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THE SUPERCONDUCTING ENERGY GAP

机译：超导能量缺口

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The superconducting gap can be defined as the energy difference between the ground state of the superconductor and the energy of the lowest quasiparticle excitation [II. There were early hints that such a gap existed but the first experimental evidence for a gap came from the temperature dependence of the specific heat below the transition temperature T as measured by Corak et al. [2]. It was found that the electronic specific heat was given by Cec.7T ce-1.5 TcIT where y is the normal state electronic specific heat coefficient and T the superconducting transition temperature. The first spectroscopic measurement of the energy gap was carried out with microwaves by Biondi et a1131 on aluminum and far infrared techniques by Glover et al [4] on lead. At the same time, the microscopic theory of superconductivity, the BCS theory, was announced by Bardeen, Cooper and Schrieffer [5] who predicted the value of the ratio of the superconducting gap to the transition temperature to be 1.76 which is in excellent agreement with the spectroscopic measurements. This was one of the earliest triumphs of the theory. It should be noted that this value of the gap is from the weak coupling limit of the theory and applies to materials with low Te's such as aluminum. For conventional superconductors, tunnelling spectroscopy [6] has been a popular tool for gap measurement but for the new high temperature superconductors, with their larger gaps, infrared and photoemission spectroscopies have played an increasingly important role.
机译：超导间隙可以定义为超导体基态与最低准粒子激发能之间的能量差[II。]。早期有迹象表明存在这种间隙，但最早的实验证据是由比拉克温度低于转变温度T的比热对温度的依赖性，如Corak等人所测量。 [2]。发现电子比热由Cec.7T ce-1.5 TcIT给出，其中y为常态电子比热系数，T为超导转变温度。能谱的第一次光谱测量是由Biondi等人在铝上用微波进行的，而远红外技术是由Glover等人在铅上进行的远红外技术[4]进行的。同时，Bardeen，Cooper和Schrieffer [5]宣布了超导微观理论BCS理论，他们预测超导间隙与转变温度之比的值为1.76，这与光谱测量。这是该理论的最早胜利之一。应该注意的是，该间隙值是从理论上的弱耦合极限得出的，并且适用于诸如铝的具有低Te的材料。对于常规的超导体，隧道光谱[6]已成为一种用于间隙测量的流行工具，但是对于新型的高温超导体，由于其间隙较大，红外光谱和光发射光谱学起着越来越重要的作用。

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