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Manipulation of localized excitons in CrPS$_4$ by temperature and magnetic field
Authors:
Dipankar Jana,
Swagata Acharya,
Amit Pawbake,
Dmitrii Litvinov,
Aljoscha Soll,
Zdenek Sofer,
Clement Faugeras,
Dimitar Pashov,
Mark van Schilfgaarde,
Kostya S. Novoselov,
Marek Potemski,
Maciej Koperski
Abstract:
Layered van der Waals magnetic semiconductors provide a versatile platform for exploring excitonic phenomena intertwined with spin and lattice degrees of freedom, enabling excitons to act as sensitive probes of magnetic order. CrPS$_4$ is a layered antiferromagnetic semiconductor that hosts rich excitonic features whose microscopic origin and connection to magnetic ordering remain incompletely und…
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Layered van der Waals magnetic semiconductors provide a versatile platform for exploring excitonic phenomena intertwined with spin and lattice degrees of freedom, enabling excitons to act as sensitive probes of magnetic order. CrPS$_4$ is a layered antiferromagnetic semiconductor that hosts rich excitonic features whose microscopic origin and connection to magnetic ordering remain incompletely understood. Here, we investigate the electronic and excitonic properties of bulk CrPS$_4$ using a combination of many-body perturbation theory, dynamical mean-field theory, and photoluminescence-based experiments. Our calculations establish CrPS$_4$ as a direct-gap semiconductor with a bandgap of 2.48~eV in the antiferromagnetic phase. Several sub-bandgap excitonic transitions are predicted by theory, comprising multiple spin-allowed excitons and an additional spin-flip excitation, predominantly localized on the Cr$^{3+}$ ions. Temperature- and magnetic-field-dependent optical measurements reveal thermally driven exciton redistribution among localized states and identify characteristic energy shifts that provide clear optical signatures of magnetic phase transitions in CrPS$_4$. These results provide new insights into the excitonic transitions of antiferromagnets and suggest potential routes for all-optical sensing and light-driven control of their magnetic order.
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Submitted 4 August, 2026;
originally announced August 2026.
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Visualization of Defect Electronic States in Layered Semiconductor CrSBr
Authors:
Jonathan Brunette,
Joost Aretz,
Kiyoung Jo,
Aljoscha Soll,
Zdeněk Sofer,
Malte Rösner,
Nathan Guisinger,
Adina Luican-Mayer
Abstract:
Chromium sulfur bromide (CrSBr) is a layered magnetic semiconducting material combining a rich magnetic phase diagram with axis-dependent electronic and optical properties. While defects in CrSBr have been shown to affect magnetic order and excitonic responses, their microscopic nature, atomic structure, and electronic properties are not yet fully understood. In this work, we use scanning tunnelin…
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Chromium sulfur bromide (CrSBr) is a layered magnetic semiconducting material combining a rich magnetic phase diagram with axis-dependent electronic and optical properties. While defects in CrSBr have been shown to affect magnetic order and excitonic responses, their microscopic nature, atomic structure, and electronic properties are not yet fully understood. In this work, we use scanning tunneling microscopy/spectroscopy (STM/STS) to explore the structure and electronic signatures of two prominent defects in bulk CrSBr. Their structure reflects the symmetries of the underlying lattice, with electronic features near the valence band edge. By comparing experimental data with ab initio simulated STM images, we infer that a common defect corresponds to a b-axis-aligned double sulfur vacancy, in line with findings from a recent growth analysis study. This result advances our understanding of the role of intrinsic defects in shaping the electronic structure of CrSBr.
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Submitted 23 July, 2026;
originally announced July 2026.
