ABSTRACT
Unconventional superconductivity can be understood as a macroscopic quantum phenomenon in which symmetries beyond the U(1) symmetry is broken, which is in turn induced by electron pairing as in the conventional superconductors. A hallmark for the unconventional superconductivity is the non-s-wave orbital part of the superconducting order parameter (OP) or macroscopic wave function (WF). Sr2RuO4 and UTe2, for which the non-s-wave pairing is quite well established, are two promising candidates for the more exotic odd-party, spin-triplet superconductivity. While Sr2RuO4 is the first and only layered perovskite superconductor with the normal electronic states on the Fermi surface formed primarily from 4d orbitals, UTe2 is a (recently discovered) heavy fermion superconductor possessing a highly anisotropic Fermi surface with electronic states dominated by strongly correlated 5f electrons of U. In this talk I will give a brief overview of the experimental work on Sr2RuO4 and UTe2 and discuss our own work on the phase-sensitive determination of the symmetry properties of the OP of these two superconductors, including the recent debate on the implications of the NMR Knight shift measurements on Sr2RuO4.
BIOGRAPHY
Ying Liu, professor of physics at Pennsylvania State University, received his BS degree from Peking University in 1982, MS degree from Institute of Physics, CAS in 1984, and PhD degree from University of Minnesota in 1991, and. Prof. Liu joined the faculty of Penn State Physics in 1994 after performing postdoctoral research at University of Colorado, Boulder, becoming tenured full professor in 2005. His research is focused on the experimental studies of low-dimensional and unconventional superconductors. He also worked on graphene, topological insulators, 2D crystals, as well as strongly correlated electronic systems. Professor Liu received an NSF Career Award in 1997 and was selected as a fellow of American Physical Society in 2006. He received an Outstanding Young Investigator (Type B) award from NSFC in 2007 and was a Chang Jiang Lecturer Professor (part-time) at Zhejiang University (2007-2010) and a Hongwen Professor (part-time) at Shanghai Jiao Tong University (2012-2019).
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