One-dimensional electron gas interacting with a Heisenberg spin-1/2 chain

TL;DR

This paper investigates a 1D electron gas coupled to a Heisenberg spin-1/2 chain, revealing a dominant odd-frequency singlet pairing mode and proposing a connection to the 2-leg ladder system at specific doping levels.

Contribution

It provides an analytical characterization of the gapless modes and identifies the dominant pairing symmetry in the coupled system, linking it to the Kondo-Heisenberg model.

Findings

The only gapless pairing mode is a composite odd-parity odd-frequency singlet.

The ordinary BCS pairing mode is incoherent in this system.

A 2-leg ladder can effectively realize the 1D Kondo-Heisenberg model at certain doping levels.

Abstract

We analyse a model of a one-dimensional electron gas interacting with an antiferromagnetic Heisenberg spin-1/2 chain via the spin exchange interactions. Using a solution at a special limit, we characterize the gapless modes of the spin gap fixed point at weak coupling $ J_{K}\ll J_{H},E_{F} $. we show that the only gapless pairing mode with divergent susceptibility is a composite odd-parity odd-frequency singlet pairing order parameter, while the ordinary BCS even-parity singlet pairing mode is incoherent. For 2-leg ladder systems, we note that it is possible to have a range of doping where the chemical potential cuts only the anti-bonding band while the bonding band remains half-filled. We propose that, in such a state, the 2-leg ladder is effectively realizing the one-dimensional Kondo-Heisenberg model.