Continuous transition from a Landau quasiparticle to a neutral spinon

TL;DR

This paper introduces a wavefunction ansatz capturing a quantum transition from a charged Landau quasiparticle to a neutral spinon in a doped system, explaining unconventional ground states and strong pairing phenomena.

Contribution

It provides an explicit analytic wavefunction model for the transition from Landau quasiparticles to neutral spinons, supported by numerical simulations in a two-leg $t$-$J$ ladder.

Findings

The wavefunction accurately reproduces features from exact diagonalization and DMRG.

The transition involves a change from tight charge-spin binding to loosely-bound hole-spin pairs.

The hole carries a finite spin current but no charge current in the spinon regime.

Abstract

We examine a wavefunction ansatz in which a doped hole can experience a quantum transition from a charge $+e$ Landau quasiparticle to a neutral spinon as a function of the underlying spin-spin correlation. As shown variationally, such a wavefunction accurately captures all the essential features revealed by exact diagonalization and density matrix renormalization group simulations in a two-leg $t$-$J$ ladder. Hence its analytic form can provide an explicit understanding of the mechanism for the unconventional ground state. The transition in the phase diagram is accompanied by a change of the hole composite from a tight charge-spin binding to a loosely-bound hole-spin pair. In the latter, the hole carries a \emph{finite} spin current but with vanishing charge current in the degenerate ground states. We show that the charge of the hole composite here is dynamically diminished due to an internal relative hole-spin motion, which is fundamentally distinct from a simple charge-spin separation in a one-dimensional case. We further show that the same effect is also responsible for a strong pairing between two doped holes in such a non-Landau quasiparticle regime.