Magnetic field-tunable valley-contrasting pseudomagnetic confinement in graphene

TL;DR

This paper demonstrates that in strained graphene, inhomogeneous pseudomagnetic fields can create valley-contrasting quantum confinement of Dirac fermions, which can be tuned with real magnetic fields to manipulate valley polarization.

Contribution

The study experimentally shows that pseudomagnetic fields in strained graphene can induce valley-contrasting confinement, enabling control over valley polarization with magnetic tuning.

Findings

Valley-contrasting spatial confinement observed in strained graphene.

Tuning real magnetic field balances effective fields in valleys.

Field-tunable valley-polarized confined states achieved.

Abstract

Introducing quantum confinement has uncovered a rich set of interesting quantum phenomena and allows one to directly probe the physics of confined (quasi-)particles. In most experiments, however, electrostatic potential is the only available method to generate the quantum confinement in a continuous system. Here, we demonstrated experimentally that inhomogeneous pseudomagnetic fields in strained graphene can introduce exotic quantum confinement of massless Dirac fermions. The pseudomagnetic fields have opposite directions in the two distinct valleys of graphene. By tuning real magnetic field, the total effective magnetic fields in the two valleys are imbalanced. Then, we realized valley-contrasting spatial confinement, which lifts the valley degeneracy and results in field-tunable valley-polarized confined states in graphene. Our results provide a new avenue to manipulate the valley degree of freedom.