Advanced van der Waals technologies for probing electronic properties of graphene based heterostructures

Abstract

Richard P. Feynman once said "when we have some control of the arrangement of things on a small scale we will get an enormously greater range of possible properties that substances can have, and of different things that we can do". This foresight has now been realized in the regime of two-dimensional (2D) materials, which could be artificially assembled into van der Waals (vdW) heterostructures with on-demand properties. The development of ingenious experimental techniques has created a new paradigm for electronic devices with dramatic performance and enabled exploration of novel physical phenomena. This work is dedicated to advanced vdW technologies for probing novel electronic properties of graphene based heterostructures. The work consists of two themes. In the first theme, we focus on rhombohedral graphite, which is rarely studied yet with intrinsic fascinating electronic properties. The lack of control of the stacking sequence limits most research to the more stable Bernal form of graphite. This work presents the directional encapsulation of rhombohedral graphite crystallites with hexagonal boron nitride (hBN) along the graphite zigzag edges. Facilitated by this improved vdW technique, we obtained high-quality rhombohedral graphite devices and studied their transport properties. We observed the gap opening and quantum Hall effect of the topologically protected surface states. In the quantum Hall regime, rhombohedral graphite exhibits transition between a gapless semimetallic phase and a gapped quantum spin Hall phase with giant Berry curvature. For thinner graphite (

Date of Award	31 Dec 2021
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Konstantin Novoselov (Supervisor) & Artem Mishchenko (Supervisor)