Spin Transitions in Graphene Butterflies at an Integer Filling Factor

TL;DR

This paper investigates how electron-electron interactions and periodic potentials influence spin transitions in graphene's fractal energy spectrum, explaining the unique magnetic field dependence of butterfly gaps observed in experiments.

Contribution

It introduces a theoretical framework that accounts for the interplay between interactions and periodicity, elucidating the physical mechanisms behind spin flip transitions in graphene.

Findings

Reentrant ferromagnetic states at different flux values

Suppression of ferromagnetic state at specific flux

Explanation of butterfly gap behavior in quantum Hall regime

Abstract

Recent experiments on the role of electron-electron interactions in fractal Dirac systems have revealed a host of interesting effects, in particular, the unique nature of the magnetic field dependence of butterfly gaps in graphene. The novel gap structure observed in the integer quantum Hall effect is quite intriguing [Nat. Phys. 10, 525 (2014)], where one observes a suppression of the ferromagnetic state at one value of the commensurable flux but a reentrant ferromagnetic state at another. Our present work that includes the interplay between the electron-electron interaction and the periodic potential, explains the underlying physical processes that can lead to such a unique behavior of the butterfly gaps in that system where spin flip transitions are involved in the ground state.