma leads to the formation of hexagonal shaped etch pits, reflecting the anisotropy of the etch. Atomic resolution AFM reveals that the sides of these hexagons are oriented along the zigzag direction of the graphite crystal lattice and the absence of the D-peak in the Raman spectrum indicates that the edges are high quality zigzag edges. In a second step of the experiment, we investigate hexagon edges created in single layer graphene on hexagonal boron nitride and find a substantial D-peak intensity. Polarization dependent Raman measurements reveal that hydrogen plasma defined edges consist of a mixture of zigzag and armchair segments. Furthermore, electronic transport measurements were performed on hydrogen plasma defined graphene nanoribbons which indicate a high quality of the bulk but a relatively low edge quality, in agreement with the Raman data. These findings are supported by tight-binding transport simulations. Hence, further optimization of the hydrogen plasma etching technique is required to obtain pure crystalline graphene edges. △ Less

Submitted 16 March, 2019; originally announced March 2019.

Comments: 10 pages, 7 figures

Journal ref: Carbon 150, 417 (May 24, 2019)

Mechanical dissipation from charge and spin transitions in oxygen deficient SrTiO_3

Authors: Marcin Kisiel, Oleg O. Brovko, Dilek Yildiz, Remy Pawlak, Urs Gysin, Erio Tosatti, Ernst Meyer

Abstract: Bodies in relative motion separated by a gap of a few nanometers can experience a tiny friction force. This non-contact dissipation can have various origins and can be successfully measured by a sensitive pendulum atomic force microscope tip oscillating laterally above the surface. Here, we report on the observation of dissipation peaks at selected voltage-dependent tip-surface distances for oxyge… ▽ More Bodies in relative motion separated by a gap of a few nanometers can experience a tiny friction force. This non-contact dissipation can have various origins and can be successfully measured by a sensitive pendulum atomic force microscope tip oscillating laterally above the surface. Here, we report on the observation of dissipation peaks at selected voltage-dependent tip-surface distances for oxygen-deficient strontium titanate (SrTiO_3) surface at low temperatures (T = 5K). The observed dissipation peaks are attributed to tip-induced charge and spin state transitions in quantum-dot-like entities formed by single oxygen vacancies (and clusters thereof, possibly through a collective mechanism) at the SrTiO_3 surface, which in view of technological and fundamental research relevance of the material opens important avenues for further studies and applications. △ Less

Submitted 14 September, 2018; originally announced September 2018.

Journal ref: Nature Communicationsvolume 9, Article number: 2946 (2018)

Transoid-to-Cisoid Conformation Changes of Single Molecules on Surfaces Triggered by Metal Coordination

Authors: Sara Freund, Rémy Pawlak, Lucas Moser, Antoine Hinaut, Roland Steiner, Nathalie Marinakis, Edwin C. Constable, Ernst Meyer, Catherine E. Housecroft, Thilo Glatzel

Abstract: Conformational isomers are stereoisomers that can interconvert over low potential barriers by rotation around a single bond. However, such bond rotation is hampered by geometrical constraints when molecules are adsorbed on surfaces. Here we show that the adsorption of 4,4'-bis(4-carboxyphenyl)-6,6'-dimethyl-2,2'-bipyridine molecules on surfaces leads to the appearance of pro-chiral single-molecule… ▽ More Conformational isomers are stereoisomers that can interconvert over low potential barriers by rotation around a single bond. However, such bond rotation is hampered by geometrical constraints when molecules are adsorbed on surfaces. Here we show that the adsorption of 4,4'-bis(4-carboxyphenyl)-6,6'-dimethyl-2,2'-bipyridine molecules on surfaces leads to the appearance of pro-chiral single-molecules on NiO(001) and to enantiopure supramolecular domains on Au(111) surfaces containing the $transoid$ molecule conformation. Upon additional Fe adatom deposition, molecules undergo a controlled interconversion from a $transoid$ to $cisoid$ conformation as a result of coordination of the Fe atoms to the 2,2'-bipyridine moieties. As confirmed by atomic force microscopy images and X-ray photoelectron spectroscopy measurements, the resulting molecular structures become irreversibly achiral. △ Less

Submitted 15 October, 2018; v1 submitted 11 July, 2018; originally announced July 2018.

