Deconfined Fermions but Confined Coherence?

TL;DR

This paper proposes a new theoretical framework for certain anisotropic materials like cuprate superconductors, where electrons are confined to lower-dimensional subspaces, explaining their mixed coherent and incoherent transport properties.

Contribution

It introduces a fixed point theory where electron coherence is confined to lower dimensions, reconciling anisotropic transport with Fermi surface evidence.

Findings

Transport is intrinsically incoherent in one direction at zero temperature.

Single electron coherence is confined to lower-dimensional subspaces.

The model explains anisotropic transport alongside Fermi surface signatures.

Abstract

The cuprate superconductors and certain organic conductors exhibit transport which is qualitatively anisotropic, yet at the same time other properties of these materials strongly suggest the existence of a Fermi surface and low energy excitations with substantial free electron character. The former of these features is very difficult to account for if the material possesses three dimensional coherence, while the latter is inconsistent with a description based on a two dimensional fixed point. We therefore present a new proposal for these materials in which they are categorized by a fixed point at which transport in one direction is not renormalization group irrelevant, but is intrinsically incoherent, i.e. the incoherence is present in a pure system, at zero temperature. The defining property of such a state is that single electron coherence is confined to lower dimensional subspaces (planes or chains) so that it is impossible to observe interference effects between histories which involve electrons moving between these subspaces.