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Evolution of the superconductivity in pressurized La3-xSmxNi2O7
Authors:
Qingyi Zhong,
Junfeng Chen,
Zhengyang Qiu,
Jingyuan Li,
Xing Huang,
Peiyue Ma,
Mengwu Huo,
Hongliang Dong,
Hualei Sun,
Meng Wang
Abstract:
Motivated by the discovery of superconductivity in bilayer La$_3$Ni$_2$O$_7$ at 80 K and the increased superconducting transition temperature, $T_\text{c}$, up to 92 K in single crystals of La$_2$SmNi$_2$O$_7$ under pressure, we systematically study the effect of Sm doping on the superconductivity and structure of La$_{3-x}$Sm$_x$Ni$_2$O$_7$ (0 $\leq$ x $\leq$ 1.5) under pressure. Experimental inv…
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Motivated by the discovery of superconductivity in bilayer La$_3$Ni$_2$O$_7$ at 80 K and the increased superconducting transition temperature, $T_\text{c}$, up to 92 K in single crystals of La$_2$SmNi$_2$O$_7$ under pressure, we systematically study the effect of Sm doping on the superconductivity and structure of La$_{3-x}$Sm$_x$Ni$_2$O$_7$ (0 $\leq$ x $\leq$ 1.5) under pressure. Experimental investigations in polycrystalline samples reveal that Sm doping monotonically decreases the lattice constants $c$ and $a$, thereby enhancing crystal structure distortion and leading to an evolution of the metallic ground state in La$_3$Ni$_2$O$_7$ to an insulating state in La$_{1.5}$Sm$_{1.5}$Ni$_2$O$_7$. The maximum onset $T_\text{c}$ in compounds $x=0.9$ and 1.5 is 89 K, while the pressure that drives the emergence of superconductivity is higher for higher doping levels. The results suggest that the enhancement of $T_\text{c}$ in La$_{3-x}$Sm$_x$Ni$_2$O$_7$ is mainly affected by the compressed $c$ lattice before saturation, and the structure transition is critical for the emergence of superconductivity. Our experimental results provide insight into the influence of elemental substitution on nickelate superconductors, offering a means to increase the transition temperature further.
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Submitted 15 October, 2025;
originally announced October 2025.
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Interlayer coupling enhanced superconductivity near 100 K in La$_{3-x}$Nd$_x$Ni$_2$O$_7$
Authors:
Zhengyang Qiu,
Junfeng Chen,
Dmitrii V. Semenok,
Qingyi Zhong,
Di Zhou,
Jingyuan Li,
Peiyue Ma,
Xing Huang,
Mengwu Huo,
Tao Xie,
Xiang Chen,
Ho-kwang Mao,
Viktor Struzhkin,
Hualei Sun,
Meng Wang
Abstract:
Systematically controlling the superconducting transition temperature ($T_\text{c}$) in the bilayer Ruddlesden-Popper nickelate La$_3$Ni$_2$O$_7$ remains a significant challenge. Here, we address this by synthesizing high-quality polycrystalline La$_{3-x}$Nd$_x$Ni$_2$O$_7$ ($0 \leq x \leq 2.4$) with record-level rare-earth substitution. Nd doping compresses the lattice, particularly along the $c$…
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Systematically controlling the superconducting transition temperature ($T_\text{c}$) in the bilayer Ruddlesden-Popper nickelate La$_3$Ni$_2$O$_7$ remains a significant challenge. Here, we address this by synthesizing high-quality polycrystalline La$_{3-x}$Nd$_x$Ni$_2$O$_7$ ($0 \leq x \leq 2.4$) with record-level rare-earth substitution. Nd doping compresses the lattice, particularly along the $c$ axis, enhances the spin density wave transition temperature, and elevates the pressure required for the orthorhombic-to-tetragonal structural transition. Superconductivity is observed across all doping levels under high pressures, with the onset $T_\text{c}$ rising to $\sim$93~K for $x = 2.1$ and $2.4$ from the electronic transport measurement. Using the radio-frequency transmission technique, newly applied to nickelate superconductors, we detect signatures of superconductivity at $98 \pm 2$~K in the $x=2.4$ compound, pushing the $T_\text{c}$ frontier further. We identify a universal linear relationship where $T_\text{c}$ decreases with the $c$-axis lattice parameter at a rate of approximately $-28$~K/Å, demonstrating that enhanced interlayer magnetic exchange coupling is the dominant mechanism for superconducting pairing. Our work establishes the critical role of magnetism and provides a unified structural descriptor for elevating $T_\text{c}$ in bilayer nickelates.
