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Host: Prof. Vadim Grinenko
Venue: TDLI Meeting Room N400
Tencent Meeting link: https://meeting.tencent.com/dm/eh2YI200rxuo Meeting ID: 116173702, no password
Abstract:
Superconductivity is a state of matter with many unique properties arising from broken gauge symmetry. Surprisingly some unusual superconductors also appear to break time reversal symmetry (TRSB). The origins of this are controversial. Here we examine the microscopic origin of an intrinsic Kerr effect due to chiral Copper pair states with non-zero angular momentum, in an analogue of the A phase of superfluid helium-3. We also predict small internal magnetic moments, related to the ‘angular momentum paradox’ of He-3. The 1.5K superconductor Sr2RuO4 is one of the best known examples of a TRSB superconductor. However the identification of this material as a chiral triplet superconductor analogous to He-3 is now known to be incorrect. We show that both Knight shift and uniaxial strain experiments imply a singlet d-wave state. The origin of TRSB in such a d-wave state is still not clear. I will discuss some of this controversial history and some of our ongoing work on this problem.
Biography:
James Annett is Professor of Physics at the University of Bristol in the UK. He studied physics at the University of Cambridge, obtaining his PhD in 1986 and then worked at the University of Illinois and Pennsylvania State University before moving to Bristol. His research concerns the nature and physical properties of materials. Specific interests include high temperature superconductors and other exotic superconducting materials. Related topics of research include superconducting devices which could have applications in quantum information or ‘spintronics’ devices. His book "Superconductivity, Superfluids and Condensates" is a widely used textbook for the subject.