Nernst effect in strange metals*

The strange-metal state is a crucial problem in condensed matter physics highlighted by its ubiquity in many correlated systems [1, 2]. Its understanding could provide important insight into high-T_c superconductivity and quantum criticality. However, with the Fermi liquid theory failing in strange metals, understanding the highly unconventional behaviors has been a long-standing challenge. Fundamental aspects of strange metals remain elusive, including the nature of their charge carriers. In this talk, I will report our recent effort in this direction using the Nernst effect as a sensitive probe to the entropy of charge carriers [3]. Specifically, we identified a strongly enhanced Nernst response in the strange-metal state in a two-dimensional superconductor 2M-WS₂ [4]. A large Nernst coefficient comparable to the vortex Nernst signal in superconducting cuprates, and its high sensitivity to carrier mobility, are found when the system enters the strange-metal state from the Fermi liquid state. The temperature and magnetic field dependence of the giant Nernst peak rule out the relevance of both Landau quasiparticles and superconductivity. Instead, the giant Nernst peak at the crossover indicates a dramatic change in carrier entropy when entering the strange-metal state. The presence of such an anomalous Nernst response is further confirmed in other iconic strange metals, suggesting its universality and places stringent experimental constraints on the mechanism of strange metals. 

 

[1] P. W. Phillips, N. Hussey, and P. Abbamonte, Stranger than metals, Science 377, 169 (2022).

[2] S. A. Hartnoll and A. P. Mackenzie, Colloquium: Planckian dissipation in metals. Rev. Mod. Phys. 94, 041002 (2022).

[3] K. Behnia and H. Aubin, Nernst effect in metals and superconductors: a review of concepts and experiments. Rep. Prog. Phys. 79, 046502 (2016)

[4] Y. Yang, et al., Anomalous enhancement of the Nernst effect at the crossover between a Fermi liquid and a strange metal, Nature Physics 19, 379 (2023).