Non-quantized square-root topological insulators: a realization in photonic Aharonov-Bohm cages

Authors: Mark Kremer, Ioannis Petrides, Eric Meyer, Matthias Heinrich, Oded Zilberberg, Alexander Szameit

Abstract: Topological Insulators are a novel state of matter where spectral bands are characterized by quantized topological invariants. This unique quantized non-local property commonly manifests through exotic bulk phenomena and corresponding robust boundary effects. In our work, we report a new type of topological insulator exhibiting spectral bands with non-quantized topological properties, but with a q… ▽ More Topological Insulators are a novel state of matter where spectral bands are characterized by quantized topological invariants. This unique quantized non-local property commonly manifests through exotic bulk phenomena and corresponding robust boundary effects. In our work, we report a new type of topological insulator exhibiting spectral bands with non-quantized topological properties, but with a quantization that arises in a corresponding system where the square of the Hamiltonian is taken. We provide a thorough theoretical analysis as well as an experimental demonstration based on photonic Aharonov-Bohm cages to highlight the bulk and boundary properties of this neophyte state of matter. △ Less

Submitted 14 May, 2018; originally announced May 2018.

Comments: 5 pages, 4 figures + supplementary material (8 pages, 4 figures), comments are welcome

Conformation And Mechanical Response of Spray Deposited Single Strand DNA on Gold

Authors: Remy Pawlak, J. G. Vilhena, Antoine Hinaut, Tobias Meier, Thilo Glatzel, Alexis Baratoff, Fernando Moreno-Herrero, Enrico Gnecco, Ruben Perez, Ernst Meyer

Abstract: Single molecule force spectroscopy of DNA strands adsorbed at surfaces is a powerful technique used in air or liquid environments to quantify their mechanical properties. Although the force responses are limited to unfolding events so far, single base detection might be possible in more drastic cleanliness conditions such as ultra high vacuum. Here, we report on high resolution imaging and pulling… ▽ More Single molecule force spectroscopy of DNA strands adsorbed at surfaces is a powerful technique used in air or liquid environments to quantify their mechanical properties. Although the force responses are limited to unfolding events so far, single base detection might be possible in more drastic cleanliness conditions such as ultra high vacuum. Here, we report on high resolution imaging and pulling attempts at low temperature (5K) of a single strand DNA (ssDNA) molecules composed of 20 cytosine bases adsorbed on Au(111) by scanning probe microscopy and numerical calculations. Using electrospray deposition technique, the ssDNA were successfully transferred from solution onto a surface kept in ultra high vacuum. Real space characterizations reveal that the ssDNA have an amorphous structure on gold in agreement with numerical calculations. Subsequent substrate annealing promotes the desorption of solvent molecules, DNA as individual molecules as well as the formation of DNA self assemblies. Furthermore, pulling experiments by force spectroscopy have been conducted to measure the mechanical response of the ssDNA while detaching. A periodic pattern of 0.2 to 0.3nm is observed in the force curve which arises from the stick slip of single nucleotide bases over the gold. Although an intra molecular response is obtained in the force curve, a clear distinction of each nucleotide detachment is not possible due the complex structure of ssDNA adsorbed on gold. △ Less

Submitted 5 April, 2018; v1 submitted 10 September, 2017; originally announced September 2017.

CDW slips and giant frictional dissipation peaks at the NbSe$_2$ surface

Authors: Markus Langer, Marcin Kisiel, Rémy Pawlak, Franco Pellegrini, Giuseppe E. Santoro, Renato Buzio, Andrea Gerbi, Geetha Balakrishnan, Alexis Baratoff, Erio Tosatti, Ernst Meyer

Abstract: Accessing, controlling and understanding nanoscale friction and dissipation is a crucial issue in nanotechnology, where moving elements are central. Recently, ultra-sensitive noncontact pendulum Atomic Force Microscope (AFM) succeeded in detecting the electronic friction drop caused by the onset of superconductivity in Nb, raising hopes that a wider variety of mechanisms of mechanical dissipation… ▽ More Accessing, controlling and understanding nanoscale friction and dissipation is a crucial issue in nanotechnology, where moving elements are central. Recently, ultra-sensitive noncontact pendulum Atomic Force Microscope (AFM) succeeded in detecting the electronic friction drop caused by the onset of superconductivity in Nb, raising hopes that a wider variety of mechanisms of mechanical dissipation arising from electron organization into different collective phenomena will become accessible through this unconventional surface probe. Among them, the driven phase dynamics of charge-density-waves (CDWs) represents an outstanding challenge as a source of dissipation. Here we report a striking multiplet of AFM dissipation peaks arising at nanometer distances above the surface of NbSe$_2$ - a layered compound exhibiting an incommensurate CDW. Each peak appears at a well defined tip-surface interaction force of the order of a nN, and persists until T=70K where CDW short-range order is known to disappear. A theoretical model is presented showing that the peaks are connected to tip-induced local 2$π$ CDW phase slips. Under the attractive potential of the approaching tip, the local CDW surface phase landscape deforms continuously until a series of 2$π$ jumps occur between different values of the local phase. As the tip oscillates to and fro, each slip gives rise to a hysteresis cycle, appearing at a selected distance, the dissipation corresponding to "pumping" in and out a local slip in the surface CDW phase of NbSe$_2$. △ Less

