Giant Nernst effect in the crossover between Fermi liquid and strange metal

TL;DR

This paper reports the discovery of a giant Nernst effect in a two-dimensional strange metal, revealing a fundamental change in carrier entropy and challenging existing theories of charge carriers in such states.

Contribution

It demonstrates a universal giant Nernst response in strange metals, providing new insights into their unconventional charge transport and entropy characteristics.

Findings

Giant Nernst coefficient observed in 2M-WS2 strange metal

Nernst response is highly sensitive to carrier mobility

Results challenge quasiparticle-based theories of strange metals

Abstract

The strange-metal state is a crucial problem in condensed matter physics highlighted by its ubiquity in almost all major correlated systems[1-7]. Its understanding could provide important insight into high-Tc superconductivity[2] and quantum criticality[8]. 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[1]. Here, we report the observation of a giant Nernst response in the strange-metal state in a two-dimensional superconductor 2M-WS2. A giant 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.