Evidence for interior-gap pair-density-wave state in Kondo-Heisenberg chains

TL;DR

This paper provides evidence that one-dimensional Kondo-Heisenberg models exhibit an interior-gap pair-density-wave state driven by strong correlations, with characteristic momentum structures and dominant superconducting correlations.

Contribution

It demonstrates the realization of an interior-gap PDW state in strongly correlated Kondo-Heisenberg chains using advanced DMRG techniques, revealing dynamic emergence of interior-gap features.

Findings

PDW correlation is dominant in the spin-gapped regime.

Momentum distribution shows interior-gap-like structures, including a dip for S=3/2 chains.

Boundary effects significantly influence real-space correlations, requiring thermodynamic-limit analysis.

Abstract

Interior-gap superconductivity has long been discussed as an exotic paired state in the presence of Fermi-surface mismatch, but its realization in canonical strongly correlated models has remained elusive. Here we present evidence that the superconducting phase of one-dimensional Kondo-Heisenberg models realizes an interior-gap pair-density-wave (PDW) state generated by strong correlations. Combining infinite density-matrix-renormalization-group (iDMRG) and finite DMRG calculations for $S=1/2$ and $S=3/2$ chains, we show that the PDW correlation is the dominant bulk superconducting correlation in the spin-gapped regime and that the momentum distribution function $n(k)$ exhibits a reconstructed structure characteristic of interior-gap physics. In particular, while the feature in $n(k)$ for the $S=1/2$ chain is only hump-like, the corresponding structure in the $S=3/2$ chain develops into a clear dip, strongly supporting the interpretation in terms of an interior-gap-like dip structure. Unlike conventional interior-gap scenarios based on a mismatch between preexisting Fermi surfaces, the present system starts from a single bare conduction-electron Fermi surface, and the additional low-energy single-particle structure emerges dynamically together with the dominant PDW correlation through the Kondo coupling. Finite DMRG data further demonstrate that boundary effects can substantially modify real-space correlations in this gapless one-dimensional system, making a direct thermodynamic-limit calculation essential for identifying the intrinsic bulk momentum structure and the dominant correlation channel.