We study the ground state of an S=1/2 anisotropic a (≡Jz/Jxy) Heisenberg antiferromagnet with nearest (J1) and next-nearest (J2) neighbor exchange interactions on a triangular lattice using the exact diagonalization ...We study the ground state of an S=1/2 anisotropic a (≡Jz/Jxy) Heisenberg antiferromagnet with nearest (J1) and next-nearest (J2) neighbor exchange interactions on a triangular lattice using the exact diagonalization method. We obtain the energy, squared sublattice magnetizations, and their Binder ratios on finite lattices with N≤36 sites. We estimate the threshold J(t) 2 (a)?between the three-sublattice Néel state and the spin liquid (SL) state, and J(s) 2 (a)? between the stripe state and the SL state. The SL state exists over a wide range in the α-J2 plane. For α>1 , the xy component of the magnetization is destroyed by quantum fluctuations, and the classical distorted 120°structure is replaced by the collinear state.展开更多
Polycrystalline samples of a novel spin-liquid compound Tb2Ti2O7 were prepared by a standard solid-state reaction. X-ray diffraction at room temperature confirms that the synthesized compound of Tb2Ti2O7 is single pha...Polycrystalline samples of a novel spin-liquid compound Tb2Ti2O7 were prepared by a standard solid-state reaction. X-ray diffraction at room temperature confirms that the synthesized compound of Tb2Ti2O7 is single phase with cubic unit cell constant a0 of 1.015 44 nm. Magnetic susceptibility measurements in the temperature range between 100 and 300 K give an effective moment of 9.44 μB and Curie-Weiss temperature of 12.68 K, respectively, indicating the dominance of antiferromagnetic interactions. However, below 50 K, the magnetic behavior of Tb2Ti2O7 deviates from Curie-Weiss law, whose origin remains suspicion.展开更多
Quantum fluctuations from frustration can trigger quantum spin liquids(QSLs) at zero temperature.However, it is unclear how thermal fluctuations affect a QSL. We employ state-of-the-art tensor network-based methods to...Quantum fluctuations from frustration can trigger quantum spin liquids(QSLs) at zero temperature.However, it is unclear how thermal fluctuations affect a QSL. We employ state-of-the-art tensor network-based methods to explore the ground state and thermodynamic properties of the spin-1=2 kagomé Heisenberg antiferromagnet(KHA). Its ground state is shown to be consistent with a gapless QSL by observing the absence of zero-magnetization plateau as well as the algebraic behaviors of susceptibility and specific heat at low temperatures, respectively. We show that there exists an algebraic paramagnetic liquid(APL) that possesses both the paramagnetic properties and the algebraic behaviors inherited from the QSL. The APL is induced under the interplay between quantum fluctuations from geometrical frustration and thermal fluctuations. By studying the temperature-dependent behaviors of specific heat and magnetic susceptibility, a finite-temperature phase diagram in a magnetic field is suggested, where various phases are identified. This present study gains useful insight into the thermodynamic properties of the spin-1/2 KHA with or without a magnetic field and is helpful for relevant experimental studies.展开更多
The discovery of ideal spin-1/2 kagome antiferromagnets Herbertsmithite and Zn-doped Barlowite represents a breakthrough in the quest for quantum spin liquids(QSLs),and nuclear magnetic resonance(NMR)spectroscopy play...The discovery of ideal spin-1/2 kagome antiferromagnets Herbertsmithite and Zn-doped Barlowite represents a breakthrough in the quest for quantum spin liquids(QSLs),and nuclear magnetic resonance(NMR)spectroscopy plays a prominent role in revealing the quantum paramagnetism in these compounds.However,interpretation of NMR data that is often masked by defects can be controversial.Here,we show that the most significant interaction strength for NMR,i.e.the hyperfine coupling(HFC)strength,can be reasonably reproduced by first-principles calculations for these proposed QSLs.Applying this method to a supercell containing Cu-Zn defects enables us to map out the variation and distribution of HFC at different nuclear sites.This predictive power is expected to bridge the missing link in the analysis of the low-temperature NMR data.展开更多
