Strained graphene structures: from valleytronics to pressure sensing

TL;DR

This paper explores how mechanical deformations in graphene can generate pseudo-magnetic fields and valley-polarized currents, and demonstrates its potential for pressure sensing with high sensitivity.

Contribution

It introduces methods to generate valley-polarized currents via local strain and shows how pressure-induced deformations affect graphene's resistance for sensing applications.

Findings

Pseudo-magnetic fields can exceed 300 T due to strain.

Valley-polarized currents are achievable through local deformation.

Graphene's resistance response is highly sensitive to bubble size and shape.

Abstract

Due to its strong bonds graphene can stretch up to 25% of its original size without breaking. Furthermore, mechanical deformations lead to the generation of pseudo-magnetic fields (PMF) that can exceed 300 T. The generated PMF has opposite direction for electrons originating from different valleys. We show that valley-polarized currents can be generated by local straining of multi-terminal graphene devices. The pseudo-magnetic field created by a Gaussian-like deformation allows electrons from only one valley to transmit and a current of electrons from a single valley is generated at the opposite side of the locally strained region. Furthermore, applying a pressure difference between the two sides of a graphene membrane causes it to bend/bulge resulting in a resistance change. We find that the resistance changes linearly with pressure for bubbles of small radius while the response becomes non-linear for bubbles that stretch almost to the edges of the sample. This is explained as due to the strong interference of propagating electronic modes inside the bubble. Our calculations show that high gauge factors can be obtained in this way which makes graphene a good candidate for pressure sensing.