Strange Half Metals and Mott Insulators in SYK Models

TL;DR

This paper explores a dual-flavor SYK model revealing novel phases like strange half metals and Mott insulators, with phase transitions driven by temperature and flavor composition, advancing understanding of strongly correlated systems.

Contribution

It introduces a dual-flavor SYK model with arbitrary inter-flavor interactions, uncovering new phases and phase transitions not seen in single-flavor models.

Findings

Identification of a strange half metal phase with one gapless and one gapped flavor.

Discovery of a Mott insulating phase where both flavors are gapped.

Observation of phase transitions driven by temperature and flavor ratio.

Abstract

We study a dual flavor fermion model where each of the flavors form a Sachdev-Ye-Kitaev (SYK) system with arbitrary and possibly distinct $q$-body interactions. The crucial new element is an arbitrary all-to-all $r$-body interaction between the two flavors. At high temperatures the model shows a strange metal phase where both flavors are gapless, similar to the usual single flavor SYK model. Upon reducing temperature, the coupled system undergoes phase transitions to previously unseen phases - first, a strange half metal (SHM) phase where one flavor remains a strange metal while the other is gapped, and, second, a Mott insulating phase where both flavors are gapped. At a fixed low temperature we obtain transitions between these phases by tuning the relative fraction of sites for each flavor. We discuss the physics of these phases and the nature of transitions between them. This work provides an example of an instability of the strange metal with potential to provide new routes to study strongly correlated systems through the rich physics contained in SYK like models.