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Submitted 14 October, 2025;
originally announced October 2025.
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Observation of Topological Armchair Edge States in Photonic Biphenylene Network
Authors:
Qi Zhong,
Yongsheng Liang,
Shiqi Xia,
Daohong Song,
Zhigang Chen
Abstract:
Edge states in 2D materials are vital for advancements in spintronics, quantum computing, and logic transistors. For graphene nanoribbons, it is well known that the zigzag edges can host edge states, but realization of armchair edge states has been challenging without breaking the time-reversal symmetry. Here, by using a photonic analog of recently synthesized graphene-like biphenylene network (BP…
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Edge states in 2D materials are vital for advancements in spintronics, quantum computing, and logic transistors. For graphene nanoribbons, it is well known that the zigzag edges can host edge states, but realization of armchair edge states has been challenging without breaking the time-reversal symmetry. Here, by using a photonic analog of recently synthesized graphene-like biphenylene network (BPN), we demonstrate topological in-gap edge states particularly at the armchair edges. Interestingly, several bulk states preserve the characteristics of edge states along the armchair boundaries, manifesting an unusual hybridization between the edge and bulk states. Experimentally, we observe both zigzag and armchair edge states in photonic BPN lattices written in a nonlinear crystal. Furthermore, we clarify the different features of the armchair boundary between the BPN and graphene lattices. Our results demonstrated here may be applicable to carbon-based BPNs and other artificial platforms beyond photonics, holding promise for expanding the application scope of 2D materials.
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Submitted 11 March, 2025;
originally announced March 2025.
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Resolving the topology of encircling multiple exceptional points
Authors:
Chitres Guria,
Qi Zhong,
Sahin K. Ozdemir,
Yogesh S. S. Patil,
Ramy El-Ganainy,
Jack G. E. Harris
Abstract:
Non-Hermiticity has emerged as a new paradigm for controlling coupled-mode systems in ways that cannot be achieved with conventional techniques. One aspect of this control that has received considerable attention recently is the encircling of exceptional points (EPs). To date, most work has focused on systems consisting of two modes that are tuned by two control parameters and have isolated EPs. W…
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Non-Hermiticity has emerged as a new paradigm for controlling coupled-mode systems in ways that cannot be achieved with conventional techniques. One aspect of this control that has received considerable attention recently is the encircling of exceptional points (EPs). To date, most work has focused on systems consisting of two modes that are tuned by two control parameters and have isolated EPs. While these systems exhibit exotic features related to EP encircling, it has been shown that richer behavior occurs in systems with more than two modes. Such systems can be tuned by more than two control parameters, and contain EPs that form a knot-like structure. Control loops that encircle this structure cause the system's eigenvalues to trace out non-commutative braids. Here we consider a hybrid scenario: a three-mode system with just two control parameters. We describe the relationship between control loops and their topology in the full and two-dimensional parameter space. We demonstrate this relationship experimentally using a three-mode mechanical system in which the control parameters are provided by optomechanical interaction with a high-finesse optical cavity.
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Submitted 16 February, 2024; v1 submitted 6 April, 2023;
originally announced April 2023.
