Gate-Tunable Tunneling Resistance in Graphene/Topological Insulator Vertical Junctions

TL;DR

This paper demonstrates a gate-tunable tunneling resistance in a graphene/Bi2Se3 heterojunction, revealing quantum oscillations and resistance maxima linked to quantum Hall states, advancing nanoelectronic device understanding.

Contribution

It reports the first experimental realization of a vertical heterojunction between graphene and a topological insulator with tunable tunneling properties.

Findings

Gate voltage effectively tunes tunneling resistance.

Quantum oscillations observed due to Landau levels.

Resistance maxima occur when graphene enters quantum Hall insulator state.

Abstract

Graphene-based vertical heterostructures, particularly stacks incorporated with other layered materials, are promising for nanoelectronics. The stacking of two model Dirac materials, graphene and topological insulator, can considerably enlarge the family of van der Waals heterostructures. Despite well understanding of the two individual materials, the electron transport properties of a combined vertical heterojunction are still unknown. Here we show the experimental realization of a vertical heterojunction between Bi2Se3 nanoplate and monolayer graphene. At low temperatures, the electron transport through the vertical heterojunction is dominated by the tunneling process, which can be effectively tuned by gate voltage to alter the density of states near the Fermi surface. In the presence of a magnetic field, quantum oscillations are observed due to the quantized Landau levels in both graphene and the two-dimensional surface states of Bi2Se3. Furthermore, we observe an exotic gate-tunable tunneling resistance under high magnetic field, which displays resistance maxima when the underlying graphene becomes a quantum Hall insulator.