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Spin-flip optical excitations in van der Waals antiferromagnet CrPS$_4$
Authors:
Dipankar Jana,
Aljoscha Soll,
Zdenek Sofer,
Milan Orlita,
Clement Faugeras,
Maciej Koperski,
Marek Potemski
Abstract:
We investigate the near-infrared optical response of the semiconducting van der Waals antiferromagnet CrPS$_4$ and identify previously unreported spin-entangled optical resonances. The strong and anisotropic magnetic-field dependence of these resonances reflects the underlying magnetic order and confirms the biaxial antiferromagnetic nature of CrPS$_4$. From the magnetic field evolution of the opt…
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We investigate the near-infrared optical response of the semiconducting van der Waals antiferromagnet CrPS$_4$ and identify previously unreported spin-entangled optical resonances. The strong and anisotropic magnetic-field dependence of these resonances reflects the underlying magnetic order and confirms the biaxial antiferromagnetic nature of CrPS$_4$. From the magnetic field evolution of the optical transition, we extract key magnetic parameters, including the spin-flop ($\approx0.9$~T) and spin-saturation ($\approx8$~T) fields. These results demonstrate a potential pathway for all-optical probing of spin states in van der Waals antiferromagnets, with relevance for spin-sensitive optoelectronic and magneto-optical devices.
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Submitted 24 June, 2026;
originally announced June 2026.
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Direct Nanoscale Pyroelectric Characterization of a CuInP${}_2$S${}_6$ van der Waals Nanogenerator
Authors:
Valentin Fonck,
Roop K. Mech,
Mohammadali Razeghi,
Stuart Finch,
Aljoscha Söll,
Phillip Dobson,
Jonathan R. Weaver,
Zdenek Sofer,
Oleg Kolosov,
Jean Spièce,
Pascal Gehring
Abstract:
Pyroelectric energy conversion offers a route for harvesting time-dependent thermalfluctuations that are abundant in natural and technological environments. Twodimensional ferroelectrics are particularly attractive for this purpose because reduced dimensionality enables ultrathin, mechanically compliant device architectures. Here, we demonstrate direct nanoscale pyroelectric characterization of an…
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Pyroelectric energy conversion offers a route for harvesting time-dependent thermalfluctuations that are abundant in natural and technological environments. Twodimensional ferroelectrics are particularly attractive for this purpose because reduced dimensionality enables ultrathin, mechanically compliant device architectures. Here, we demonstrate direct nanoscale pyroelectric characterization of an out-of-plane van der Waals nanogenerator based on CuInP2S6 (CIPS) encapsulated between few-layer graphene electrodes. A scanning thermal microscopy (SThM) probe is employed as a localized nanoscale heat source while the electrically generated response is measured in situ through the device electrodes. Harmonic detection isolates the pyroelectric signal from parasitic first-harmonic electromechanical contributions, while finite-element thermal modeling combined with probe calibration enables direct determination of the local pyroelectric coefficient from the measured electrical response. Beyond quantitative characterization, the spatially resolved measurements directly identify electrically inactive regions associated with device defects, revealing local performance-limiting features that remain hidden in conventional spatially averaged pyroelectric measurements. The presented approach establishes a versatile platform for quantitative nanoscale pyroelectric characterization and the optimization of van der Waals pyroelectric devices.
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Submitted 22 June, 2026; v1 submitted 15 June, 2026;
originally announced June 2026.
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Interplay of Cl Substitution and He$^{+}$ Irradiation in CrSBr$_{1-x}$Cl$_{x}$
Authors:
Satyam Sahu,
Adeel Bukhari,
Arijit Kayal,
Valerie Černá,
Bing Wu,
Aljoscha Söll,
Gregor Hlawacek,
Zdeněk Sofer,
Martin Kalbáč,
Matěj Velický,
Otakar Frank
Abstract:
Two-dimensional magnetic semiconductors provide a promising platform for exploring the interplay between disorder, lattice dynamics, and resonant light--matter interactions. Among them, CrSBr exhibits strong in-plane anisotropy and pronounced resonance-enhanced Raman scattering. Here, we investigate the effects of Cl substitution and He$^{+}$ irradiation on the vibrational response of CrSBr using…
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Two-dimensional magnetic semiconductors provide a promising platform for exploring the interplay between disorder, lattice dynamics, and resonant light--matter interactions. Among them, CrSBr exhibits strong in-plane anisotropy and pronounced resonance-enhanced Raman scattering. Here, we investigate the effects of Cl substitution and He$^{+}$ irradiation on the vibrational response of CrSBr using polarization-resolved Raman spectroscopy. Cl substitution activates additional phonon modes associated with local symmetry breaking, while He$^{+}$ irradiation introduces distinct defect-related scattering channels and enhanced phonon broadening. The combined effects of alloy disorder and externally introduced defects lead to strong anisotropic reconstruction of the Raman spectra and modification of the nonlinear Raman response under near-resonant 1.96 eV excitation. Power-dependent measurements reveal robust superlinear scaling of both intrinsic and substitution-induced phonon modes, indicating persistent resonance-enhanced electron--phonon coupling even in defect-engineered samples.