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One Dimensional Nearly Free Electron States in Borophene
Authors:
Longjuan Kong,
Liren Liu,
Lan Chen,
Qing Zhong,
Peng Cheng,
Hui Li,
Zhuhua Zhang,
Kehui Wu
Abstract:
Two-dimensional boron (borophene) is featured by its structural polymorphs and distinct in-plane anisotropy, opening opportunities to achieve tailored electronic properties by intermixing different phases. Here, using scanning tunneling spectroscopy combined with first-principles calculations, delocalized one-dimensional nearly free electron states (NFE) in the (2,3) or \b{eta}12 borophene sheet o…
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Two-dimensional boron (borophene) is featured by its structural polymorphs and distinct in-plane anisotropy, opening opportunities to achieve tailored electronic properties by intermixing different phases. Here, using scanning tunneling spectroscopy combined with first-principles calculations, delocalized one-dimensional nearly free electron states (NFE) in the (2,3) or \b{eta}12 borophene sheet on the Ag(111) surface were observed. The NFE states emerge from a line defect in the borophene, manifested as a structural unit of the (2,2) or \c{hi}3 sheet, which creates an in-plane potential well that shifts the states toward the Fermi level. The NFE states are held in the 2D plane of borophene, rather than in the vacuum region as observed in other nanostructures. Furthermore the borophene can provide a rare prototype to further study novel NFE behaviors, which may have potential applications on transport or field emission nanodevices based on boron.
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Submitted 21 April, 2019;
originally announced April 2019.
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Strain-Induced Band Engineering in Monolayer Stanene on Sb(111)
Authors:
Jian Gou,
Longjuan Kong,
Hui Li,
Qing Zhong,
Wenbin Li,
Peng Cheng,
Lan Chen,
Kehui Wu
Abstract:
Two-dimensional (2D) allotrope of tin with low buckled honeycomb structure, named as stanene, is proposed to be an ideal 2D topological insulator with a nontrivial gap larger than 0.1 eV. Theoretical works also pointed out the topological property of stanene occurs by strain tuning. In this letter, we report the successful realization of high quality, monolayer stanene film as well as monolayer st…
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Two-dimensional (2D) allotrope of tin with low buckled honeycomb structure, named as stanene, is proposed to be an ideal 2D topological insulator with a nontrivial gap larger than 0.1 eV. Theoretical works also pointed out the topological property of stanene occurs by strain tuning. In this letter, we report the successful realization of high quality, monolayer stanene film as well as monolayer stanene nanoribbons on Sb(111) surface by molecular beam epitaxy, providing an ideal platform to the study of stanene. More importantly, we observed a continuous evolution of the electronic bands of stanene across a nanoribbon, which are related to the strain field gradient in stanene. Our work experimentally confirmed that strain is an effective method for band engineering in stanene, which is important for fundamental research and application of stanene.
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Submitted 29 June, 2017;
originally announced June 2017.
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Synthesis of Borophene Nanoribbons on Ag(110) Surface
Authors:
Qing Zhong,
Longjuan Kong,
Jian Gou,
Wenbin Li,
Shaoxiang Sheng,
Shuo Yang,
Peng Cheng,
Hui Li,
Kehui Wu,
Lan Chen
Abstract:
We present the successful synthesis of single-atom-thick borophene nanoribbons (BNRs) by self-assembly of boron on Ag(110) surface. The scanning tunneling microscopy (STM) studies reveal high quality BNRs: all the ribbons are along the [-110] direction of Ag(110), and can run across the steps on the surface. The width of ribbons is distributed in a narrow range around 10.3 nm. High resolution STM…
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We present the successful synthesis of single-atom-thick borophene nanoribbons (BNRs) by self-assembly of boron on Ag(110) surface. The scanning tunneling microscopy (STM) studies reveal high quality BNRs: all the ribbons are along the [-110] direction of Ag(110), and can run across the steps on the surface. The width of ribbons is distributed in a narrow range around 10.3 nm. High resolution STM images revealed four ordered surface structures in BNRs. Combined with DFT calculations, we found that all the four structures of boron nanoribbons consist of the boron chains with different width, separated by hexagonal hole arrays. The successful synthesis of BNRs enriches the low dimensional allotrope of boron and may promote further applications of borophene
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Submitted 18 April, 2017;
originally announced April 2017.
