Spin and Valley Splittings in Multilayered Massless Dirac Fermion System

TL;DR

This study investigates spin and valley splittings in a multilayered Dirac fermion system, revealing how magnetic fields and Coulomb interactions influence Landau level degeneracies and spin splitting at low temperatures.

Contribution

It demonstrates the detection of zero-mode Landau level spin splitting and the effect of magnetic fields on valley degeneracy in a multilayered Dirac fermion system.

Findings

Detection of zero-mode Landau level and its spin splitting.

Magnetic field enhances spin splitting due to Coulomb interactions.

Valley degeneracy breaks at high magnetic fields below 2K.

Abstract

The inter-layer magnetoresistance in a multilayered massless Dirac fermion system, $\alpha$-(BEDT-TTF)$_2$I$_3$, under hydrostatic pressure was investigated. We succeeded in detecting the zero-mode (n=0) Landau level and its spin splitting in the magnetic field normal to the 2D plane. We demonstrated that the effective Coulomb interaction in the magnetic field intensifies the spin splitting of zero-mode Landau carriers. At temperatures below 2K, magnetic fields above several Tesla break the twofold valley degeneracy.