One important issue in current condensed matter physics is the search of quantum spin liquid(QSL),an exotic magnetic state with strongly-fluctuating and highly-entangled spins down to zero temperature without static o...One important issue in current condensed matter physics is the search of quantum spin liquid(QSL),an exotic magnetic state with strongly-fluctuating and highly-entangled spins down to zero temperature without static order.However,there is no consensus on the existence of a QSL state in any real material so far,due to inevitable disorder and intricate competing exchange interactions on frustrated spin lattices.Here we report systematic heat transport measurements on a honeycomb-lattice compound BaCo_(2)(AsO_(4))_(2),which manifests magnetic order in zero field.In a narrow in-plane field range after the magnetic order is nearly suppressed,in both perpendicular and parallel to the zigzag direction,a finite residual linear term of thermal conductivity is clearly observed,which is attributed to mobile fermionic excitations.In addition,the spin-phonon scattering rate exhibits a T-linear behavior when the order disappears.These observations suggest a partial QSL state with gapless spinon excitations in BaCo_(2)(AsO_(4))_(2),that emerges when a portion of the spins remains ordered,and vanishes as the spins become progressively polarized.展开更多
We report a new kagome quantum spin liquid candidate CuaZn（OH）6FBr, which does not experience any phase transition down to 50inK, more than three orders lower than the antiferromagnetic Curie-Weiss temperature （-20...We report a new kagome quantum spin liquid candidate CuaZn（OH）6FBr, which does not experience any phase transition down to 50inK, more than three orders lower than the antiferromagnetic Curie-Weiss temperature （-200 K）. A clear gap opening at low temperature is observed in the uniform spin susceptibility obtained from 19F nuclear magnetic resonance measurements. We observe the characteristic magnetic field dependence of the gap as expected for fractionalized spin-1/2 spinon excitations. Our experimental results provide firm evidence for spin fractionalization in a topologically ordered spin system, resembling charge fraetionalization in the fractional quantum Hall state.展开更多
安德森局域化是物理学中的一个基本现象,最初是安德森提出在晶体中电子受到杂质散射由于散射路径的相干导致电导完全消失,这完全来源于电子的波动特性,后来在其他各种波,如,光、微波、超声波,甚至是冷原子体系中都观察到安德森局域化现...安德森局域化是物理学中的一个基本现象,最初是安德森提出在晶体中电子受到杂质散射由于散射路径的相干导致电导完全消失,这完全来源于电子的波动特性,后来在其他各种波,如,光、微波、超声波,甚至是冷原子体系中都观察到安德森局域化现象。在晶体中,除电子外,还可能存在各种各样的磁激发准粒子,但是对于这些磁性准粒子的安德森局域化研究几乎没有。我们测量了苯甲酸铜Cu(C6H5COO)2·3H2O这个一维反铁磁海森堡链单晶的极低温比热和热导率,发现一直到50 m K的极低温,spinon磁性准粒子对比热都有一个恒定的线性贡献项Cs/T,但是其热导率的线性贡献项ks/T只保持不变到300 m K。在300m K以下,ks/T迅速减小,到100 m K以下就基本消失了。实验结果是spinon安德森局域化的一个较强的证据,为在凝聚态物理中研究安德森局域化现象开辟了一个新的窗口。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
Spin excitation continua observed in neutron scattering studies are often considered to be strong evidence of quantum spin liquid formation.In a disorder-free magnetic compound with a quantum spin liquid ground state,...Spin excitation continua observed in neutron scattering studies are often considered to be strong evidence of quantum spin liquid formation.In a disorder-free magnetic compound with a quantum spin liquid ground state,the elementary excitation is no longer the conventional spin waves(magnons).Instead,the magnons fractionalize into spinons,producing a characteristic two-spinon continuum.However,it remained uncertain whether a clean,ordered antiferromagnet could exhibit a continuous spectrum similar to that of a quantum spin liquid.This paper presents evidence of a spin excitation continuum in the magnetically ordered state of Na_(2)BaCo(PO_(4))_(2),where free spinons are absent.This challenges the interpretation of such a continuum as a definitive signature of a quantum spin liquid in new material studies.展开更多
基金funded by the National Natural Science Foundations of China(Grant Nos.12034004 and 12174064)the Shanghai Municipal Science and Technology Major Project(Grant No.2019SHZDZX01)+2 种基金the Innovation Program for Quantum Science and Technology(Grant No.2024ZD0300104)supported by U.S.DOE BES DE-SC0012311the Robert A.Welch Foundation under Grant No.C-1839,respectively(P.D.)。
文摘One important issue in current condensed matter physics is the search of quantum spin liquid(QSL),an exotic magnetic state with strongly-fluctuating and highly-entangled spins down to zero temperature without static order.However,there is no consensus on the existence of a QSL state in any real material so far,due to inevitable disorder and intricate competing exchange interactions on frustrated spin lattices.Here we report systematic heat transport measurements on a honeycomb-lattice compound BaCo_(2)(AsO_(4))_(2),which manifests magnetic order in zero field.In a narrow in-plane field range after the magnetic order is nearly suppressed,in both perpendicular and parallel to the zigzag direction,a finite residual linear term of thermal conductivity is clearly observed,which is attributed to mobile fermionic excitations.In addition,the spin-phonon scattering rate exhibits a T-linear behavior when the order disappears.These observations suggest a partial QSL state with gapless spinon excitations in BaCo_(2)(AsO_(4))_(2),that emerges when a portion of the spins remains ordered,and vanishes as the spins become progressively polarized.