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Submitted 29 May, 2026;
originally announced May 2026.
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Deep-Subwavelength and Broadband Quarter-Wave Retardation in Ultrathin Hyperbolic MoOCl2
Authors:
Georgy Ermolaev,
Adilet Toksumakov,
Valeria Maslova,
Aleksandr Slavich,
Anton Minnekhanov,
Gleb Tselikov,
Nikolay Pak,
Andrey Vyshnevyy,
Aljoscha Söll,
Zdeněk Sofer,
Aleksey Arsenin,
Kostya S. Novoselov,
Valentyn Volkov
Abstract:
The miniaturization of polarization-controlling optical components is one of the central pursuits in nanophotonics. While traditional anisotropic materials require large propagation lengths to achieve the desired phase shifts, metasurfaces mitigate this size constraint but often introduce narrow operational bandwidths and high fabrication complexities. To bridge this gap, we introduce MoOCl2 as a…
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The miniaturization of polarization-controlling optical components is one of the central pursuits in nanophotonics. While traditional anisotropic materials require large propagation lengths to achieve the desired phase shifts, metasurfaces mitigate this size constraint but often introduce narrow operational bandwidths and high fabrication complexities. To bridge this gap, we introduce MoOCl2 as a promising material for ultracompact and broadband phase retardation. Building on its giant optical anisotropy, we experimentally demonstrate MoOCl2 quarter-wave plates with thicknesses of 77 nm and 98 nm. These flakes exhibit achromatic quarter-wave retardation across broad visible (445 - 525 nm) and near-infrared (730 - 945 nm) spectral windows, surpassing the fundamental thickness and bandwidth limitations of both conventional optical materials and artificial nanostructures. Moreover, MoOCl2 waveplates demonstrate up to lambda/4500 retardance tolerance at central wavelengths. As a result, this study establishes MoOCl2 as a building block for ultracompact polarization optics.
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Submitted 6 April, 2026;
originally announced April 2026.
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Dielectric Tensor of CrSBr from Spectroscopic Imaging Ellipsometry
Authors:
Pierre-Maurice Piel,
Sebastian Schaper,
Aleksandra Łopion,
Jakob Henz,
Aljoscha Soll,
Zdenek Sofer,
Ursula Wurstbauer
Abstract:
Chromium sulfur bromide (CrSBr) is a magnetic van der Waals semiconductor with a direct bandgap and pronounced anisotropy in its electronic, optical, spin and lattice degrees of freedom. Here, we employ spectroscopic imaging ellipsometry (SIE) and Mueller-matrix analysis to determine the full dielectric tensor of paramagnetic CrSBr thin films. Our measurements reveal optical anisotropy, characteri…
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Chromium sulfur bromide (CrSBr) is a magnetic van der Waals semiconductor with a direct bandgap and pronounced anisotropy in its electronic, optical, spin and lattice degrees of freedom. Here, we employ spectroscopic imaging ellipsometry (SIE) and Mueller-matrix analysis to determine the full dielectric tensor of paramagnetic CrSBr thin films. Our measurements reveal optical anisotropy, characterized by three distinct diagonal components of the dielectric tensor. The in-plane elements are dominated by prominent excitonic resonances polarized along the two main crystallographic axes. Two main excitonic bands (A and B excitons) centered around 1.3eV and 1.7eV, respectively, are identified; the A-exciton polarized along the b-crystallographic direction, whereas the B-exciton appears to consist of two nearly degenerate contributions polarized along two orthogonal in-plane crystal axes. These results provide fundamental insight into anisotropic light-matter interactions in CrSBr, relevant for future spin-optoelectronic and photonic applications.