We construct a class of exactly solvable generalized Kitaev spin-1/2 models in arbitrary dimensions, which is beyond the category of quantum compass models. The Jordan-Wigner transformation is employed to prove the ex...We construct a class of exactly solvable generalized Kitaev spin-1/2 models in arbitrary dimensions, which is beyond the category of quantum compass models. The Jordan-Wigner transformation is employed to prove the exact solvability. An exactly solvable quantum spin-1/2 model can be mapped to a gas of free Majorana fermions coupled to static Z2 gauge fields. We classify these exactly solvable models according to their parent models. Any model belonging to this class can be generated by one of the parent models. For illustration, a two dimensional(2D) tetragon-octagon model and a three dimensional(3D) xy bond model are studied.展开更多
The magnetic properties of two-dimensional antiferromagnet NiGa2S4 have attracted much attention and yet some problems are far from being solved. We investigate the magnetic properties of NiGa2S4 by Monte Carlo simula...The magnetic properties of two-dimensional antiferromagnet NiGa2S4 have attracted much attention and yet some problems are far from being solved. We investigate the magnetic properties of NiGa2S4 by Monte Carlo simulations. A new spin-interacting model is proposed to describe the system, and the specific heat together with the doping effect of nonmagnetic impurity is studied by simulations. The double peaks of the specific heat as well as other behaviors are well reproduced. We also compare our results with those of other models, and the underlying physics is discussed.展开更多
Discovering more and new geometrically frustrated systems remains an active point of inquiry in fundamental physics for the existence of unusual states of matter.Here,we report spin-liquid-like behavior in a two-dimen...Discovering more and new geometrically frustrated systems remains an active point of inquiry in fundamental physics for the existence of unusual states of matter.Here,we report spin-liquid-like behavior in a two-dimensional(2D)rhombic lattice Fe-metal-organic framework(Fe-MOF)with frustrated antiferromagnetism.This Fe-MOF exhibits a high frustration factor f=|θCW|/TN≥315,and its long-range magnetic order is suppressed down to 180 mK.Detailed theoretical calculations demonstrate strong antiferromagnetic coupling between adjacent Fe3+ions,indicating the potential of a classical spin-liquid-like behavior.Notably,a T-linear heat capacity parameter,γ,originating from electronic contributions and with magnetic field independence up to 8 T,can be observed in the specific heat capacity measurements at low-temperature,providing further proof for the spin-liquid-like behavior.This work highlights the potential of MOF materials in geometrically frustrated systems,and will promote the research of exotic quantum physics phenomena.展开更多
Subject Code:A04With the support by the National Natural Science Foundation of China and the Ministry of Science and Technology of China,the research team led by Prof.Zhao Jun(赵俊)and Prof.Chen Gang(陈钢)at the State...Subject Code:A04With the support by the National Natural Science Foundation of China and the Ministry of Science and Technology of China,the research team led by Prof.Zhao Jun(赵俊)and Prof.Chen Gang(陈钢)at the State Key Laboratory of Surface Physics and Department of Physics,Fudan University,found evidence for aquantum spin liquid state with a spinon Fermi surface in YbMgGaO_4,which was published in Nature(2016,540:559—562);see also'News and Views'Nature(2016,540:534—535).展开更多
Subject Code:A04Frustrated quantum magnets have developed into one of the hottest topics in condensed matter physics because of the wide range of novel physical phenomena they exhibit,which includes quantum spin-liqui...Subject Code:A04Frustrated quantum magnets have developed into one of the hottest topics in condensed matter physics because of the wide range of novel physical phenomena they exhibit,which includes quantum spin-liquid states,fractionalized spin degrees of freedom,and exotic topological properties.This trend is展开更多
文摘We study the ground state of an S=1/2 anisotropic a (≡Jz/Jxy) Heisenberg antiferromagnet with nearest (J1) and next-nearest (J2) neighbor exchange interactions on a triangular lattice using the exact diagonalization method. We obtain the energy, squared sublattice magnetizations, and their Binder ratios on finite lattices with N≤36 sites. We estimate the threshold J(t) 2 (a)?between the three-sublattice Néel state and the spin liquid (SL) state, and J(s) 2 (a)? between the stripe state and the SL state. The SL state exists over a wide range in the α-J2 plane. For α>1 , the xy component of the magnetization is destroyed by quantum fluctuations, and the classical distorted 120°structure is replaced by the collinear state.
