PHYSICS DISSERTATION DEFENSE: BaiYang Wang

Ph.D. Candidate:  BaiYang Wang

Research Advisor:  Harold Y. Hwang

Date: 05/24/2022
Time: 10:00am

Location: McCullough Building Room 335

Zoom Link:  https://stanford.zoom.us/j/95853964136

Zoom Password: email nickswan [at] stanford.edu (nickswan[at]stanford[dot]edu) for password.

 

Title: Investigation of Unconventional Superconductivity in Novel Geometry

Abstract: More than one century after the initial discovery of superconductivity in mercury, there remain entire classes of materials whose superconducting mechanisms have yet to be elucidated. One major avenue through which experimentalists contribute in this research has been finding new examples of unconventional superconductors. A recent trend in this materials search is to combine traditional material synthesis methods with novel sample manipulation techniques in pursuit of materials in novel geometries. For example, topotactic reduction has demonstrated impressive capabilities to modify oxygen stoichiometry and achieving extreme valence states of 3d transition metal ions in complex oxide systems. In this thesis, I will introduce the infinite-layer nickelates obtained using this method as a new family of 3d-transition-metal-based unconventional superconductors. I will show that this system is a local type-II superconductor with singlet pairing and nodal superconducting gap structure, whose upper critical field generically violates the Pauli limit. I will further identify the importance of rare earth 4f moments in shaping the superconductivity properties. Overall, I hope to show that this new system presents an additional source of experimental insight into unconventional superconductivity.