This paper aims to clarify the nature of a surprising ordered phase recently reported in biased Bernal bilayer graphene that occurs at the phase boundary between the isospin-polarized and unpolarized phases. Strong nonlinearity of transport at abnormally small currents, with dI/dV vs. I sharply rising and then falling back, is typical for a charge/spin-density-wave state (CDW or SDW) sliding transport. Here, however, it is observed at an isospin-order phase boundary, prompting a question about the CDW/SDW mechanism and its relation to the quantum critical point. We argue that the observed phase diagram cannot be understood within a standard weak-coupling picture. Rather, it points to a mechanism that relies on an effective interaction enhancement at a quantum critical point. We develop a detailed strong-coupling framework accounting for the soft collective modes that explain these observations.
@article{arxiv.2404.18073,
title = {Charge and spin density wave orders in field-biased Bernal bilayer graphene},
author = {Zhiyu Dong and Patrick A. Lee and Leonid Levitov},
journal= {arXiv preprint arXiv:2404.18073},
year = {2024}
}