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Submitted 23 March, 2026; v1 submitted 11 March, 2026;
originally announced March 2026.
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Robust phonon engineering and symmetry-selective lattice dynamics in CrSBr$_{1-x}$Cl$_{x}$
Authors:
Satyam Sahu,
Arsalan Hashemi,
Mahdi Ghorbani-Asl,
János Koltai,
Jan Maňák,
Bing Wu,
Aljoscha Söll,
Zdeněk Sofer,
Mikko Karttunen,
Arkady V. Krasheninnikov,
Matěj Velický,
Otakar Frank
Abstract:
Atomic substitution provides a controlled route to engineer lattice dynamics in low-symmetry two-dimensional materials. Here, by combining polarization-resolved Raman spectroscopy and first-principles calculations, we investigate the evolution of phonon characteristics in CrSBr$_{1-x}$Cl$_{x}$ ($0 \leq x \leq \sim 0.5$) upon partial substitution of Br with Cl atoms. Progressive Cl substitution of…
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Atomic substitution provides a controlled route to engineer lattice dynamics in low-symmetry two-dimensional materials. Here, by combining polarization-resolved Raman spectroscopy and first-principles calculations, we investigate the evolution of phonon characteristics in CrSBr$_{1-x}$Cl$_{x}$ ($0 \leq x \leq \sim 0.5$) upon partial substitution of Br with Cl atoms. Progressive Cl substitution of Br induces systematic shifts of parent CrSBr out-of-plane $A_\textrm{g}$ phonon modes and activates additional Raman features. These features persist across different polarization configurations and excitation energies, reflecting substitution-induced symmetry lowering and local lattice perturbations. Explicit supercell phonon calculations combined with Raman $Γ$-density-of-states simulations identify these features as symmetry-lowered descendants of parent modes arising from alloy disorder. Complementary strain-dependent calculations reveal that anisotropic lattice compression plays a key role in renormalizing Cr-S dominated phonons. Under near-resonant excitation, stimulated Raman scattering-like amplification remains observable with increasing Cl content, highlighting the resilience of anisotropic electron-phonon coupling in this system.
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Submitted 19 January, 2026;
originally announced January 2026.
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Van der Waals CrSBr alloys with tunable magnetic and optical properties
Authors:
Shalini Badola,
Amit Pawbake,
Bing Wu,
Aljosha Söll,
Zdenek Sofer,
Rolf Heid,
Clement Faugeras
Abstract:
Van der Waals magnets are attracting a lot of attention for their potential integration in spintronic and magnonic technologies. CrSBr is an A-type antiferromagnet that shows a coupling between its electronic band structure and magnetic properties. This property is appealing for applications and it also offers the possibility to investigate magnetic ground states and GHz magnons using visible opti…
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Van der Waals magnets are attracting a lot of attention for their potential integration in spintronic and magnonic technologies. CrSBr is an A-type antiferromagnet that shows a coupling between its electronic band structure and magnetic properties. This property is appealing for applications and it also offers the possibility to investigate magnetic ground states and GHz magnons using visible optics techniques. Using Raman scattering and (magneto)-optical experiments, we describe the magnetic and optical properties of alloys of CrSBr$_{(1-x)}$Cl$_x$ with $x<0.46$. Similar to CrSBr, these alloys are direct band gap semiconductors with a coupling of their electronic and magnetic properties. Exciton energies evolve weakly with composition and we describe the large changes in the saturation magnetic fields and their implications on the magnetic properties. We show that both the interlayer magnetic exchange and electronic interactions are modified by the halogen mixing, offering the possibility to tune magnon energies with alloy composition.
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Submitted 5 January, 2026;
originally announced January 2026.
