横向热电响应作为准粒子存在性的探针
Transverse Thermoelectric Response as a Probe for Existence of Quasiparticles
摘要：
具有反射对称性的各向异性相互作用系统的霍尔电导率服从sigma_{xy} = - sigma_{yx}。相反，我们表明，横向热电Peltier系数之间的类似关系，alpha_{xy} = - alpha_{yx}，一般不成立，在同一系统。这一事实可以追溯到相互作用的热流算子和热电响应函数的混合性质的贡献。然而，值得注意的是，低温下准粒子的出现似乎迫使alpha_{xy} = - alpha_{yx}。这表明，准粒子自由基态（所谓的非费米液体）可以通过检查之间的关系alpha_{xy}和alpha_{yx}在反射对称性和微观各向异性的存在下检测。这些结论是基于以下结果：（i）弹性散射的非相互作用粒子的珀耳帖系数之间的关系是准确的;（ii）它保持近似玻尔兹曼理论的相互作用粒子时，弹性散射占主导地位的非弹性过程。在无序的费米液体中，后者导致的偏差以T^3的形式消失。(iii)我们计算了热电响应的弱耦合自旋能隙的Luttinger液体的模型，并获得了强烈的非对角分量之间的反对称性的破坏。我们还发现，在这个模型中的能斯特信号被增强的相互作用，并可以改变的磁场和温度的函数的符号。
英文摘要：
The electrical Hall conductivities of any anisotropic interacting system with reflection symmetry obey sigma_{xy} = - sigma_{yx}. In contrast, we show that the analogous relation between the transverse thermoelectric Peltier coefficients, alpha_{xy}= - alpha_{yx}, does not generally hold in the same system. This fact may be traced to interaction contributions to the heat current operator and the mixed nature of the thermoelectric response functions. Remarkably, however, it appears that emergence of quasiparticles at low temperatures forces alpha_{xy} = - alpha_{yx}. This suggests that quasiparticle-free groundstates (so-called non-Fermi liquids) may be detected by examining the relationship between alpha_{xy} and alpha_{yx} in the presence of reflection symmetry and microscopic anisotropy. These conclusions are based on the following results: (i) The relation between the Peltier coefficients is exact for elastically scattered noninteracting particles; (ii) It holds approximately within Boltzmann theory for interacting particles when elastic scattering dominates over inelastic processes. In a disordered Fermi liquid the latter lead to deviations that vanish as T^3. (iii) We calculate the thermoelectric response in a model of weakly-coupled spin-gapped Luttinger liquids and obtain strong breakdown of antisymmetry between the off-diagonal components of alpha. We also find that the Nernst signal in this model is enhanced by interactions and can change sign as function of magnetic field and temperature.
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