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Experimental Realization of Two-Dimensional Boron Sheets
Authors:
Baojie Feng,
Jin Zhang,
Qing Zhong,
Wenbin Li,
Shuai Li,
Hui Li,
Peng Cheng,
Sheng Meng,
Lan Chen,
Kehui Wu
Abstract:
Boron is the fifth element in the periodic table and possesses rich chemistry second only to carbon. A striking feature of boron is that B12 icosahedral cages occur as the building blocks in bulk boron and many boron compounds. This is in contrast to its neighboring element, carbon, which prefers 2D layered structure (graphite) in its bulk form. On the other hand, boron clusters of medium size hav…
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Boron is the fifth element in the periodic table and possesses rich chemistry second only to carbon. A striking feature of boron is that B12 icosahedral cages occur as the building blocks in bulk boron and many boron compounds. This is in contrast to its neighboring element, carbon, which prefers 2D layered structure (graphite) in its bulk form. On the other hand, boron clusters of medium size have been predicted to be planar or quasi-planar, such as B12+ , B13+, B19-, B36, and so on. This is also in contrast to carbon clusters which exhibit various cage structures (fullerenes). Therefore, boron and carbon can be viewed as a set of complementary chemical systems in their bulk and cluster structures. Now, with the boom of graphene, an intriguing question is that whether boron can also form a monoatomic-layer 2D sheet structure? Here, we report the first successful experimental realization of 2D boron sheets. We have revealed two types of boron sheet structures, corresponding to a triangular boron lattice with different arrangements of the hexagonal holes. Moreover, our boron sheets were found to be relatively stable against oxidization, and interacts only weekly with the substrate. The realization of such a long expected 2D boron sheet could open a door toward boron electronics, in analogous to the carbon electronics based on graphene.
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Submitted 15 December, 2015;
originally announced December 2015.
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Bandgap Controlling of the Oxygen-Vacancy-Induced Two-Dimensional Electron Gas in SrTiO3
Authors:
Z. Q. Liu,
W. Lu,
S. W. Zeng,
J. W. Deng,
Z. Huang,
C. J. Li,
M. Motapothula,
W. M. Lü,
L. Sun,
K. Han,
J. Q. Zhong,
P. Yang,
N. N. Bao,
W. Chen,
J. S. Chen,
Y. P. Feng,
J. M. D. Coey,
T. Venkatesan,
Ariando
Abstract:
We report very large bandgap enhancement in SrTiO3 (STO) films (fabricated by pulsed laser deposition below 800 °C), which can be up to 20% greater than the bulk value, depending on the deposition temperature. The origin is comprehensively investigated and finally attributed to Sr/Ti antisite point defects, supported by density functional theory calculations. More importantly, the bandgap enhancem…
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We report very large bandgap enhancement in SrTiO3 (STO) films (fabricated by pulsed laser deposition below 800 °C), which can be up to 20% greater than the bulk value, depending on the deposition temperature. The origin is comprehensively investigated and finally attributed to Sr/Ti antisite point defects, supported by density functional theory calculations. More importantly, the bandgap enhancement can be utilized to tailor the electronic and magnetic phases of the two-dimensional electron gas (2DEG) in STO-based interface systems. For example, the oxygen-vacancy-induced 2DEG (2DEG-V) at the interface between amorphous LaAlO3 and STO films is more localized and the ferromagnetic order in the STO-film-based 2DEG-V can be clearly seen from low-temperature magnetotransport measurements. This opens an attractive path to tailor electronic, magnetic and optical properties of STO-based oxide interface systems under intensive focus in the oxide electronics community. Meanwhile, our study provides key insight into the origin of the fundamental issue that STO films are difficult to be doped into the fully metallic state by oxygen vacancies.
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Submitted 29 April, 2014; v1 submitted 28 April, 2014;
originally announced April 2014.
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Picosecond Dynamic Heterogeneity, Hopping and Johari-Goldstein Relaxation in Glassforming Liquids
Authors:
Marcus T. Cicerone,
Qin Zhong,
Madhusudan Tyagi
Abstract:
We show that incoherent quasi-elastic neutron scattering (QENS) from molecular liquids reveals a two-state dynamic heterogeneity on a 1 ps timescale, where molecules are either highly confined or are free to undergo relatively large excursions. Data ranging from deep in the glassy state to well above the melting point allows us to observe temperature-dependent population levels and exchange betwee…
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We show that incoherent quasi-elastic neutron scattering (QENS) from molecular liquids reveals a two-state dynamic heterogeneity on a 1 ps timescale, where molecules are either highly confined or are free to undergo relatively large excursions. Data ranging from deep in the glassy state to well above the melting point allows us to observe temperature-dependent population levels and exchange between these two states. A simple physical picture emerges from this data, combined with published work, that provides a mechanism for "hopping" and for the Johari-Goldstein ($β_{JG}$) relaxation, and allows us to accurately calculate the diffusion coefficient, $D_T$, and characteristic times for $α$, and $β_{JG}$ relaxations from ps timescale neutron data.
