Pair density wave instability and Cooper pair insulators in gapped fermion systems
Abstract
By analyzing simple models of fermions in lattice potentials we argue that the zero-temperature pairing instability of any ideal band-insulator occurs at a finite momentum. The resulting supersolid state is known as "pair density wave". The pairing momentum at the onset of instability is generally incommensurate as a result of phase-space restrictions and relative strengths of interband and intraband pairing. However, commensurate pairing occurs in the strong-coupling limit and becomes a Cooper-channel analogue of the Halperin-Rice exciton condensation instability in indirect bandgap semiconductors. The exceptional sensitivity of incommensurate pairing to quantum fluctuations can lead to a strongly-correlated insulating regime and a non-BCS transition, even in the case of weak coupling as shown by an exact renormalization group analysis.
Cite
@article{arxiv.1007.2433,
title = {Pair density wave instability and Cooper pair insulators in gapped fermion systems},
author = {Predrag Nikolic and Anton A. Burkov and Arun Paramekanti},
journal= {arXiv preprint arXiv:1007.2433},
year = {2011}
}
Comments
Proceedings article for SCES 2010. To appear in Journal of Physics: Conference Series