Electronic Liquid Crystal Phases of a Doped Mott Insulator

TL;DR

This paper explores how doping a Mott insulator leads to novel liquid-crystalline electronic phases, such as electron smectic and nematic states, which may explain behaviors observed in high-temperature superconductors.

Contribution

It introduces the concept of electron liquid-crystalline phases arising from stripe fluctuations in doped Mott insulators, extending the understanding of their ground states.

Findings

Existence of electron smectic and nematic phases due to stripe fluctuation dynamics.

Elimination of charge density wave transition by transverse stripe fluctuations.

Potential relevance of these phases to high-temperature superconductivity evidence.

Abstract

The character of the ground state of an antiferromagnetic insulator is fundamentally altered upon addition of even a small amount of charge. The added charges agglomerate along domain walls at which the spin correlations, which may or may not remain long-ranged, suffer a $\pi$ phase shift. In two dimensions, these domain walls are ``stripes'' which are either insulating, or conducting, i.e. metallic rivers with their own low energy degrees of freedom. However, quasi one-dimensional metals typically undergo a transition to an insulating ordered charge density wave (CDW) state at low temperatures. Here it is shown that such a transition is eliminated if the zero-point energy of transverse stripe fluctuations is sufficiently large in comparison to the CDW coupling between stripes. As a consequence, there exist novel, liquid-crystalline low-temperature phases -- an electron smectic, with crystalline order in one direction, but liquid-like correlations in the other, and an electron nematic with orientational order but no long-range positional order. These phases, which constitute new states of matter, can be either high temperature supeconductors or two-dimensional anisotropic ``metallic'' non-Fermi liquids. Evidence for the new phases may already have been obtained by neutron scattering experiments in the cuprate superconductor, La_{1.6-x}Nd_{0.4}Sr_xCuO_{4}.