Sign reversals of the quantum Hall effect and helicoidal magnetic-field-induced spin-density waves in quasi-one-dimensional organic conductors

TL;DR

This paper investigates how umklapp scattering influences magnetic-field-induced spin-density waves in quasi-one-dimensional organic conductors, explaining sign reversals of the quantum Hall effect and the transition to helicoidal SDWs.

Contribution

It demonstrates that umklapp processes can account for QHE sign reversals and polarization changes in SDWs within the quantized nesting model.

Findings

Umklapp scattering explains QHE sign reversals.

Transition from sinusoidal to helicoidal SDWs occurs.

Helicoidal SDWs exhibit a magnetoelectric effect.

Abstract

We study the effect of umklapp scattering on the magnetic-field-induced spin-density-wave phases, which are experimentally observed in the quasi-one-dimensional organic conductors of the Bechgaard salts family. Within the framework of the quantized nesting model, we show that umklapp processes may naturally explain sign reversals of the quantum Hall effect (QHE) observed in these conductors. Moreover, umklapp scattering can change the polarization of the spin-density wave (SDW) from linear (sinusoidal SDW) to circular (helicoidal SDW). The QHE vanishes in the helicoidal phases, but a magnetoelectric effect appears. These two characteristic properties may be utilized to detect the magnetic-field-induced helicoidal SDW phases experimentally.