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Submitted 30 June, 2014; v1 submitted 23 October, 2013;
originally announced October 2013.
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Electronic transport in ferromagnetic barriers on the surface of a topological insulator with $δ$ doping
Authors:
Jian-Hui Yuan,
Yan Zhang,
Daizheng Huang,
Qinhu Zhong,
Xin Zhang
Abstract:
We investigate electron transporting through a two-dimensional ferromagnetic/normal/ferromagnetic tunnel junction on the surface of a three-dimensional topological insulator with taking into $δ$ doping account. It is found that the conductance oscillates with the Fermi energy, the position and the aptitude of the $δ$ doping. Also the conductance depends sensitively on the direction of the magnetiz…
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We investigate electron transporting through a two-dimensional ferromagnetic/normal/ferromagnetic tunnel junction on the surface of a three-dimensional topological insulator with taking into $δ$ doping account. It is found that the conductance oscillates with the Fermi energy, the position and the aptitude of the $δ$ doping. Also the conductance depends sensitively on the direction of the magnetization of the two ferromagnets, which originate from the control of the spin flow due to spin-momentum locked. It is found that the conductance is the maximum at the parallel configuration while it is minimum at the antiparallel configuration and vice versa, which may stem from the half wave loss due to the electron wave entering through the antiparallel configuration. These characters are very helpful for making new types of magnetoresistance devices due to the practical applications.
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Submitted 4 July, 2013;
originally announced July 2013.
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The transition from amorphous to crystalline in Al/Zr multilayers
Authors:
Qi Zhong,
Zhong Zhang,
Shuang Ma,
Runze Qi,
Jia Li,
Zhanshan Wang,
Karine Le Guen,
Jean-Michel André,
Philippe Jonnard
Abstract:
The amorphous-to-crystalline transition in Al(1.0%wtSi)/Zr and Al(Pure)/Zr multilayers grown by direct-current magnetron sputtering system has been characterized over a range of Al layer thicknesses (1.0-5.0 nm) by using a series of complementary measurements including grazing incidence X-ray reflectometry, atomic force microscopy, X-ray diffraction and high-resolution transmission electron micros…
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The amorphous-to-crystalline transition in Al(1.0%wtSi)/Zr and Al(Pure)/Zr multilayers grown by direct-current magnetron sputtering system has been characterized over a range of Al layer thicknesses (1.0-5.0 nm) by using a series of complementary measurements including grazing incidence X-ray reflectometry, atomic force microscopy, X-ray diffraction and high-resolution transmission electron microscopy. The Al layer thickness transition exhibits the Si doped in Al could not only disfavor the crystallization of Al, but also influence the changing trends of surface roughness and diffraction peak position of phase Al<111>. An interesting feature of the presence of Si in Al layer is that Si could influence the transition process in Al(1%wtSi) layer, in which the critical thickness (1.6 nm) of Al(Pure) layer in Al(Pure)/Zr shifts to 1.8 nm of Al(1.0%wtSi) layer in Al(1.0%wtSi)/Zr multilayer. We also found that the Zr-on-Al interlayer is wider than the Al-on-Zr interlayer in both systems, and the Al layers do not have specific crystal orientation in the directions vertical to the layer from SAED patterns below the thickness (3.0 nm) of Al layers. Above the thickness (3.0 nm) of Al layers, the Al layers are highly oriented in Al<111>, so that the transformation from asymmetrical to symmetrical interlayers can be observed. Based on the analysis of all measurements, we build up a model with four steps, which could explain the Al layer thickness transition process in terms of a critical thickness for the nucleation of Al(Pure) and Al(1%wtSi) crystallites.
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Submitted 27 November, 2012;
originally announced November 2012.
