Visualizing Exotic Density Waves and Boundary States in the Triplet superconductor in UTe2
Date : October 4, 2023 16:00 ~
Speaker : Vidya Madhaven (University of Illionois Urbana-Champaign)
Professor : Prof. Dohun Kim, Prof. Sunghoon Jung
Location : 56동105호
Topological superconductors represent a fundamentally new phase of matter. Similar to topological insulators, the non-trivial topological characteristics of a topological superconductor dictate the presence of a topological edge states which live inside and span the superconducting gap. The intense interest in topological superconductivity stems from the fact that these boundary modes are predicted to have all the characteristics of the long-sought after Majorana Fermions. Theoretical studies have shown that a natural platform for realizing topological superconductivity is a triplet superconductor which is a condensate of electron pairs with spin-1 and an odd-parity wavefunction. Triplet pairing is however rare in solid state systems with the best-known example being the superfluid 3He-A phase. Motivated by the possibility of realizing Majorana fermions, over the last few decades, there has been an intense search for potential spin-triplet superconductors in solid-state systems. I will start the talk with a discussion of an intuitive way to understand why triplet superconductors are natural candidates to realize Majorana excitations. I will then present scanning tunneling microscopy (STM) data on the newly discovered heavy fermion superconductor, UTe2 with a TSC of 1.6 K. STM spectroscopy at step edges show signatures of in-gap states with an intriguing chiral signature. I will discuss the potential origin of these edge states. In the second part of the talk, I will discuss our STM studies that show the existence of a new type of charge density wave which is sensitive to magnetic fields. I will then show how the CDW state melts in a magnetic field by the creation of pairs of CDW `vortices’ with opposite phase winding and discuss the possibility that the CDW arises form a new kind of superconducting state which hosts a novel density wave made up of triplet cooper pairs.