Thermodynamic Perspective on Field-Induced Behavior of α-RuCl3
Thermodynamic Perspective on Field-Induced Behavior of α-RuCl3
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DOI：
10.1103/physrevlett.125.097203
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发表时间：
2020-08-25
影响因子：
8.6
通讯作者：
Gegenwart, P.
中科院分区：
文献类型：
--
作者：
Bachus, S.;Kaib, D. A. S.;Gegenwart, P.
对 Kitaev 候选材料 α-RuCl3 的磁 GrUneisen 参数 (Gamma(B)) 和比热的测量用于获取高达 12 T 和低至 1 K 的熵的面内场和温度依赖性。在磁有序区域的边界之外没有检测到与相变相对应的特征，但仅在 Gamma(B) 中检测到肩状异常，涉及很小的熵增量 为 10(-5) R log 2。这些观察结果对所谓的量子自旋液体和 α-RuCl3 场极化态之间是否存在相变提出了质疑。我们从理论上证明，在低温下，Gamma(B) 对带隙相内最低激发的交叉敏感，并将测量到的肩状异常识别为这种起源。精确的对角化计算表明，肩状异常可以在扩展的 Kitaev 模型中重现，该模型可以在有限场中接近附加相，而无需进入它。我们讨论这种接近性在其他测量中的表现。
Measurements of the magnetic GrUneisen parameter (Gamma(B)) and specific heat on the Kitaev material candidate alpha-RuCl3 are used to access in-plane field and temperature dependence of the entropy up to 12 T and down to 1 K. No signatures corresponding to phase transitions are detected beyond the boundary of the magnetically ordered region, but only a shoulderlike anomaly in Gamma(B), involving an entropy increment as small as 10(-5) R log 2. These observations put into question the presence of a phase transition between the purported quantum spin liquid and the field-polarized state of alpha-RuCl3. We show theoretically that at low temperatures Gamma(B) is sensitive to crossings in the lowest excitations within gapped phases, and identify the measured shoulderlike anomaly as being of such origin. Exact diagonalization calculations demonstrate that the shoulderlike anomaly can be reproduced in extended Kitaev models that gain proximity to an additional phase at finite field without entering it. We discuss manifestations of this proximity in other measurements.