Physics Department - Topological Superconductivity in Twisted Double-layer High-Tc Cuprates: Theory, Experimental Signatures and Applications
Abstract
Structures composed of two monolayer-thin d-wave superconductors with a twist angle close to 45° are predicted to form a robust, fully gapped topological superconducting phase with spontaneously broken time-reversal symmetry and protected chiral edge modes. In this talk I will briefly review the theory behind the topological phase and discuss recent experimental efforts to fabricate and probe twisted flakes of high-Tc cuprate Bi2Sr2CaCu2O8+δ. Signatures of d-wave symmetry and of spontaneous T-breaking are indeed visible in the device Josephson current response, as detected through a pronounced superconducting diode effect observed in samples near 45° twist but absent in untwisted samples. Time permitting, a potential application of this physics to an improved transmon qubit will also be discussed.
Marcel Franz is a Professor of Physics at The University of British Columbia and a Deputy Scientific Director of The Blusson Quantum Matter Institute. He obtained his PhD at The University of Rochester in 1994 and worked as a postdoctoral fellow and McMaster and Johns Hopkins universities before joining the faculty of The University of British Columbia in 2000. Franz is a leading expert in theories of topological quantum matter, unconventional superconductivity and strongly correlated electron systems. His group has made a number of significant advances in these fields including the recent prediction of high-temperature topological superconductivity in twisted bilayers of cuprate superconductors. Franz has received numerous awards and recognitions for his contributions including the A.P. Sloan Fellowship (2002), Killam Research Fellowship (2007), CAP Brockhouse Medal (2024) and has been elected Fellow of the APS (2014) and The Royal Society of Canada (2022).