Spin-charge separation and Kondo effect in transport through a 1D Mott-Hubbard insulator

TL;DR

This paper investigates how spin and charge transport behave in a finite 1D Mott-Hubbard insulator connected to reservoirs with different spin-dependent voltages, revealing a breakdown of spin-charge separation influenced by Kondo physics.

Contribution

It demonstrates the transition from spin-charge separation to a Fermi liquid regime in a 1D Mott insulator under non-equilibrium conditions, connecting to Kondo dot transport.

Findings

Breakdown of spin-charge separation with spin-dependent voltages.

Conditions for the validity of the large Hubbard gap approximation.

Relation of transport phenomena to Kondo physics in the Toulouse limit.

Abstract

We study low energy spin and charge transport through a 1D Mott-Hubbard insulator of finite length $L$ attached to Fermi liquid reservoirs characterized by different chemical potentials for electrons of opposite spin polarizations as it happens in quantum spin Hall insulators. We calculate the average currents (charge and spin) and their correlators and demonstrate how a transition induced by the reservoirs to the low energy Fermi liquid regime results in breakdown of the spin-charge separation, which is visible in the presence of the spin dependent voltages and a weak one electron scattering in the system. These calculations are carried out under assumption that the Hubbard gap 2M is large enough: $M > T_L \equiv v_c/L$ ($v_c$: charge velocity in the wire) and the scattering rate $\Gamma_s \ll T_L$. Relation of these results to Kondo dot transport in the Toulouse limit is also clarified.