ARPES Signatures of Few-Layer Twistronic Graphenes

James E. Nunn, Andrew Mcellistrim, Astrid Weston, Aitor Garcia-Ruiz, Matthew D. Watson, Marcin Mucha-Kruczynski, Cephise Cacho, Roman V. Gorbachev, Vladimir I. Fal’ko, Neil R. Wilson

Research output: Contribution to journalArticlepeer-review

5 Citations (SciVal)

Abstract

Diverse emergent correlated electron phenomena have been observed in twisted-graphene layers. Many electronic structure predictions have been reported exploring this new field, but with few momentum-resolved electronic structure measurements to test them. We use angle-resolved photoemission spectroscopy to study the twist-dependent (1° < θ < 8°) band structure of twisted-bilayer, monolayer-on-bilayer, and double-bilayer graphene (tDBG). Direct comparison is made between experiment and theory, using a hybrid k·p model for interlayer coupling. Quantitative agreement is found across twist angles, stacking geometries, and back-gate voltages, validating the models and revealing field-induced gaps in twisted graphenes. However, for tDBG at θ = 1.5 ± 0.2°, close to the magic angle θ = 1.3°, a flat band is found near the Fermi level with measured bandwidth Ew = 31 ± 5 meV. An analysis of the gap between the flat band and the next valence band shows deviations between experiment (Δh = 46 ± 5 meV) and theory (Δh = 5 meV), indicative of lattice relaxation in this regime.

Original languageEnglish
Pages (from-to)5201-5208
Number of pages8
JournalNano Letters
Volume23
Issue number11
Early online date26 May 2023
DOIs
Publication statusPublished - 14 Jun 2023

Bibliographical note

Data Availability
The data that support the plots in the manuscript are available from the corresponding authors upon reasonable request.

We acknowledge support from the Royal Society, ERC Consolidator grant QTWIST (101001515) and European Graphene Flagship Core3 Project, EPSRC grants EP/V007033/1, EP/S030719/1 and EP/V026496/1, EP/T027207/1, P/W006502/1 and EP/S030719/1. A.M. was supported by the EPSRC CDT Graphene-NOWNANO.

Funding Information:
We thank Diamond Light Source for beamtime (proposals SI20573, SI28919, and SI32737). We acknowledge support from the Royal Society, ERC Consolidator grant QTWIST (101001515) and European Graphene Flagship Core3 Project, EPSRC grants EP/V007033/1, EP/S030719/1 and EP/V026496/1, EP/T027207/1, P/W006502/1 and EP/S030719/1. A.M. was supported by the EPSRC CDT Graphene-NOWNANO.

Keywords

  • angle-resolved photoemission spectroscopy
  • flat band
  • graphene
  • twistronics, moiré

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Mechanical Engineering
  • Bioengineering
  • General Chemistry
  • General Materials Science

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