Nonequilibrium noise as a probe of pair-tunneling transport in the BCS-BEC crossover

Hiroyuki Tajima; Daigo Oue; Mamoru Matsuo; Takeo Kato

doi:10.1093/pnasnexus/pgad045

Nonequilibrium noise as a probe of pair-tunneling transport in the BCS-BEC crossover

PNAS Nexus. 2023 Feb 9;2(3):pgad045. doi: 10.1093/pnasnexus/pgad045. eCollection 2023 Mar.

Authors

Hiroyuki Tajima¹, Daigo Oue^{2

3

4}, Mamoru Matsuo^{2

5

6

7}, Takeo Kato⁸

Affiliations

¹ Department of Physics, Graduate School of Science, The University of Tokyo, Tokyo 113-0033, Japan.
² Kavli Institute for Theoretical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China.
³ Instituto Superior Técnico, University of Lisbon, Lisboa 1049-001, Portugal.
⁴ The Blackett Laboratory, Department of Physics, Imperial College London, Prince Consort Road, Kensington, London SW7 2AZ, UK.
⁵ CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100190, China.
⁶ Advanced Science Research Center, Japan Atomic Energy Agency, Tokai 319-1195, Japan.
⁷ RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama 351-0198, Japan.
⁸ The Institute for Solid State Physics, The University of Tokyo, Kashiwa 277-8581, Japan.

Abstract

The detection of elementary carriers in transport phenomena is one of the most important keys to understand nontrivial properties of strongly correlated quantum matter. Here, we propose a method to identify the tunneling current carrier in strongly interacting fermions from nonequilibrium noise in the Bardeen-Cooper-Schrieffer to Bose-Einstein condensate crossover. The noise-to-current ratio, the Fano factor, can be a crucial probe for the current carrier. Bringing strongly correlated fermions into contact with a dilute reservoir produces a tunneling current in between. The associated Fano factor increases from one to two as the interaction becomes stronger, reflecting the fact that the dominant conduction channel changes from the quasiparticle tunneling to the pair tunneling.

Keywords: BCS–BEC crossover; nonequilibrium noise; strongly interacting fermions; transport.