过渡金属合金的量子临界标度不变性
Quantum-critical scale invariance in a transition metal alloy
摘要：
在$T=0$的竞争阶段之间的量子力学波动诱导奇异的有限温度集体激发，这不是由标准的朗道费米液体框架描述。这些激发表现出异常的温度依赖性，或非费米液体行为，在量子临界点附近的输运和热力学性质，并经常密切相关的外观观察到的强相关系统，包括高- $T_c$铜酸盐和铁pnicide超导体的非常规库珀配对。然而，超导性的存在排除了直接接近量子临界点的可能性，并且使得难以评估量子临界涨落在形成反常的有限温度物理性质中的作用。在这里，我们报告的温度场标度不变性的非费米液体热力学，运输，和霍尔量在非超导铁磷属元素化物，Ba（Fe $_{1/3}$ Co $_{1/3}$ Ni $_{1/3}$）$_{2}$ As $_{2}$，表示量子临界在零温度和零施加磁场。除了线性的温度电阻率，强准粒子散射的标志性签名，我们发现的散射率服从温度和施加的磁场之间的普遍比例关系下降到最低的能量尺度。再加上接近零温度和零场极限的类空穴载流子的主导地位，尺度不变性，各向同性场响应，以及缺乏施加的压力敏感性表明了一个独特的量子临界系统，不会驱动配对不稳定性。
英文摘要：
Quantum-mechanical fluctuations between competing phases at $T=0$ induce exotic finite-temperature collective excitations that are not described by the standard Landau Fermi liquid framework. These excitations exhibit anomalous temperature dependences, or non-Fermi liquid behavior, in the transport and thermodynamic properties in the vicinity of a quantum critical point, and are often intimately linked to the appearance of unconventional Cooper pairing as observed in strongly correlated systems including the high-$T_c$ cuprate and iron pnictide superconductors. The presence of superconductivity, however, precludes direct access to the quantum critical point, and makes it difficult to assess the role of quantum-critical fluctuations in shaping anomalous finite-temperature physical properties. Here we report temperature-field scale invariance of non-Fermi liquid thermodynamic, transport, and Hall quantities in a non-superconducting iron-pnictide, Ba(Fe$_{1/3}$Co$_{1/3}$Ni$_{1/3}$)$_{2}$As$_{2}$, indicative of quantum criticality at zero temperature and zero applied magnetic field. Beyond a linear in temperature resistivity, the hallmark signature of strong quasiparticle scattering, we find the scattering rate that obeys a universal scaling relation between temperature and applied magnetic fields down to the lowest energy scales. Together with the dominance of hole-like carriers close to the zero-temperature and zero-field limits, the scale invariance, isotropic field response, and lack of applied pressure sensitivity suggests a unique quantum critical system that does not drive a pairing instability.
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