Magnetic-field-assisted electron confinement and valley splitting in strained graphene

TL;DR

This study demonstrates how strain-induced pseudomagnetic fields in graphene, combined with an external magnetic field, can confine electrons and lift valley degeneracy, revealing new electronic properties near Cu(111) step edges.

Contribution

It reports the experimental realization of strained graphene regions with controlled pseudomagnetic fields and shows their effect on electron confinement and valley splitting under magnetic fields.

Findings

Electron confinement observed at 8 Tesla in strained graphene.

Repetitive resonance peaks indicate valley degeneracy lifting.

Spatial modulation of Dirac points due to strain and charge transfer.

Abstract

Spatially varying strained graphene can acquire interesting electronic properties because of the strain-induced valley-dependent gauge (pseudomagnetic) fields1,2. Here we report the realization of strained graphene regions located close to the step edges of Cu(111), obtained by using thermal strain engineering3,4. We study these strained structures with sub-nanometre-resolved scanning tunnelling microscopy and spectroscopy and identify their spatially modulated Dirac points, demonstrating the effect of overlap of Cu and graphene wave functions on the charge transfer between them5. By applying a magnetic field of 8 Tesla, electron confinement, as revealed by regularly spaced sharp resonances6,7, is observed in the strained graphene. In some regions of the strained graphene, repetitive pairs of resonance peaks appear in the tunnelling spectra. This provides direct and compelling evidence for lifting of valley degeneracy due to the coexistence of both the magnetic field and the pseudomagnetic field.