Northwestern Events Calendar

Nov
8
2019

Special CMP Seminar: Professor Mohit Randeria: Bounds on the Superconducting Transition Temperature: Applications to Twisted Bilayer Graphene, FeSe/STO and Cold Atoms

When: Friday, November 8, 2019
2:00 PM - 3:00 PM Central

Where: Technological Institute, F160, 2145 Sheridan Road, Evanston, IL 60208 map it

Audience: Faculty/Staff - Student - Public - Post Docs/Docs - Graduate Students

Contact: Cristian Pennington  

Group: Physics and Astronomy Condensed Matter Physics Seminars

Category: Academic

Description:

Understanding limits on the superconducting transition temperature Tc is a problem of fundamental importance. I will discuss rigorous upper bounds on the superfluid phase stiffness for interacting, multi-band systems, valid in any dimension. This in turn leads to upper bounds [1] on Tc in 2D that hold irrespective of pairing mechanism, interaction strength, or order-parameter symmetry, so long as one has a BKT transition. Our bounds are particularly useful for the strongly correlated regime of low-density, narrow band systems, where mean-field theory fails. For a simple parabolic band in 2D with Fermi energy Ef, we find that Tc can never exceed Ef/8, an exact result that has direct implications for the 2D BCS-BEC crossover in ultracold Fermi gases. I will then discuss the application of our multi-band bounds to monolayer FeSe/STO and to magic-angle twisted bilayer graphene, where we find very interesting results for Tc constrained by the band structure. Finally, I will discuss the question of deriving rigorous upper bounds on Tc in 3D.

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

Professor Mohit Randeria, Ohio State University

Host: Anupam Garg

Keywords: Physics, Astronomy, Condensed Matter

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