Effect of Spin Gap on Single-Hole Excitation Spectrum in the One-Dimensional t-J-J'Model

TL;DR

This paper investigates how a spin gap influences the single-hole excitation spectrum in a one-dimensional t-J-J' model, revealing changes in dispersion symmetry, spectral singularities, and quasiparticle weight due to the gap.

Contribution

It provides an analytical and numerical analysis of the single-hole spectral function in the gapped phase of the 1D t-J-J' model, highlighting new spectral features and quasiparticle behavior.

Findings

Dispersion symmetry around k=π/2 in the gapped phase

Suppression of holon band singularity with a spin gap

Finite quasiparticle weight Z_h due to hole-spin bound state

Abstract

We examine the effect of spin gap on single-hole spectral function in the one-dimensional t-J-J'model. At J'/J=1/2, where a dimer state is the ground state, an analytic expression is derived for J/t \to 0. At finite values of J/t, the numerical diagonalizations for finite-size clusters are performed. In contrast to the gapless case, we find that (i) the dispersion becomes symmetric around k=\pi/2, (ii) the singularity of the holon band is strongly suppressed, and (iii) the quasi-particle weight Z_{h} becomes finite at finite J/t. The feature (iii) is related to the presence of a bound state of the doped hole and an unpaired spin.