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Thermally induced structural modification in the Al/Zr multilayers
Authors:
Qi Zhong,
Shuang Ma,
Zhong Zhang,
Runze Qi,
Jia Li,
Zhanshan Wang,
Philippe Jonnard
Abstract:
The effect of increasing temperature on the structural stability and interactions of two kinds of Al/Zr (Al(1%wtSi)/Zr and Al(Pure)/Zr) multilayer mirrors are investigated. All Al/Zr multilayers annealed from 200^{\circ}C to 500^{\circ}C, were deposited on Si wafers by using direct-current magnetron sputtering technology. A detailed and consistent picture of the thermally induced changes in the mi…
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The effect of increasing temperature on the structural stability and interactions of two kinds of Al/Zr (Al(1%wtSi)/Zr and Al(Pure)/Zr) multilayer mirrors are investigated. All Al/Zr multilayers annealed from 200^{\circ}C to 500^{\circ}C, were deposited on Si wafers by using direct-current magnetron sputtering technology. A detailed and consistent picture of the thermally induced changes in the microstructure is obtained using an array of complementary measurements including grazing incidence X-ray reflectance, atomic force microscope, X-ray diffraction and high-resolution transmission electron microscopy. The first significant structural changes of two systems are observed at 250^{\circ}C, characterized by asymmetric interlayers appears at interface. At 290^{\circ}C, the interface consisted of amorphous Al-Zr alloy is transformed to amorphous Al-Zr alloy and cubic ZrAl3 in both systems. By 298^{\circ}C of Al(1%wtSi)/Zr and 295^{\circ}C of Al(Pure)/Zr multilayers, the interfacial phases of Al-Zr alloy transform completely into polycrystalline mixtures of hcp-ZrAl2 and cubic-ZrAl3, which smooth the interface boundary and lower the surface roughness in the multilayers. Up to 500^{\circ}C, the multilayer structure still exists in both systems, and the differences between the asymmetric interlayers are much larger in the multilayers. Finally, we discuss the transformation from symmetric to asymmetric in the annealing process for other systems.
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Submitted 24 October, 2012;
originally announced October 2012.
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Magnetic Chains Created by Polymer-Induced Assembly of Hollow Cobalt Nanoparticles
Authors:
Lin Guo,
Fang Liang,
Chen Min Liu,
Hui Bin Xu,
Qun Peng Zhong,
Xiaogang Wen,
Shihe Yang,
Wangzhi Zheng,
Chinping Chen
Abstract:
Magnetic chains of hollow cobalt nanoparticles (450-750 nm) have been synthesized by using poly(vinyl pyrrolidone) (PVP) as a template in an ethylene glycol solution. In this process, CoCl2.6H2O was reduced by N2H4.H2O in the presence of PVP. All of the Co nanoparticles are hollow with a shell of 40 nm and self-assembled into a chainlike structure that is as long as ~10 micron. At 300 K, the bra…
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Magnetic chains of hollow cobalt nanoparticles (450-750 nm) have been synthesized by using poly(vinyl pyrrolidone) (PVP) as a template in an ethylene glycol solution. In this process, CoCl2.6H2O was reduced by N2H4.H2O in the presence of PVP. All of the Co nanoparticles are hollow with a shell of 40 nm and self-assembled into a chainlike structure that is as long as ~10 micron. At 300 K, the branched hollow Co nanoparticle chains exhibit a saturation magnetization of 37.5 emu/g, a remnant magnetization of approximately 1.55 emu/g, and a coercivity of about 66 Oe, which is more than an order of magnitude larger than that of the bulk
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Submitted 9 September, 2005;
originally announced September 2005.
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Low energy and dynamical properties of a single hole in the t-Jz model
Authors:
Q. F. Zhong,
S. Sorella
Abstract:
We review in details a recently proposed technique to extract information about dynamical correlation functions of many-body hamiltonians with a few Lanczos iterations and without the limitation of finite size. We apply this technique to understand the low energy properties and the dynamical spectral weight of a simple model describing the motion of a single hole in a quantum antiferromagnet: the…
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We review in details a recently proposed technique to extract information about dynamical correlation functions of many-body hamiltonians with a few Lanczos iterations and without the limitation of finite size. We apply this technique to understand the low energy properties and the dynamical spectral weight of a simple model describing the motion of a single hole in a quantum antiferromagnet: the $t-J_z$ model in two spatial dimension and for a double chain lattice. The simplicity of the model allows us a well controlled numerical solution, especially for the two chain case. Contrary to previous approximations we have found that the single hole ground state in the infinite system is continuously connected with the Nagaoka fully polarized state for $J_z \to 0$. Analogously we have obtained an accurate determination of the dynamical spectral weight relevant for photoemission experiments. For $J_z=0$ an argument is given that the spectral weight vanishes at the Nagaoka energy faster than any power law, as supported also by a clear numerical evidence. It is also shown that spin charge decoupling is an exact property for a single hole in the Bethe lattice but does not apply to the more realistic lattices where the hole can describe closed loop paths.
