Glassy dynamics in geometrically frustrated Coulomb liquids without disorder

TL;DR

This paper demonstrates that long-range Coulomb interactions in geometrically frustrated electron systems on triangular lattices lead to stripe order and a charge-glass state with slow dynamics, resembling experimental observations in organic materials.

Contribution

It reveals how Coulomb interactions lift degeneracy and induce stripe and glassy states in frustrated electron systems without disorder, a novel insight into charge-glass formation.

Findings

Stripe-ordered crystalline ground state stabilized

Emergence of amorphous stripe-glass metastable states

Slow, Arrhenius-like relaxation dynamics observed

Abstract

We show that introducing long-range Coulomb interactions immediately lifts the massive ground state degeneracy induced by geometric frustration for electrons on quarter-filled triangular lattices in the classical limit. Important consequences include the stabilization of a stripe-ordered crystalline (global) ground state, but also the emergence of very many low-lying metastable states with amorphous "stripe-glass" spatial structures. Melting of the stripe order thus leads to a frustrated Coulomb liquid at intermediate temperatures, showing remarkably slow (viscous) dynamics, with very long relaxation times growing in Arrhenius fashion upon cooling, as typical of strong glass formers. On shorter time scales, the system falls out of equilibrium and displays the aging phenomena characteristic of supercooled liquids above the glass transition. Our results show remarkable similarity with the recent observations of charge-glass behavior in ultra-clean triangular organic materials of the $\theta$-(BEDT-TTF)$_2$ family.