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Anisotropic Phonon Dynamics and Directional Transport in Actinide van der Waals Semiconductor USe$_3$
Authors:
Aljoscha Söll,
Valentino Jadrisko,
Sourav Dey,
Nassima Benchtaber,
Kalyan Sarkar,
Borna Radatovic,
Jan Luxa,
Fedor Lipilin,
Kseniia Mosina,
Vojtech Kundrat,
Jakub Zalesak,
Jana Vejpravova,
Martin Zacek,
Christoph Gadermaier,
José J. Baldoví,
Zdeněk Sofer
Abstract:
Direction-dependent charge transport and optical responses are characteristic of van der Waals (vdW) materials with strong in-plane anisotropy. While transition-metal trichalcogenides (TMTCs) exemplify this behavior, heavier analogs remain largely unexplored. In this study we examine USe$_3$ as an anisotropic vdW material and a heavier analog of the well-studied TMTCs. We reveal strong in-plane an…
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Direction-dependent charge transport and optical responses are characteristic of van der Waals (vdW) materials with strong in-plane anisotropy. While transition-metal trichalcogenides (TMTCs) exemplify this behavior, heavier analogs remain largely unexplored. In this study we examine USe$_3$ as an anisotropic vdW material and a heavier analog of the well-studied TMTCs. We reveal strong in-plane anisotropy using polarization-resolved Raman spectroscopy, investigate strain-induced shifts of phonon modes, and quantify direction-dependent charge-carrier mobility through transport measurements on field-effect devices. First-principles calculations based on density-functional theory corroborate our findings, providing a theoretical basis for our experimental observations. Casting USe$_3$ as an actinide analog of a TMTC establishes a platform for exploring low-dimensional semiconductors that combine strong in-plane anisotropy with f-electron physics.
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Submitted 3 December, 2025;
originally announced December 2025.
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Electron-magnon coupling at the interface of a "twin-twisted" antiferromagnet
Authors:
Yue Sun,
Fanhao Meng,
Sijia Ke,
Kun Xu,
Hongrui Zhang,
Aljoscha Soll,
Zdeněk Sofer,
Arun Majumdar,
Ramamoorthy Ramesh,
Jeffrey B. Neaton,
Jie Yao,
Joseph Orenstein
Abstract:
We identify a "twin-twist" angle in orthorhombic two-dimensional magnets that maximizes interlayer orbital overlap and enables strong interfacial coupling. Focusing on the van der Waals antiferromagnet CrSBr, we show that this twist angle, near 72 deg, aligns diagonal lattice vectors across the layers, enhancing the interlayer hopping that is spin-forbidden in pristine systems and orbital-forbidde…
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We identify a "twin-twist" angle in orthorhombic two-dimensional magnets that maximizes interlayer orbital overlap and enables strong interfacial coupling. Focusing on the van der Waals antiferromagnet CrSBr, we show that this twist angle, near 72 deg, aligns diagonal lattice vectors across the layers, enhancing the interlayer hopping that is spin-forbidden in pristine systems and orbital-forbidden in 90-deg-twisted samples. The enhanced hopping modifies the electronic structure and activates a novel mechanism for excitation of interfacial magnons. Using optical probes we discover that excitons on one side of the interface selectively excite magnons localized on the opposite side. We show that this cross-coupling phenomenon can be understood as a consequence of the spin-transfer torque as that arises as electrons tunnel across the twin-twisted interface. Our findings demonstrate that large-angle twisting in anisotropic 2D materials offers a powerful tool for engineering spin and charge transport through controlled interlayer hybridization, opening new avenues for twisted magnetism and strongly correlated moiré physics.
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Submitted 11 June, 2025;
originally announced June 2025.