Submitted 12 May, 2016; originally announced May 2016.

Comments: 9 pages, 8 figures

Journal ref: Nature Materials 13, 173-177 (2014)

Superlubricity of Graphene Nanoribbons on Gold Surfaces

Authors: Shigeki Kawai, Andrea Benassi, Enrico Gnecco, Hajo Soede, Remy Pawlak, Xinliang Feng, Klaus Muellen, Daniele Passerone, Carlo A. Pignedoli, Pascal Ruffieux, Roman Fasel, Ernst Meyer

Abstract: The state of vanishing friction known as superlubricity has important applications for energy saving and increasing the lifetime of devices. Superlubricity detected with atomic force microscopy appears in examples like sliding large graphite flakes or gold nanoclusters across surfaces. However, the origin of the behavior is poorly understood due to the lack of a controllable nano-contact. We demon… ▽ More The state of vanishing friction known as superlubricity has important applications for energy saving and increasing the lifetime of devices. Superlubricity detected with atomic force microscopy appears in examples like sliding large graphite flakes or gold nanoclusters across surfaces. However, the origin of the behavior is poorly understood due to the lack of a controllable nano-contact. We demonstrate graphene nanoribbons superlubricity when sliding on gold with a joint experimental and computational approach. The atomically well-defined contact allows us to trace the origin of superlubricity, unravelling the role played by edges, surface reconstruction and ribbon elasticity. Our results pave the way to the scale-up of superlubricity toward the realization of frictionless coatings. △ Less

Submitted 13 March, 2016; originally announced March 2016.

Comments: Corresponding authors E-mail: shigeki.kawai@unibas.ch and andrea.benassi@nano.tu-dresden.de

Journal ref: Science 351 957-961 (2016)

Noncontact dissipation reveals critical central peak in SrTiO3

Authors: M. Kisiel, F. Pellegrini, G. E. Santoro, M. Samadashvili, R. Pawlak, A. Benassi, U. Gysin, R. Buzio, A. Gerbi, E. Meyer, E. Tosatti

Abstract: The critical fluctuations at second order structural transitions in a bulk crystal may affect the dissipation of mechanical probes even if completely external to the crystal surface. Here we show that noncontact force microscope dissipation bears clear evidence of the antiferrodistortive phase transition of SrTiO3, known for a long time to exhibit a unique, extremely narrow neutron scattering "cen… ▽ More The critical fluctuations at second order structural transitions in a bulk crystal may affect the dissipation of mechanical probes even if completely external to the crystal surface. Here we show that noncontact force microscope dissipation bears clear evidence of the antiferrodistortive phase transition of SrTiO3, known for a long time to exhibit a unique, extremely narrow neutron scattering "central peak". The noncontact geometry suggests a central peak linear response coupling connected with strain. The detailed temperature dependence reveals for the first time the intrinsic central peak width of order 80 kHz, two orders of magnitude below the established neutron upper bound. △ Less

Submitted 3 June, 2015; originally announced June 2015.

Comments: 5 pages, 3 figures

Journal ref: Physical Review Letters 115 046101 (2015)

Probing Atomic Structure and Majorana Wavefunctions in Mono-Atomic Fe-chains on Superconducting Pb-Surface

Authors: Remy Pawlak, Marcin Kisiel, Jelena Klinovaja, Tobias Meier, Shigeki Kawai, Thilo Glatzel, Daniel Loss, Ernst Meyer

