【摘要】 高温超导体赝隙态与超导态之间的关系一直是研究的焦点.交流电导和能斯特(Nernst)效应测量相继探测到超导转变温度Tc0以上温区一定范围内存在磁通涡旋激发,利用力矩技术的磁化率测量则探测到超导涨落引起的弱抗磁性.这些发现都支持了高温超导体赝隙相中存在有限的超导序参量振幅和强烈的位相涨落的图像,说明Tc0处的相变是由库珀对之间长程位相关联的消失所驱动的.文章首先简短地介绍高温超导体的电子态相图和赝隙态,以及能斯特效应的原理和测量方法,然后对能斯特效应的测量结果作一评述性介绍,还讨论了相关的理论模型.更多还原

【Abstract】 The relationship between pseudogap and superconducting states of high-T_C superconductors has been a focus of interest for a long time. Measurements of the AC conductivity and the Nernst effect have detected vortex-like excitations in a certain temperature range above the superconducting transition temperature T_C. Meanwhile, the measurement of susceptibility by the torque technique has also detected weak diamagnetization induced by superconducting fluctuations above T_C. These findings strongly support the idea that the pseudogap phase is characterized by a finite pairing amplitude with strong phase fluctuations, and imply that the phase transition at T_C is driven by the loss of long-range phase coherence. We first briefly introduce the electronic phase diagram and pseuodgap state of high-T_C superconductors, the principle of the Nernst effect, and the measurement technique. Then the results of the Nernst effect for different high-T_C superconductors are reviewed and discussed. Related theoretical models are also discussed.更多还原