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Lithium Intercalation in the Anisotropic van der Waals Magnetic Semiconductor CrSBr
Authors:
Kseniia Mosina,
Aljoscha Söll,
Jiri Sturala,
Martin Veselý,
Petr Levinský,
Florian Dirnberger,
Giuliana Materzanini,
Nicola Marzari,
Gian-Marco Rignanese,
Borna Radatović,
David Sedmidubsky,
Zdeněk Sofer
Abstract:
Alkali metal intercalation is an important strategy for doping van der Waals materials. Lithium, in particular, was shown to achieve exceptional charge carrier densities, reaching levels at which fundamental electrical, optical, and magnetic material properties begin to be strongly modified. While lithium is known to be highly volatile, its migration dynamics in anisotropic layered crystals remain…
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Alkali metal intercalation is an important strategy for doping van der Waals materials. Lithium, in particular, was shown to achieve exceptional charge carrier densities, reaching levels at which fundamental electrical, optical, and magnetic material properties begin to be strongly modified. While lithium is known to be highly volatile, its migration dynamics in anisotropic layered crystals remain poorly understood. In this work, we investigate the intercalation of lithium in-between layers of the anisotropic magnetic semiconductor CrSBr. Using exfoliated crystals, we are able to monitor the dynamics of the intercalation process in real time through optical and electrical characterization methods. Our measurements reveal highly anisotropic migration of Lithium characterized by diffusion coefficients that differ by more than one order of magnitude along a- and b-directions. This finding is in good agreement with our molecular dynamics simulations which show trajectories of lithium atoms primarily follow the Br-chains in the a-direction. Beyond that, we find that partially covering CrSBr crystals by thin hexagonal boron nitride (hBN) flakes has a significant impact on the intercalation process, and that lithium strongly enhances the electrical conductivity along the a-axis. Our method offers a new platform for lithium diffusion studies and encourages further research to pursue the fabrication of lithium-doped devices.
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Submitted 21 May, 2025;
originally announced May 2025.
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Colossal magneto-excitonic effects in 2D van der Waals magnetic semiconductor CrSBr
Authors:
R. Komar,
M. Goryca,
A. Łopion,
M. Rybak,
T. Woźniak,
M. Raczyński,
K. M. Gałązka,
K. Mosina,
A. Söll,
Z. Sofer,
W. Pacuski,
C. Faugeras,
M. Birowska,
P. Kossacki,
T. Kazimierczuk
Abstract:
2D magnetic semiconductors, which intrinsically couple a rich landscape of magnetic orders with tightly bound electron-hole pairs (excitons), present an exciting platform to investigate the interplay between optical and magnetic phenomena at the atomic scale. In such systems, the strength of magneto-optical effects determines how deeply the magnetic properties can be revealed. Here, we report the…
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2D magnetic semiconductors, which intrinsically couple a rich landscape of magnetic orders with tightly bound electron-hole pairs (excitons), present an exciting platform to investigate the interplay between optical and magnetic phenomena at the atomic scale. In such systems, the strength of magneto-optical effects determines how deeply the magnetic properties can be revealed. Here, we report the observation of remarkably strong magneto-excitonic effects in the 2D magnetic semiconductor CrSBr that allow probing its magnetic order with unprecedented sensitivity. By investigating optical transitions above the fundamental exciton energy, we discover a massive spectral shift approaching 100 meV under applied magnetic fields - an order of magnitude larger than previously observed magneto-excitonic responses. Our comprehensive magneto-optical experiments accompanied by detailed DFT calculations indicate the possible origin of the transitions exhibiting such intriguing behavior. These findings open avenues for exploiting magneto-excitonic phenomena at newly accessible regimes, enabling novel opto-spintronic applications previously limited by weak magnetic responses.
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Submitted 8 June, 2026; v1 submitted 30 August, 2024;
originally announced September 2024.
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Universal spin wavepacket transport in van der Waals antiferromagnets
Authors:
Yue Sun,
Fanhao Meng,
Changmin Lee,
Aljoscha Soll,
Hongrui Zhang,
Ramamoorthy Ramesh,
Jie Yao,
Zdenĕk Sofer,
Joseph Orenstein
Abstract:
Antiferromagnets (AFMs) are promising platforms for the transmission of quantum information via magnons (the quanta of spin waves), offering advantages over ferromagnets with regard to dissipation, speed of response, and immunity to external fields. Recently, it was shown that in the insulating van der Waals (vdW) semiconductor, CrSBr, strong spin-exciton coupling enables readout of magnon density…
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Antiferromagnets (AFMs) are promising platforms for the transmission of quantum information via magnons (the quanta of spin waves), offering advantages over ferromagnets with regard to dissipation, speed of response, and immunity to external fields. Recently, it was shown that in the insulating van der Waals (vdW) semiconductor, CrSBr, strong spin-exciton coupling enables readout of magnon density and propagation using photons of visible light. This exciting observation came with a puzzle: photogenerated magnons were observed to propagate 10$^3$ times faster than the velocity inferred from neutron scattering, leading to a conjecture that spin wavepackets are carried along by coupling to much faster elastic modes. Here we show, through a combination of theory and experiment, that the propagation mechanism is, instead, coupling within the magnetic degrees of freedom through long range dipole-dipole coupling. This mechanism is an inevitable consequence of Maxwell's equations, and as such, will dominate the propagation of spin at long wavelengths in the entire class of vdW magnets currently under intense investigation. Moreover, identifying the mechanism of spin propagation provides a set of optimization rules, as well as caveats, that are essential for any future applications of these promising systems.
