Neutron Spectroscopy Evidence for a Possible Magnetic-Field-Induced Gapless Quantum-Spin-Liquid Phase in a Kitaev Material α-RuCl_3
Neutron Spectroscopy Evidence for a Possible Magnetic-Field-Induced Gapless Quantum-Spin-Liquid Phase in a Kitaev Material α-RuCl_3
复制标题
Kitaev 材料 α-RuCl_3 中可能存在磁场感应无间隙量子自旋液相的中子能谱证据
DOI：
10.1088/0256-307x/39/5/057501
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发表时间：
2022
影响因子：
3.5
通讯作者：
Wen Jinsheng
中科院分区：
文献类型：
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作者：
Zhao Xiaoxue;Ran Kejing;Wang Jinghui;Bao Song;Shangguan Yanyan;Huang Zhentao;Liao Junbo;Zhang Bo;Cheng Shufan;Xu Hao;Wang Wei;Dong Zhaoyang;Meng Siqin;Lu Zhilun;Yano Shinichiro;Yu Shunli;Li Jianxin;Wen Jinsheng
α-RuCl_3是Kitaev量子自旋液体（QSL）的最有希望的候选者之一，受到了广泛的关注。然而，它的基态具有长程锯齿形的磁序，这阻碍了QSL相的形成。然而，这种磁序是脆弱的，可以通过施加外费尔德而被完全抑制。本文研究了α-RuCl_3在面内费尔德下的磁激发演化，通过对高质量单晶进行非弹性中子散射测量，发现在零费尔德下，M点附近存在自旋波激发，而在Γ点附近存在连续谱，它们分别与Kitaev QSL态的Z字形磁序和分数激发有关.通过增加费尔德，自旋波激发逐渐让位于连续激发，在临界费尔德μ_0H_c = 7.5 T附近，前者消失，只剩下后者，进一步增加费尔德强度，在Γ点附近的激发变得更强，通过跟踪Γ点附近激发的差距演化，我们能够建立由三个有趣相组成的相图，结果表明，面内费尔德可以驱动α-RuCl_3在临界费尔德附近进入一个长期以来一直寻找的QSL态.
As one of the most promising Kitaev quantum-spin-liquid (QSL) candidates,α-RuCl_3 has received a great deal of attention.However,its ground state exhibits a long-range zigzag magnetic order,which defes the QSL phase.Nevertheless,the magnetic order is fragile and can be completely suppressed by applying an external magnetic feld.Here,we explore the evolution of magnetic excitations of α-RuCl_3 under an in-plane magnetic feld,by carrying out inelastic neutron scattering measurements on high-quality single crystals.Under zero feld,there exist spin-wave excitations near the M point and a continuum near the Γ point,which are believed to be associated with the zigzag magnetic order and fractional excitations of the Kitaev QSL state,respectively.By increasing the magnetic feld,the spin-wave excitations gradually give way to the continuous excitations.On the verge of the critical feld µ_0H_c = 7.5 T,the former ones vanish and only the latter ones are left,indicating the emergence of a pure QSL state.By further increasing the feld strength,the excitations near the Γ point become more intense.By following the gap evolution of the excitations near the Γ point,we are able to establish a phase diagram composed of three interesting phases,including a gapped zigzag order phase at low felds,possibly gapless QSL phase near µ_0H_c,and gapped partially polarized phase at high felds.These results demonstrate that an in-plane magnetic feld can drive α-RuCl_3 into a long-sought QSL state near the critical feld.