基金Supported by the National Natural Science Foundation of China (1047074)
文摘Polycrystalline samples of a novel spin-liquid compound Tb2Ti2O7 were prepared by a standard solid-state reaction. X-ray diffraction at room temperature confirms that the synthesized compound of Tb2Ti2O7 is single phase with cubic unit cell constant a0 of 1.015 44 nm. Magnetic susceptibility measurements in the temperature range between 100 and 300 K give an effective moment of 9.44 μB and Curie-Weiss temperature of 12.68 K, respectively, indicating the dominance of antiferromagnetic interactions. However, below 50 K, the magnetic behavior of Tb2Ti2O7 deviates from Curie-Weiss law, whose origin remains suspicion.
基金supported in part by the National Key R&D Program of China (2018YFA0305800)the National Natural Science Foundation of China (14474279 and 11834014)+5 种基金and the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB28000000 and XDB07010100)SJR was supported by ERC AdG OSYRIS (ERC-2013-AdG Grant No. 339106)Spanish Ministry MINECO (National Plan 15 Grant: FISICATEAMO No. FIS201679508-P, SEVERO OCHOA No. SEV-2015-0522)Generalitat de Catalunya (AGAUR Grant No. 2017 SGR 1341 and CERCA/Program)Fundació Privada Cellex, EU FETPRO QUIC (H2020-FETPROACT2014 No. 641122)the National Science Centre, and PolandSymfonia Grant No. 2016/20/W/ST4/00314
文摘Quantum fluctuations from frustration can trigger quantum spin liquids(QSLs) at zero temperature.However, it is unclear how thermal fluctuations affect a QSL. We employ state-of-the-art tensor network-based methods to explore the ground state and thermodynamic properties of the spin-1=2 kagomé Heisenberg antiferromagnet(KHA). Its ground state is shown to be consistent with a gapless QSL by observing the absence of zero-magnetization plateau as well as the algebraic behaviors of susceptibility and specific heat at low temperatures, respectively. We show that there exists an algebraic paramagnetic liquid(APL) that possesses both the paramagnetic properties and the algebraic behaviors inherited from the QSL. The APL is induced under the interplay between quantum fluctuations from geometrical frustration and thermal fluctuations. By studying the temperature-dependent behaviors of specific heat and magnetic susceptibility, a finite-temperature phase diagram in a magnetic field is suggested, where various phases are identified. This present study gains useful insight into the thermodynamic properties of the spin-1/2 KHA with or without a magnetic field and is helpful for relevant experimental studies.
基金supported by National Key Projects for Research and Development of China with Grant No. 2021YFA1400400the National Natural Science Foundation of China with Grants No. 12225407 and 12074174+2 种基金China Postdoctoral Science Foundation with Grants No. 2022M711569 and 2022T150315Jiangsu Province Excellent Postdoctoral Program with Grant No. 20220ZB5Fundamental Research Funds for the Central Universities
基金supported by the National Natural Science Foundation of China(11774196)Tsinghua University Initiative Scientific Research Program+5 种基金supported by the National Postdoctoral Program for Innovative Talents of China(BX201600091)the Funding from China Postdoctoral Science Foundation(2017M610858)the support from US-DOE(DEFG02-04ER46148)supported by National Key Research and Development Program of China(2016YFA0300202)National Natural Science Foundation of China(11774306)the Strategic Priority Research Program of Chinese Academy of Sciences(XDB28000000)
文摘The discovery of ideal spin-1/2 kagome antiferromagnets Herbertsmithite and Zn-doped Barlowite represents a breakthrough in the quest for quantum spin liquids(QSLs),and nuclear magnetic resonance(NMR)spectroscopy plays a prominent role in revealing the quantum paramagnetism in these compounds.However,interpretation of NMR data that is often masked by defects can be controversial.Here,we show that the most significant interaction strength for NMR,i.e.the hyperfine coupling(HFC)strength,can be reasonably reproduced by first-principles calculations for these proposed QSLs.Applying this method to a supercell containing Cu-Zn defects enables us to map out the variation and distribution of HFC at different nuclear sites.This predictive power is expected to bridge the missing link in the analysis of the low-temperature NMR data.
基金the China Postdoctoral Science Foundation of China(Grant No.2017M620880)the National Natural Science Foundation of China(Grant No.1184700424)+7 种基金the National Key Research and Development Program of China(Grant No.2016YFA0300202)the National Basic Research Program of China(Grant No.2014CB921201)the National Natural Science Foundation of Chino(Grant No.11774306)the Key Research Program of the Chinese Academy of Sciences(Grant No.XDPB08-4)the Fundamental Research Funds for the Central Universities in Chinathe National Natural Science Foundation of China(Grant No.11674278)the National Basic Research Program of China(Grant No.2014CB921203)the CAS Center for Excellence in Topological Quantum Computation.