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Submitted 6 September, 2023;
originally announced September 2023.
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Strong Exciton-Phonon Coupling as a Fingerprint of Magnetic Ordering in van der Waals Layered CrSBr
Authors:
Kaiman Lin,
Xiaoxiao Sun,
Florian Dirnberger,
Yi Li,
Jiang Qu,
Peiting Wen,
Zdenek Sofer,
Aljoscha Söll,
Stephan Winnerl,
Manfred Helm,
Shengqiang Zhou,
Yaping Dan,
Slawomir Prucnal
Abstract:
The layered, air-stable van der Waals antiferromagnetic compound CrSBr exhibits pronounced coupling between its optical, electronic, and magnetic properties. As an example, exciton dynamics can be significantly influenced by lattice vibrations through exciton-phonon coupling. Using low-temperature photoluminescence spectroscopy, we demonstrate the effective coupling between excitons and phonons in…
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The layered, air-stable van der Waals antiferromagnetic compound CrSBr exhibits pronounced coupling between its optical, electronic, and magnetic properties. As an example, exciton dynamics can be significantly influenced by lattice vibrations through exciton-phonon coupling. Using low-temperature photoluminescence spectroscopy, we demonstrate the effective coupling between excitons and phonons in nanometer-thick CrSBr. By careful analysis, we identify that the satellite peaks predominantly arise from the interaction between the exciton and an optical phonon with a frequency of 118 cm-1 (~14.6 meV) due to the out-of-plane vibration of Br atoms. Power-dependent and temperature-dependent photoluminescence measurements support exciton-phonon coupling and indicate a coupling between magnetic and optical properties, suggesting the possibility of carrier localization in the material. The presence of strong coupling between the exciton and the lattice may have important implications for the design of light-matter interactions in magnetic semiconductors and provides new insights into the exciton dynamics in CrSBr. This highlights the potential for exploiting exciton-phonon coupling to control the optical properties of layered antiferromagnetic materials.
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Submitted 31 January, 2024; v1 submitted 9 August, 2023;
originally announced August 2023.
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A high-$κ$ wide-gap layered dielectric for two-dimensional van der Waals heterostructures
Authors:
A. Söll,
E. Lopriore,
A. K. Ottesen,
J. Luxa,
G. Pasquale,
J. Sturala,
F. Hájek,
V. Jarý,
D. Sedmidubský,
K. Mosina,
A. Kis,
Z. Sofer
Abstract:
Van der Waals heterostructures of two-dimensional materials have opened up new frontiers in condensed matter physics, unlocking unexplored possibilities in electronic and photonic device applications. However, the investigation of wide-gap high-$κ$ layered dielectrics for devices based on van der Waals structures has been relatively limited. In this work, we demonstrate an easily reproducible synt…
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Van der Waals heterostructures of two-dimensional materials have opened up new frontiers in condensed matter physics, unlocking unexplored possibilities in electronic and photonic device applications. However, the investigation of wide-gap high-$κ$ layered dielectrics for devices based on van der Waals structures has been relatively limited. In this work, we demonstrate an easily reproducible synthesis method for the rare earth oxyhalide LaOBr, and we exfoliate it as a 2D layered material with a measured static dielectric constant of $ε_{0, \perp} \simeq 9$ and a wide bandgap of 5.3 eV. Furthermore, our research demonstrates that LaOBr can be used as a high-$κ$ dielectric in van der Waals field-effect transistors with high performance and low interface defect concentrations. Additionally, it proves to be an attractive choice for electrical gating in excitonic devices based on 2D materials. Our work demonstrates the versatile realization and functionality of 2D systems with wide-gap and high-$κ$ van der Waals dielectric environments.