基金Supported by the National Key Research and Development Program of China under Grant Nos 2016YFA0300502,2016YFA0300503,2016YFA0300604,2016YF0300300 and 2016YFA0300802the National Natural Science Foundation of China under Grant Nos 11421092,11474330,11574359,11674406,11374346 and 11674375+3 种基金the National Basic Research Program of China(973 Program)under Grant No 2015CB921304the National Thousand-Young-Talents Program of Chinathe Strategic Priority Research Program(B) of the Chinese Academy of Sciences under Grant Nos XDB07020000,XDB07020200 and XDB07020300supported by DOE-BES under Grant No DE-FG02-04ER46148
文摘We report a new kagome quantum spin liquid candidate CuaZn（OH）6FBr, which does not experience any phase transition down to 50inK, more than three orders lower than the antiferromagnetic Curie-Weiss temperature （-200 K）. A clear gap opening at low temperature is observed in the uniform spin susceptibility obtained from 19F nuclear magnetic resonance measurements. We observe the characteristic magnetic field dependence of the gap as expected for fractionalized spin-1/2 spinon excitations. Our experimental results provide firm evidence for spin fractionalization in a topologically ordered spin system, resembling charge fraetionalization in the fractional quantum Hall state.
文摘安德森局域化是物理学中的一个基本现象,最初是安德森提出在晶体中电子受到杂质散射由于散射路径的相干导致电导完全消失,这完全来源于电子的波动特性,后来在其他各种波,如,光、微波、超声波,甚至是冷原子体系中都观察到安德森局域化现象。在晶体中,除电子外,还可能存在各种各样的磁激发准粒子,但是对于这些磁性准粒子的安德森局域化研究几乎没有。我们测量了苯甲酸铜Cu(C6H5COO)2·3H2O这个一维反铁磁海森堡链单晶的极低温比热和热导率,发现一直到50 m K的极低温,spinon磁性准粒子对比热都有一个恒定的线性贡献项Cs/T,但是其热导率的线性贡献项ks/T只保持不变到300 m K。在300m K以下,ks/T迅速减小,到100 m K以下就基本消失了。实验结果是spinon安德森局域化的一个较强的证据,为在凝聚态物理中研究安德森局域化现象开辟了一个新的窗口。
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).
基金supported by the National Key Research and Development Program of China(grant nos.2021YFA1400400,2022YFA1402204,and 2024YFA1408303)the National Natural Science Foundation of China(grant nos.12134020,12104255,12204223,12374124,and 12374146)+2 种基金the Open Fund of the China Spallation Neutron Source Songshan Lake Science City(grant no.KFKT2023A06)the Fundamental Research Funds for the Central Universities(grant no.226-2024-00068)the Guangdong Provincial Quantum Science Strategic Initiative(grant nos.GDZX2401006 and GDZX2401007).
文摘Spin excitation continua observed in neutron scattering studies are often considered to be strong evidence of quantum spin liquid formation.In a disorder-free magnetic compound with a quantum spin liquid ground state,the elementary excitation is no longer the conventional spin waves(magnons).Instead,the magnons fractionalize into spinons,producing a characteristic two-spinon continuum.However,it remained uncertain whether a clean,ordered antiferromagnet could exhibit a continuous spectrum similar to that of a quantum spin liquid.This paper presents evidence of a spin excitation continuum in the magnetically ordered state of Na_(2)BaCo(PO_(4))_(2),where free spinons are absent.This challenges the interpretation of such a continuum as a definitive signature of a quantum spin liquid in new material studies.
