Mode-Resolved Multiband Ballistic Transport and Conductance Thresholds in Bilayer Graphene Junctions

TL;DR

This paper investigates how electrostatic gating, interlayer bias, and strain influence ballistic transport and conductance in bilayer graphene junctions, revealing a multiband transport fingerprint and control mechanisms.

Contribution

It introduces a comprehensive framework for understanding angle-resolved transport in bilayer graphene, highlighting multiband effects and the role of strain as a geometric control.

Findings

Interlayer bias opens a tunable transport gap.

Identification of a conductance threshold for upper band propagation.

Strain redistributes transmission angles without disorder effects.

Abstract

We study ballistic transport in bilayer graphene junctions and show how electrostatic gating, interlayer bias, and homogeneous strain provide complementary control over electron transmission. In the absence of strain, transport is governed by symmetry constraints that suppress transmission at specific incidence angles despite the availability of states. An interlayer bias lifts this suppression through mode mixing and opens a tunable transport gap. Within a full four-band description, we identify a distinct conductance threshold that marks the onset of propagation of the upper band inside the barrier. This produces a clear change in the slope of the conductance and serves as an experimentally accessible transport fingerprint of the multiband structure and interlayer coupling. Homogeneous in-plane strain acts as a geometric control mechanism. By reshaping the band structure in momentum space, it redistributes the angular transmission window and suppresses conductance without introducing disorder. Importantly, strain preserves the underlying symmetry-based decoupling responsible for transmission suppression while shifting its condition away from normal incidence. These results provide a unified framework for interpreting angle-resolved transport in bilayer graphene and establish multiband ballistic transport as a practical probe of band-structure geometry.