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

doi:10.1021/acs.nanolett.3c01173

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 journal › Article › peer-review

9 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 language	English
Pages (from-to)	5201-5208
Number of pages	8
Journal	Nano Letters
Volume	23
Issue number	11
Early online date	26 May 2023
DOIs	https://doi.org/10.1021/acs.nanolett.3c01173
Publication status	Published - 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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Cite this

@article{cbc436fa8c964e02afdad05fb935e3b0,

title = "ARPES Signatures of Few-Layer Twistronic Graphenes",

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.",

keywords = "angle-resolved photoemission spectroscopy, flat band, graphene, twistronics, moir{\'e}",

author = "Nunn, {James E.} and Andrew Mcellistrim and Astrid Weston and Aitor Garcia-Ruiz and Watson, {Matthew D.} and Marcin Mucha-Kruczynski and Cephise Cacho and Gorbachev, {Roman V.} and Fal{\textquoteright}ko, {Vladimir I.} and Wilson, {Neil R.}",

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. ",

year = "2023",

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doi = "10.1021/acs.nanolett.3c01173",

language = "English",

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journal = "Nano Letters",

issn = "1530-6984",

publisher = "American Chemical Society",

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T1 - ARPES Signatures of Few-Layer Twistronic Graphenes

AU - Nunn, James E.

AU - Mcellistrim, Andrew

AU - Weston, Astrid

AU - Garcia-Ruiz, Aitor

AU - Watson, Matthew D.

AU - Mucha-Kruczynski, Marcin

AU - Cacho, Cephise

AU - Gorbachev, Roman V.

AU - Fal’ko, Vladimir I.

AU - Wilson, Neil R.

N1 - 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.

PY - 2023/6/14

Y1 - 2023/6/14

N2 - 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.

AB - 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.

KW - angle-resolved photoemission spectroscopy

KW - flat band

KW - graphene

KW - twistronics, moiré

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U2 - 10.1021/acs.nanolett.3c01173

DO - 10.1021/acs.nanolett.3c01173

M3 - Article

SN - 1530-6984

VL - 23

SP - 5201

EP - 5208

JO - Nano Letters

JF - Nano Letters

IS - 11

ER -

ARPES Signatures of Few-Layer Twistronic Graphenes

Abstract

Bibliographical note

Keywords

ASJC Scopus subject areas

Access to Document

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