Weak localization and magnetoresistance in a two-leg ladder model

TL;DR

This paper investigates how magnetic fields influence weak localization and magnetoresistance in a two-leg ladder model, revealing complex behaviors including negative and positive magnetoresistance and oscillations, depending on the magnetic field strength.

Contribution

It provides a detailed analysis of magnetoresistance effects in a two-leg ladder model, highlighting the role of magnetic fields in chain decoupling and localization phenomena, which was not previously understood.

Findings

Magnetic field causes negative magnetoresistance due to weak localization.

Strong magnetic fields lead to effective decoupling of the chains.

Magnetoresistance oscillations originate from low-energy collective excitations.

Abstract

We analyze the weak localization correction to the conductivity of a spinless two-leg ladder model in the limit of strong dephasing \tau_\phi << \tau_tr, paying particular attention to the presence of a magnetic field, which leads to an unconventional magnetoresistance behavior. We find that the magnetic field leads to three different effects: (i) negative magnetoresistance due to the regular weak localization correction (ii) effective decoupling of the two chains, leading to positive magnetoresistance and (iii) oscillations in the magnetoresistance originating from the nature of the low-energy collective excitations. All three effects can be observed depending on the parameter range, but it turns out that large magnetic fields always decouple the chains and thus lead to the curious effect of magnetic field enhanced localization.