Spectroscopic imaging of unconventional superconductors at ultra-low temperatures

自从1911年Onnes发现超导性以来，超导性一直引起科学界的兴趣。BCS超导理论描述了“传统”超导体[2]的特性，它描述了声子如何介导电子对之间的吸引相互作用，从而导致超导性。然而，许多材料都不属于传统超导体的范畴，在那里吸引人的电子相互作用不是声子介导的。这种材料，例如高温铜超导体，被称为非常规超导体。我们也可以将超导材料分为自旋单重态或自旋三重态（取决于每个电子对中两个电子的自旋）——这两个类别产生了不同的特性和潜在的应用。所有自旋三重态超导体都是非常规的，在量子超级计算中有令人兴奋的潜在应用，但尚未得到实验证实。扫描隧道显微镜（STM）可以通过测量状态密度和研究材料表面来研究超导性等特性[4-6]。该项目旨在研究超导分类不明确的材料（例如，自旋-单重态与自旋-单重态），如Sr2RuO4，以明确未来的潜在应用Van Delft， D. & Kes， P.超导性的发现。物理学今日63,38-43（2010年9月）Bardeen， J, Cooper， L. N.和Schrieffer， J. R.超导的微观理论。物理评论，106,162-164 （Apr. 1957）Devoret， M. H. & Schoelkopf， R. J.量子信息超导电路：展望。科学通报，2013,32 (2):444 - 444霍夫曼，j.e.等人。Bi2Sr2CaCu2O8-的成像准粒子干涉。科学297,1148-1151（2002年8月）Hanaguri， T.等。准粒子散射旋涡探测高tc铜的相干因子。科学323,923-926（2009年2月）克瑞塞尔，A.等。铜酸盐中扫描隧道准粒子干涉和杂质态的解释。物理评论快报114,217022（2015年5月）。

Superconductivity is a property that has intrigued the scientific community since it's discovery by Onnes in 1911 [1]. The BCS theory of superconductivity describes the properties of 'conventional' superconductors [2], which describes how phonons mediate an attractive interaction between pairs of electrons - which leads to superconductivity. Many materials, however, fall outside this realm of conventional superconductor, where the attractive electronic interaction is not phonon-mediated. Such materials, for example the high-temperature cuprate superconductors, are known as unconventional superconductors. We can also categorise superconducting materials as spin-singlet or spin-triplet (depending on the spins of the two electrons in each electron pair) - these two categories give rise to different characteristics and potential application. All spin-triplet superconductors would be unconventional and have exciting potential applications in quantum supercomputing, but are yet to be confirmed experimentally [3]. Scanning tunnelling microscopy (STM) can be used to investigate properties such as superconductivity through measuring the density of states and investigating the surfaces of materials [4-6]. This project aims to investigate materials with unclear superconductivity categorisation (e.g., spin-singlet vs. spin-singlet), such as Sr2RuO4, to provide clarity on future potential applications.[1] Van Delft, D. & Kes, P. The discovery of superconductivity. Physics Today 63, 38-43 (Sept.2010).[2] Bardeen, J., Cooper, L. N. & Schrieffer, J. R. Microscopic Theory of Superconductivity. Phys-ical Review 106, 162-164 (Apr. 1957).[3] Devoret, M. H. & Schoelkopf, R. J. Superconducting Circuits for Quantum Information: AnOutlook. Science 339, 1169-1174 (2013).[4] Hoffman, J. E. et al. Imaging Quasiparticle Interference in Bi2Sr2CaCu2O8- . Science 297,1148-1151 (Aug. 2002).[5] Hanaguri, T. et al. Coherence Factors in a High-TC Cuprate Probed by Quasi-Particle Scat-tering Off Vortices. Science 323, 923-926 (Feb. 2009).[6] Kreisel, A. et al. Interpretation of Scanning Tunneling Quasiparticle Interference and ImpurityStates in Cuprates. Physical Review Letters 114, 217022 (May 2015).