量子涨落与过掺杂铜氧化物超导薄膜中的反常两段标度

Quantum Fluctuations and the Anomalous Two-Class Scaling in the Overdoped Cuprate Films

通过引入虚时间变量,将绝对零度附近的金兹堡−朗道方程推广为一个精确的相对论方程。基于该方程所建立的虚时量子场论,描述过掺杂铜氧化物超导材料在绝对零度附近的量子临界现象。利用虚时量子场论框架,理论推导出在La_(2-x)Sr_(x)CuO_(4)超导薄膜的过掺杂区域所观测到的零温超流相位刚度与相变温度之间的反常两段标度,且理论计算结果与实验测量值吻合良好。该研究推测:处于绝对零度附近的过掺杂超导薄膜中,零温相干长度与相变温度也服从一个两段标度,理论得到的两个临界指数1和1.34有待实验的检验。

By introducing the imaginary time,we show that Gor’kov’s Ginzburg-Landau equation at zero temperature can be extended to an exact relativistic form.Based on this equation,we propose a quantum field theory with the imaginary time,which is intended to describe the quantum critical phenomena in the zero-temperature overdoped cuprate.By using such a quantum field theory,we show that the anomalous two-class scaling between the transition temperature T_(c) and zero-temperature superfluid phase stiffnessρ_(s)(0) observed in the overdoped side of single-crystal La_(2-x)Sr_(x)CuO_(4) films can be derived exactly.In this paper,we further theoretically show that,for 2-dimensional overdoped cuprate films,the transition temperature T_(c) and the zero-temperature coherence lengthζ(0)will obey a two-class scaling as well.When the transition temperature T_(c) is less than a characteristic temperature scaleT_(Q),the transition temperature T_(c) and the zero-temperature coherence lengthζ(0)obeys the scalingζ(0)∝T_(c)^(-1.34),which is a quantum critical behavior.Nevertheless,when the transition temperature is larger than another characteristic temperature scale T_(M),the scaling relationship will yieldζ(0)∝T_(c)^(-1),which is a mean-field behavior.