Quantum critical behavior in the asymptotic limit of high disorder in the medium entropy alloy NiCoCr0.8
Quantum critical behavior in the asymptotic limit of high disorder in the medium entropy alloy NiCoCr0.8
复制标题
DOI：
10.1038/s41535-017-0042-7
复制
发表时间：
2017-06-29
影响因子：
5.7
通讯作者：
McGuire, Michael A.
中科院分区：
文献类型：
--
作者：
Sales, Brian C.;Jin, Ke;McGuire, Michael A.
物质在量子临界点附近的行为是物理学研究中最令人兴奋和最具挑战性的领域之一。诸如高温超导等紧急现象与接近量子临界点有关。虽然在了解一些低维磁绝缘体的量子临界行为方面取得了重大进展，但在金属体系中的情况却不太清楚。在这里，我们证明了NiCoCrx单晶合金是研究金属环境中量子临界点物理的卓越模型系统。对于x近似于0.8的NiCoCrx合金，通过低温磁化和热容测量，实验确定了与铁磁量子临界点相关的临界指数。所有五个指数(gamma(T)近似于1/2，beta(T)近似于1，delta近似于3/2，nu z（m)近似于2，(alpha) / barT近似于0）在高无序的渐近极限下与Belitz-Kirkpatrick-Vojta理论的预测显著一致。利用这些关键指数，证明了在没有可调参数的情况下，磁化数据具有良好的缩放性。我们还发现磁性格吕尼森参数的散度与铁磁量子临界点一致。因此，这项工作表明，熵稳定的浓缩固溶体代表了一个独特的平台来研究高度可调材料的量子临界行为。
The behavior of matter near a quantum critical point is one of the most exciting and challenging areas of physics research. Emergent phenomena such as high-temperature superconductivity are linked to the proximity to a quantum critical point. Although significant progress has been made in understanding quantum critical behavior in some low dimensional magnetic insulators, the situation in metallic systems is much less clear. Here, we demonstrate that NiCoCrx single crystal alloys are remarkable model systems for investigating quantum critical point physics in a metallic environment. For NiCoCrx alloys with x approximate to 0.8, the critical exponents associated with a ferromagnetic quantum critical point are experimentally determined from low temperature magnetization and heat capacity measurements. All of the five exponents (gamma(T) approximate to 1/2, beta(T) approximate to 1, delta approximate to 3/2, nu z(m) approximate to 2, (alpha) over barT approximate to 0) are in remarkable agreement with predictions of Belitz-Kirkpatrick-Vojta theory in the asymptotic limit of high disorder. Using these critical exponents, excellent scaling of the magnetization data is demonstrated with no adjustable parameters. We also find a divergence of the magnetic Gruneisen parameter, consistent with a ferromagnetic quantum critical point. This work therefore demonstrates that entropy stabilized concentrated solid solutions represent a unique platform to study quantum critical behavior in a highly tunable class of materials.