文摘We construct a class of exactly solvable generalized Kitaev spin-1/2 models in arbitrary dimensions, which is beyond the category of quantum compass models. The Jordan-Wigner transformation is employed to prove the exact solvability. An exactly solvable quantum spin-1/2 model can be mapped to a gas of free Majorana fermions coupled to static Z2 gauge fields. We classify these exactly solvable models according to their parent models. Any model belonging to this class can be generated by one of the parent models. For illustration, a two dimensional(2D) tetragon-octagon model and a three dimensional(3D) xy bond model are studied.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11247428,11247210,10974228,and 61274101)the Natural Science Foundation of Liaoning Province,China(Grant No.20121078)the Education Office of Liaoning Province,China(Grant No.L201197)
文摘The magnetic properties of two-dimensional antiferromagnet NiGa2S4 have attracted much attention and yet some problems are far from being solved. We investigate the magnetic properties of NiGa2S4 by Monte Carlo simulations. A new spin-interacting model is proposed to describe the system, and the specific heat together with the doping effect of nonmagnetic impurity is studied by simulations. The double peaks of the specific heat as well as other behaviors are well reproduced. We also compare our results with those of other models, and the underlying physics is discussed.
基金supported by the National Key Research and Development Program of China Nos.2016YFA0300503the National Natural Science Foundation of China No.11774061the Shanghai Municipal Science and Technology(Major Project Grant No.2019SHZDZX01 and No.20ZR1405300).
基金supported by the National Key Research and Development Program of China(No.2021YFA1600800)the National Natural Science Foundation of China(Nos.11975234,12075243,12005227,12105286,121350122,U2032150,12275271,12205305,and U1932211)+5 种基金the Natural Science Foundation of Anhui Province(Nos.2208085QA14 and 2208085J13)the Users with Excellence Program of Hefei Science Center CAS(Nos.2020HSC-UE002,2020HSC-CIP013,2021HSC-UE002,and 2021HSC-UE003)the Major science and technology project of Anhui Province(No.202103a05020025)the Key Program of Research and Development of Hefei Science Center,CAS(Nos.2021HSC-KPRD002 and 2021HSC-KPRD003)the Fundamental Research Funds for the Central Universities(No.WK 2310000103)partially carried out at the USTC Center for Micro and Nanoscale Research and Fabrication.
文摘Discovering more and new geometrically frustrated systems remains an active point of inquiry in fundamental physics for the existence of unusual states of matter.Here,we report spin-liquid-like behavior in a two-dimensional(2D)rhombic lattice Fe-metal-organic framework(Fe-MOF)with frustrated antiferromagnetism.This Fe-MOF exhibits a high frustration factor f=|θCW|/TN≥315,and its long-range magnetic order is suppressed down to 180 mK.Detailed theoretical calculations demonstrate strong antiferromagnetic coupling between adjacent Fe3+ions,indicating the potential of a classical spin-liquid-like behavior.Notably,a T-linear heat capacity parameter,γ,originating from electronic contributions and with magnetic field independence up to 8 T,can be observed in the specific heat capacity measurements at low-temperature,providing further proof for the spin-liquid-like behavior.This work highlights the potential of MOF materials in geometrically frustrated systems,and will promote the research of exotic quantum physics phenomena.
文摘Subject Code:A04With the support by the National Natural Science Foundation of China and the Ministry of Science and Technology of China,the research team led by Prof.Zhao Jun(赵俊)and Prof.Chen Gang(陈钢)at the State Key Laboratory of Surface Physics and Department of Physics,Fudan University,found evidence for aquantum spin liquid state with a spinon Fermi surface in YbMgGaO_4,which was published in Nature(2016,540:559—562);see also'News and Views'Nature(2016,540:534—535).
文摘Subject Code:A04Frustrated quantum magnets have developed into one of the hottest topics in condensed matter physics because of the wide range of novel physical phenomena they exhibit,which includes quantum spin-liquid states,fractionalized spin degrees of freedom,and exotic topological properties.This trend is
