Observation of electrically tunable van Hove singularities in twisted bilayer graphene from NanoARPES

DOI: 10.1002/adma.202001656

Authors: Alfred J. H. Jones (Aarhus University) , Ryan Muzzio (Carnegie Mellon University) , Paulina Majchrzak (Aarhus University) , Sahar Pakdel (Aarhus University) , Davide Curcio (Aarhus University) , Klara Volckaert (Aarhus University) , Deepnarayan Biswas (Aarhus University) , Jacob Gobbo (Carnegie Mellon University) , Simranjeet Singh (Carnegie Mellon University) , Jeremy T. Robinson (US Naval Research Laboratory) , Kenji Watanabe (National Institute for Materials Science, Japan) , Takashi Taniguchi (National Institute for Materials Science, Japan) , Timur K. Kim (Diamond Light Source) , Cephise Cacho (Diamond Light Source) , Nicola Lanata (Aarhus University) , Jill A. Miwa (Aarhus University) , Philip Hofmann (Aarhus University) , Jyoti Katoch (Carnegie Mellon University) , Soeren Ulstrup (Aarhus University)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Advanced Materials , VOL 104

State: Published (Approved)
Published: June 2020
Diamond Proposal Number(s): 24072

Abstract: The possibility of triggering correlated phenomena by placing a singularity of the density of states near the Fermi energy remains an intriguing avenue toward engineering the properties of quantum materials. Twisted bilayer gra- phene is a key material in this regard because the superlattice produced by the rotated graphene layers introduces a van Hove singularity and flat bands near the Fermi energy that cause the emergence of numerous correlated phases, including superconductivity. Direct demonstration of electrostatic control of the superlattice bands over a wide energy range has, so far, been critically missing. This work examines the effect of electrical doping on the electronic band structure of twisted bilayer graphene using a back-gated device archi- tecture for angle-resolved photoemission measurements with a nano-focused light spot. A twist angle of 12.2° is selected such that the superlattice Brillouin zone is sufficiently large to enable identification of van Hove singularities and flat band segments in momentum space. The doping dependence of these fea- tures is extracted over an energy range of 0.4 eV, expanding the combinations of twist angle and doping where they can be placed at the Fermi energy and thereby induce new correlated electronic phases in twisted bilayer graphene.

Journal Keywords: flat bands; nanoARPES; twisted bilayer graphene; van der Waals heterostructures; van Hove singularitys

Subject Areas: Physics, Materials


Instruments: I05-ARPES

Added On: 12/06/2020 09:57

Discipline Tags:

Quantum Materials Physics Hard condensed matter - structures Materials Science

Technical Tags:

Spectroscopy Angle Resolved Photoemission Spectroscopy (ARPES) Nano ARPES