Shot noise in coupled electron-boson systems

Shot noise, a fundamental manifestation of current fluctuations, has recently emerged to serve as a powerful tool for probing strong correlations in quantum materials [1,2]. Traditionally used to determine the elementary charge carried by quasiparticles, shot noise now offers critical insights into the correlated electron systems [2]. In this work [3], we investigate quantum shot noise in correlated electron systems coupled to bosons by deriving a Boltzmann transport equation that incorporates the distribution functions of both degrees of freedom. We examine how electron-boson coupling influences the Fano factor—the ratio of the current noise to the average DC current—while allowing the bosons to go out of equilibrium. We identify the crucial role that the energy drag effect plays in determining the Fano factor. This includes the locking of the boson effective temperature to that of the fermions. We discuss the implications of our findings for shot noise experiments in the strange-metal regime of the quantum critical heavy fermion metal YbRh₂Si₂ [1].

*Supported by the AFOSR (FA9550-21-1-0356), NSF (DMR-2220603) and VBFF (N00014-23-1-2870)

[1] L. Y. Chen et al, Science 382, 907 (2023).

[2] Y. Wang et al., arXiv:2211.11735.

[3] Y. Wang et al., arXiv:2404.14515.