Ohio State is in the process of revising websites and program materials to accurately reflect compliance with the law. While this work occurs, language referencing protected class status or other activities prohibited by Ohio Senate Bill 1 may still appear in some places. However, all programs and activities are being administered in compliance with federal and state law.

Colloquium - Mohit Randeria (Ohio State University) - Are there bounds on the superconducting transition temperature?

 Professor Mohit Randeria

Are there bounds on the superconducting transition temperature?

Dr. Mohit Randeria
Ohio State University

Watch the recording

Faculty Host: Chris Hammel

 Professor Mohit Randeria

Abstract: Understanding limits on the superconducting transition temperature Tc is a question of fundamental and practical importance. I will begin by describing developments in quantum materials and ultracold atoms that challenge conventional wisdom on what controls Tc. I will then describe exact upper bounds [1] on Tc for two dimensional (2D) systems, valid for any pairing mechanism or strength. The 2D bound takes a particularly simple form for parabolic dispersion -- Tc cannot exceed one-eighth the Fermi temperature – which has been realized in recent experiments [2,3].  I will next describe results for multi-band systems with complex band structures and discuss applications to 2D superconducting materials including twisted bilayer graphene. I will briefly describe progress on topological flat bands, where the Tc bound [4] involves the “quantum geometry” of electronic wave functions. I will conclude by describing the challenges in deriving bounds on Tc in 3D, which remains an open problem.

 

[1] T. Hazra, N. Verma, M. Randeria, Phys. Rev. X 9, 031049 (2019)

[2] Y. Nakagawa et al., Science 372, 190 (2021)

[3] M. Randeria, Science 372,132 (2021)

[4] N. Verma, T. Hazra, M. Randeria, Proc. Nat. Acad. Sci. 118, e2106744118 (2021)