Abstract: Motivated by the striking promise of quantum computation, Majorana bound states (MBSs) in solid-state systems have attracted wide attention in recent years. In particular, the wavefunction localization of MBSs is a key feature and crucial for their future implementation as qubits. Here, we investigate the spatial and electronic characteristics of topological superconducting chains of iron atoms on… ▽ More Motivated by the striking promise of quantum computation, Majorana bound states (MBSs) in solid-state systems have attracted wide attention in recent years. In particular, the wavefunction localization of MBSs is a key feature and crucial for their future implementation as qubits. Here, we investigate the spatial and electronic characteristics of topological superconducting chains of iron atoms on the surface of Pb(110) by combining scanning tunneling microscopy (STM) and atomic force microscopy (AFM). We demonstrate that the Fe chains are mono-atomic, structured in a linear fashion, and exhibit zero-bias conductance peaks at their ends which we interprete as signature for a Majorana bound state. Spatially resolved conductance maps of the atomic chains reveal that the MBSs are well localized at the chain ends (below 25 nm), with two localization lengths as predicted by theory. Our observation lends strong support to use MBSs in Fe chains as qubits for quantum computing devices. △ Less

Submitted 21 August, 2015; v1 submitted 22 May, 2015; originally announced May 2015.

Comments: 13 pages, 3 figures

Journal ref: npj Quantum Information 2, 16035 (2016)

Pico- and nanosecond laser ablation of mixed tungsten / aluminium films

Authors: M. Wisse, L. Marot, R. Steiner, D. Mathys, A. Stumpp, M. Joanny, J. M. Travere, E. Meyer

Abstract: In order to extend the investigation of laser-assisted cleaning of ITER-relevant first mirror materials to the picosecond regime, a commercial laser system delivering 10 picosecond pulses at 355 nm at a frequency of up to 1 MHz has been used to investigate the ablation of mixed aluminium (oxide) / tungsten (oxide) layers deposited on poly- and nanocrystalline molybdenum as well as nanocrystalline… ▽ More In order to extend the investigation of laser-assisted cleaning of ITER-relevant first mirror materials to the picosecond regime, a commercial laser system delivering 10 picosecond pulses at 355 nm at a frequency of up to 1 MHz has been used to investigate the ablation of mixed aluminium (oxide) / tungsten (oxide) layers deposited on poly- and nanocrystalline molybdenum as well as nanocrystalline rhodium mirrors. Characterization before and after cleaning using scanning electron microscopy (SEM) and spectrophotometry shows heavy dust formation, resulting in a degradation of the reflectivity. Cleaning using a 5 nanosecond pulses at 350 and 532 nm, on the other hand, proved very promising. The structure of the film remnants suggests that in this case buckling was the underlying removal mechanism rather than ablation. Repeated coating and cleaning using nanosecond pulses is demonstrated. △ Less

Submitted 17 April, 2014; originally announced April 2014.

Comments: Accepted in Fusion Science and Technology. Fusion Science and Technology 2014

Lateral vibration effects in atomic-scale friction

Authors: R. Roth, O. Y. Fajardo, J. J. Mazo, E. Meyer, E. Gnecco

Abstract: The influence of lateral vibrations on the stick-slip motion of a nanotip elastically pulled on a flat crystal surface is studied by atomic force microscopy (AFM) measurements on a NaCl(001) surface in ultra-high vacuum. The slippage of the nanotip across the crystal lattice is anticipated at increasing driving amplitude, similarly to what is observed in presence of normal vibrations. This lowers… ▽ More The influence of lateral vibrations on the stick-slip motion of a nanotip elastically pulled on a flat crystal surface is studied by atomic force microscopy (AFM) measurements on a NaCl(001) surface in ultra-high vacuum. The slippage of the nanotip across the crystal lattice is anticipated at increasing driving amplitude, similarly to what is observed in presence of normal vibrations. This lowers the average friction force, as explained by the Prandtl-Tomlinson model with lateral vibrations superimposed at finite temperature. Nevertheless, the peak values of the lateral force, and the total energy losses, are expected to increase with the excitation amplitude, which may limit the practical relevance of this effect. △ Less

Submitted 14 February, 2014; originally announced February 2014.

