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arXiv 0910.1966cond-mat.str-elcond-mat.supr-con
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从赝能隙相的d密度波理论看铜氧化物超导体中的准粒子能斯特效应

Quasiparticle Nernst effect in the cuprate superconductors from the d-density wave theory of the pseudogap phase

Chuanwei Zhang, Sumanta Tewari, Sudip Chakravarty

摘要:

在赝能隙相的d密度波模型下,研究了铜氧化物高温超导体欠掺杂区的能斯特效应。通过分析和数值参数的组合,我们表明,有一个强大的低温正峰(即,当DDW状态是双极性时,即,当对称性破缺支持电子和空穴类准粒子在激发光谱中共存时,电子袋在低温下占主导地位。相反,如果潜在状态是非双极的,即,当它只支持一种准粒子时更一般地,在双极状态下,能斯特系数的符号可以是正的或负的,这分别取决于低温热电输运中电子或空穴袋的主导性。通过模拟赝能隙相的掺杂依赖DDW序参量与费米表面拓扑结构,支持空穴和电子口袋,并假设能量无关的传输散射时间,我们分析了能斯特效应的演变与掺杂浓度在低温下的铜酸盐相图。

英文摘要:

We consider the Nernst effect in the underdoped regime of the cuprate high temperature superconductors within the d-density wave (DDW) model of the pseudogap phase. By a combination of analytical and numerical arguments, we show that there is a robust low-temperature positive peak (i.e., maximum) in the temperature dependence of the Nernst coefficient when the DDW state is ambipolar, i.e., when the broken symmetry supports the coexistence of both electron- and hole-like quasiparticles in the excitation spectrum, and the electron pocket dominates at the low temperatures. In contrast, the Nernst coefficient is negative and there is no such positive peak if the underlying state is non-ambipolar, i.e., when it supports only one type of quasiparticles. More generally, in the ambipolar state, the sign of the Nernst coefficient can be positive or negative depending on the dominance of the electron or hole pockets, respectively, in the low temperature thermoelectric transport. By modeling the pseudogap phase by a doping-dependent DDW order parameter with a Fermi surface topology that supports both hole and electron pockets, and assuming energy-independent transport scattering times, we analyze the evolution of the Nernst effect with doping concentration at low temperatures in the cuprate phase diagram.

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