Events Calendar

24 Jan
Pitt/CMU Colloquium: Cyprian Lewandowski (CalTech)
Event Type

Lectures, Symposia, Etc.

Topic

Research

Target Audience

Undergraduate Students, Faculty, Graduate Students, Postdocs, Residents & Fellows

Tags

physics colloquia, CMU, Pitt-CMU

University Unit
Department of Physics and Astronomy
Subscribe
Google Calendar iCal Outlook

Pitt/CMU Colloquium: Cyprian Lewandowski (CalTech)

This is a past event.

Bose-Einstein condensation with a twist
Abstract: Superconductivity is a collective state in which many fermions pair up to give rise to a zero-resistance electron transport regime. The majority of superconductors are well described by a Bardeen-Cooper-Schrieffer (BCS) theory of superconductivity in which a weak momentum space attraction between fermions forms bound Cooper pairs separated in real space. When attraction becomes strong the Cooper pair size shrinks until it effectively forms a diatomic Bose molecule that can, in turn, undergo Bose-Einstein condensation (BEC). A solid-state realization of such a weak BCS to a strong BEC pairing crossover has, so far, eluded experimental observations. Recent electron transport experiments in twisted trilayer graphene [1] raise the possibility of such a transition revealing two distinct superconducting regimes. In this talk, I will discuss how these two regimes can be understood as a gate-tuned phase transition separating gapped BEC-like and gapless BCS-like superconducting phases. In particular, I will propose precise tunneling conductance signatures and demonstrate their consistency with the recent scanning tunneling microscopy measurements on twisted trilayer graphene [2].

[1] Park, J.M., Cao, Y., et al. Tunable strongly coupled superconductivity in magic-angle twisted trilayer graphene. Nature 590, 249–255 (2021)
[2] Kim, H., Choi, Y., et al. Spectroscopic Signatures of Strong Correlations and Unconventional Superconductivity in Twisted Trilayer Graphene. arXiv: 2109.12127

Dial-In Information

Virtual Event via Zoom.

Department members, see email for remote access information.
Non-department members, contact paugrad@pitt.edu for access or to be added to the weekly newsletter

Monday, January 24 at 3:35 p.m.

Virtual Event

Pitt/CMU Colloquium: Cyprian Lewandowski (CalTech)

Bose-Einstein condensation with a twist
Abstract: Superconductivity is a collective state in which many fermions pair up to give rise to a zero-resistance electron transport regime. The majority of superconductors are well described by a Bardeen-Cooper-Schrieffer (BCS) theory of superconductivity in which a weak momentum space attraction between fermions forms bound Cooper pairs separated in real space. When attraction becomes strong the Cooper pair size shrinks until it effectively forms a diatomic Bose molecule that can, in turn, undergo Bose-Einstein condensation (BEC). A solid-state realization of such a weak BCS to a strong BEC pairing crossover has, so far, eluded experimental observations. Recent electron transport experiments in twisted trilayer graphene [1] raise the possibility of such a transition revealing two distinct superconducting regimes. In this talk, I will discuss how these two regimes can be understood as a gate-tuned phase transition separating gapped BEC-like and gapless BCS-like superconducting phases. In particular, I will propose precise tunneling conductance signatures and demonstrate their consistency with the recent scanning tunneling microscopy measurements on twisted trilayer graphene [2].

[1] Park, J.M., Cao, Y., et al. Tunable strongly coupled superconductivity in magic-angle twisted trilayer graphene. Nature 590, 249–255 (2021)
[2] Kim, H., Choi, Y., et al. Spectroscopic Signatures of Strong Correlations and Unconventional Superconductivity in Twisted Trilayer Graphene. arXiv: 2109.12127

Dial-In Information

Virtual Event via Zoom.

Department members, see email for remote access information.
Non-department members, contact paugrad@pitt.edu for access or to be added to the weekly newsletter

Monday, January 24 at 3:35 p.m.

Virtual Event

Topic

Research

Powered by the Localist Community Events Calendar ©