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Submitted 25 July, 2023;
originally announced July 2023.
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Magneto-optical sensing of the pressure driven magnetic ground states in bulk CrSBr
Authors:
A. Pawbake,
T. Pelini,
I. Mohelsky,
D. Jana,
I. Breslavetz,
C. -W. Cho,
M. Orlita,
M. Potemski,
M. -A. Measson,
N. Wilson,
K. Mosina,
A. Soll,
Z. Sofer,
B. A. Piot,
M. E. Zhitomirsky,
C. Faugeras
Abstract:
Competition between exchange interactions and magnetocrystalline anisotropy may bring new magnetic states that are of great current interest. An applied hydrostatic pressure can further be used to tune their balance. In this work we investigate the magnetization process of a biaxial antiferromagnet in an external magnetic field applied along the easy axis. We find that the single metamagnetic tran…
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Competition between exchange interactions and magnetocrystalline anisotropy may bring new magnetic states that are of great current interest. An applied hydrostatic pressure can further be used to tune their balance. In this work we investigate the magnetization process of a biaxial antiferromagnet in an external magnetic field applied along the easy axis. We find that the single metamagnetic transition of the Ising type observed in this material under ambient pressure transforms under hydrostatic pressure into two transitions, a first-order spin flop transition followed by a second order transition towards a polarized ferromagnetic state near saturation. This reversible tuning into a new magnetic phase is obtained in layered bulk CrSBr at low temperature by varying the interlayer distance using high hydrostatic pressure, which efficiently acts on the interlayer magnetic exchange, and is probed by magneto-optical spectroscopy.
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Submitted 24 October, 2023; v1 submitted 3 March, 2023;
originally announced March 2023.
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Layer-dependent interlayer antiferromagnetic spin reorientation in air-stable semiconductor CrSBr
Authors:
Chen Ye,
Cong Wang,
Qiong Wu,
Sheng Liu,
Jiayuan Zhou,
Guopeng Wang,
Aljoscha Soll,
Zdenek Sofer,
Ming Yue,
Xue Liu,
Mingliang Tian,
Qihua Xiong,
Wei Ji,
X. Renshaw Wang
Abstract:
Magnetic van der Waals (vdW) materials offer a fantastic platform to investigate and exploit rich spin configurations stabilized in reduced dimensions. One tantalizing magnetic order is the interlayer antiferromagnetism in A-type vdW antiferromagnet, which may be effectively modified by the magnetic field, stacking order and thickness scaling. However, atomically revealing the interlayer spin orie…
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Magnetic van der Waals (vdW) materials offer a fantastic platform to investigate and exploit rich spin configurations stabilized in reduced dimensions. One tantalizing magnetic order is the interlayer antiferromagnetism in A-type vdW antiferromagnet, which may be effectively modified by the magnetic field, stacking order and thickness scaling. However, atomically revealing the interlayer spin orientation in the vdW antiferromagnet is highly challenging, because most of the material candidates exhibit an insulating ground state or instability in ambient conditions. Here, we report the layer-dependent interlayer antiferromagnetic reorientation in air-stable semiconductor CrSBr using magnetotransport characterization and first-principles calculations. We reveal a pronounced odd-even layer effect of interlayer reorientation, which originates from the competitions among interlayer exchange, magnetic anisotropy energy and extra Zeeman energy of uncompensated magnetization. Furthermore, we quantitatively constructed the layer-dependent magnetic phase diagram with the help of a linear-chain model. Our work uncovers the layer-dependent interlayer antiferromagnetic reorientation engineered by magnetic field in the air-stable semiconductor, which could contribute to future vdW spintronic devices.
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Submitted 20 May, 2022; v1 submitted 11 May, 2022;
originally announced May 2022.