Comments: To appear in Applied Physics Letters

A Multi-scale Approach for Simulations of Kelvin Probe Force Microscopy with Atomic Resolution

Authors: Ali Sadeghi, Alexis Baratoff, S. Alireza Ghasemi, Stefan Goedecker, Thilo Glatzel, Shigeki Kawai, Ernst Meyer

Abstract: The distance dependence and atomic-scale contrast observed in nominal contact potential difference (CPD) signals recorded by KPFM on surfaces of insulating and semiconducting samples, have stimulated theoretical attempts to explain such effects. We attack this problem in two steps. First, the electrostatics of the macroscopic tip-cantilever-sample system is treated by a finite-difference method on… ▽ More The distance dependence and atomic-scale contrast observed in nominal contact potential difference (CPD) signals recorded by KPFM on surfaces of insulating and semiconducting samples, have stimulated theoretical attempts to explain such effects. We attack this problem in two steps. First, the electrostatics of the macroscopic tip-cantilever-sample system is treated by a finite-difference method on an adjustable nonuniform mesh. Then the resulting electric field under the tip apex is inserted into a series of atomistic wavelet-based density functional theory (DFT) calculations. Results are shown for a realistic neutral but reactive silicon nano-scale tip interacting with a NaCl(001) sample. Bias-dependent forces and resulting atomic displacements are computed to within an unprecedented accuracy. Theoretical expressions for amplitude modulation (AM) and frequency modulation (FM) KPFM signals and for the corresponding local contact potential differences (LCPD) are obtained by combining the macroscopic and atomistic contributions to the electrostatic force component generated at the voltage modulation frequency, and evaluated for several tip oscillation amplitudes A up to 10 nm. Being essentially constant over a few Volts, the slope of atomistic force versus bias is the basic quantity which determines variations of the atomic-scale LCPD contrast. Already above A = 0.1 nm, the LCPD contrasts in both modes exhibit almost the same spatial dependence as the slope. In the AM mode, this contrast is approximately proportional to $A^{-1/2}$, but remains much weaker than the contrast in the FM mode, which drops somewhat faster as A is increased. These trends are a consequence of the macroscopic contributions to the KPFM signal, which are stronger in the AM-mode and especially important if the sample is an insulator even at sub-nanometer separations where atomic-scale contrast appears. △ Less

Submitted 24 March, 2012; originally announced March 2012.

Comments: 19 pages, 13 figures

Molecular Dynamics Simulations of Dynamic Force Microscopy: Applications to the Si(111)-7x7 Surface

Authors: Abduxukur Abdurixit, Alexis Baratoff, Ernest Meyer

Abstract: Molecular dynamics simulations have been performed to understand true atomic resolution, which has been observed on the Si(111)-7$\times$7 surface by dynamic force microscopy in ultra high vacuum(UHV). Stable atomic-scale contrast is reproduced in simulations at constant mean height above a critical tip-sample separation when monitoring the interaction force between tip and sample. Missing or ad… ▽ More Molecular dynamics simulations have been performed to understand true atomic resolution, which has been observed on the Si(111)-7$\times$7 surface by dynamic force microscopy in ultra high vacuum(UHV). Stable atomic-scale contrast is reproduced in simulations at constant mean height above a critical tip-sample separation when monitoring the interaction force between tip and sample. Missing or additional adatoms can be recognized in such scans, although they are less well resolved than native adatoms. The resonance frequency shift, as well as arbitrary scans, e.g. at constant force can be computed from a series of force-distance characteristics. By means of dynamic simulations we show how energy losses induced by interaction with an oscillating tip can be monitored and that they occur even in the non-contact range. △ Less

Submitted 1 March, 2000; originally announced March 2000.

Comments: 5 pages, 5 figures, accepted publication in Applied Surface Science

Monte Carlo Renormalization of the 3-D Ising model: Analyticity and Convergence

Authors: H. W. J. Blöte, J. R. Heringa, A. Hoogland, E. W. Meyer, T. S. Smit

Abstract: We review the assumptions on which the Monte Carlo renormalization technique is based, in particular the analyticity of the block spin transformations. On this basis, we select an optimized Kadanoff blocking rule in combination with the simulation of a d=3 Ising model with reduced corrections to scaling. This is achieved by including interactions with second and third neighbors. As a consequence… ▽ More We review the assumptions on which the Monte Carlo renormalization technique is based, in particular the analyticity of the block spin transformations. On this basis, we select an optimized Kadanoff blocking rule in combination with the simulation of a d=3 Ising model with reduced corrections to scaling. This is achieved by including interactions with second and third neighbors. As a consequence of the improved analyticity properties, this Monte Carlo renormalization method yields a fast convergence and a high accuracy. The results for the critical exponents are y_H=2.481(1) and y_T=1.585(3). △ Less

Submitted 5 February, 1996; originally announced February 1996.

Comments: RevTeX, 4 PostScript files