Tunneling Measurements of the Cuprate Superconductors
Tunneling Measurements of the Cuprate Superconductors
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DOI：
10.1007/978-0-387-68734-6_2
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发表时间：
2007
期刊：
影响因子：
3.4
通讯作者：
J. Kirtley;F. Tafuri
中科院分区：
文献类型：
--
作者：
J. Kirtley;F. Tafuri
在非常简要地描述了从传统超导体的隧穿测量中所学到的东西之后，我们概述了与铜酸盐相关的一般概念。这些包括所使用的结结构的类型，由于从点接触到隧穿制度的可变结透明度的影响，邻近效应，Andreev散射，非常规配对对称性，以及可能的时间反转对称性破坏。本文介绍了在高温铜氧化物超导体中获得隧道结的各种方法。我们描述了铜氧化物超导体的非常规配对对称性如何导致π环和0-π结，以及这些效应如何被用来确定铜氧化物中的差距主要具有dx 2 − y2配对对称性。然后我们转向隧道光谱学。超导带隙、赝带隙和零偏压电导峰是密切相关的。超导带隙和零偏压电导峰可以理解为具有dx 2 − y2配对对称性的电极之间通过低和高跨导势垒的输运。赝能隙代表的是与超导性竞争的有序还是预形成的库珀对，这是有争议的。类似地，在隧道光谱测量中有许多时间反演对称性破缺的迹象，但在π环和0-π结的测量中没有。原子分辨扫描隧道光谱中的电导率调制当然可以由准粒子干涉效应引起，但也有非色散电导率调制的证据，预计从条纹模型。我们描述了强耦合效应涉及声子和磁振子相互作用的准粒子在超导态的隧穿证据。
After a very brief description of what has been learned from tunneling measurements in conventional superconductors, we provide an overview of general concepts relevant to the cuprates. These include the types of junction structures used, effects due to variable junction transparency from the point contact to the tunneling regimes, proximity effects, Andreev scattering, unconventional pairing symmetry, and possible broken time reversal symmetry. We describe the various methods used for obtaining tunneling junctions in the high-temperature cuprate superconductors. We describe how the unconventional pairing symmetry of the cuprate superconductors leads to π-rings and 0–π-junctions, and how these effects have been used to determine that the gap in the cuprates has predominantly dx2− y2 pairing symmetry. We then turn to tunneling spectroscopy. The superconducting gap, the pseudogap, and zero bias conductance peaks are closely interrelated. The superconducting gap and zero bias conductance peaks can be understood in terms of transport between electrodes with dx2− y2 pairing symmetry through low and high transmissivity barriers. It is controversial whether the pseudogap represents an order competing with superconductivity or preformed Cooper pairs. Similarly, there are many indications of broken time reversal symmetry in tunneling spectroscopy measurements, but not in measurements of π-ring and 0–π-junctions. Conductivity modulations in atomically resolved scanning tunneling spectroscopy certainly can arise from quasiparticle interference effects, but there is also evidence for nondispersive conductivity modulations, expected from stripe models. We describe tunneling evidence for strong coupling effects involving phonon and magnon interactions with the quasiparticles in the superconducting state.