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Submitted 16 January, 1995;
originally announced January 1995.
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Hole dynamics in a quantum antiferromagnet beyond the retraceable path approximation
Authors:
Q. F. Zhong,
S. Sorella,
A. Parola
Abstract:
The one-hole spectral weight for two chains and two dimensional lattices is studied numerically using a new method of analysis of the spectral function within the Lanczos iteration scheme: the Lanczos spectra decoding method. This technique is applied to the $t-J_z$ model for $J_z \to 0$, directly in the infinite size lattice. By a careful investigation of the first 13 Lanczos steps and the firs…
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The one-hole spectral weight for two chains and two dimensional lattices is studied numerically using a new method of analysis of the spectral function within the Lanczos iteration scheme: the Lanczos spectra decoding method. This technique is applied to the $t-J_z$ model for $J_z \to 0$, directly in the infinite size lattice. By a careful investigation of the first 13 Lanczos steps and the first 26 ones for the two dimensional and the two chain cases respectively, we get several new features of the one-hole spectral weight. A sharp incoherent peak with a clear momentum dispersion is identified, together with a second broad peak at higher energy. The spectral weight is finite up to the Nagaoka energy where it vanishes in a non-analytic way. Thus the lowest energy of one hole in a quantum antiferromagnet is degenerate with the Nagaoka energy in the thermodynamic limit.
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Submitted 8 December, 1993; v1 submitted 13 October, 1993;
originally announced October 1993.
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Realization of a Spin liquid in a Two Dimensional Quantum Antiferromagnet
Authors:
A. Parola,
S. Sorella,
Q. F. Zhong
Abstract:
The ground state properties of the two dimensional spatially anisotropic Heisenberg model are investigated by use of field theory mappings, spin-wave expansion and Lanczos technique. Evidence for a disorder transition induced by anisotropy at about $J_y/J_x < 0.1$ is shown. We argue that the disordered phase is gapless and its long wavelength properties can be interpreted in terms of decoupled o…
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The ground state properties of the two dimensional spatially anisotropic Heisenberg model are investigated by use of field theory mappings, spin-wave expansion and Lanczos technique. Evidence for a disorder transition induced by anisotropy at about $J_y/J_x < 0.1$ is shown. We argue that the disordered phase is gapless and its long wavelength properties can be interpreted in terms of decoupled one dimensional chains.
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Submitted 3 August, 1993;
originally announced August 1993.
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Gutzwiller-Jastrow Wavefunctions for the $1/r$ Hubbard Model
Authors:
D. F. Wang Joseph Henry,
Q. F. Zhong,
P. Coleman Serin
Abstract:
In this work, we study the wavefunctions of the one dimensional $1/r$ Hubbard model in the strong interaction limit $U =\infty$. A set of Gutzwiller-Jastorw wavefunctions are shown to be eigen-functions of the Hamiltonian. The entire excitation spectrum and the thermodynamics are also studied in terms of more generalized Jastrow wavefunctions. For the wavefunctions and integrability conditions a…
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In this work, we study the wavefunctions of the one dimensional $1/r$ Hubbard model in the strong interaction limit $U =\infty$. A set of Gutzwiller-Jastorw wavefunctions are shown to be eigen-functions of the Hamiltonian. The entire excitation spectrum and the thermodynamics are also studied in terms of more generalized Jastrow wavefunctions. For the wavefunctions and integrability conditions at finite on-site energy, further investigations are needed.
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Submitted 30 May, 1993; v1 submitted 29 May, 1993;
originally announced May 1993.