On the Detection of the Pairing Symmetry in Superconductors

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Abstract
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The pairing symmetry, mathematically defined as the representation of the unbroken symmetry group carried by the pairing order parameter, is considered as a classification and characterization of the broken symmetries in a superconductor. In this talk, we will introduce another concept, known as the projective symmetry group (PSG) of a superconductor. We will show that the PSG is closely related to the pairing symmetry, and in many cases imposes a strong constraint on the pairing symmetry. This constraint on pairing symmetry from PSG allows us to identify two new ways to detect pairing symmetry in a superconductor: (1) through new selection rules in optical/THz and Raman spectroscopy, (2) through the presence/absence of Majorana zero modes in vortex cores centered at high-symmetry locations of the crystal. I will illustrate the results using examples of superconductors w/ or w/o spin-orbit interactions.


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About the Speaker
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Yuan-Ming Lu obtained his Bachelor degree at Tsinghua University in 2007, and then finished his Ph.D. at Boston College in 2011. He did his postdoctoral research in University of California, Berkeley and Lawrence Berkeley National Laboratory during 2011-2014. He joined the faculty of Ohio State University in 2015 and is currently a professor of physics. His current research focuses on topological phases in strongly correlated systems. He is the recipient of NSF career award (2017) and the Outstanding Young Researcher Award of the International organization of Chinese Physicists and Astronomers (2020).