Transport gap and hysteretic behavior of the Ising quantum Hall ferromagnets in Landau levels $\left\vert N\right\vert >0$ of bilayer graphene

TL;DR

This paper investigates the transport gap and hysteretic behavior of Ising quantum Hall ferromagnets in multilayer graphene, analyzing various excitations and their energies under different external conditions.

Contribution

It extends the understanding of Ising quantum Hall ferromagnetism to multilayer graphene and examines the transport gap and hysteresis phenomena in these systems.

Findings

Transport gap depends on excitations like electron-hole pairs and skyrmions.

Hysteretic behavior is linked to valley-pseudospin transitions.

Lowest energy excitations vary with Zeeman coupling, bias, and magnetic field.

Abstract

The chiral two-dimensional electron gas in Landau levels $\left\vert N\right\vert >0$ of a Bernal-stacked graphene bilayer has a valley-pseudospin Ising quantum Hall ferromagnetic behavior at odd filling factors $\nu _{N}=1,3$ of these fourfold degenerate states. At zero interlayer electrical bias, the ground state at these fillings is spin polarized and electrons occupy one valley or the other while a finite electrical bias produces a series of valley pseudospin-flip transitions. In this work, we extend the Ising behavior to chirally-stacked multilayer graphene and discuss the hysteretic behavior of the Ising quantum Hall ferromagnets. We compute the transport gap due to different excitations: bulk electron-hole pairs, electron-hole pairs confined to the coherent region of a valley-pseudospin domain wall, and spin or valley-pseudospin skyrmion-antiskyrmion pairs. We determine which of these excitations has the lowest energy at a given value of the Zeeman coupling, bias, and magnetic field.