Nano-photocurrent Mapping of Local Electronic Structure in Twisted Bilayer Graphene

Sai S. Sunku; Alexander S. McLeod; Tobias Stauber; Hyobin Yoo; Dorri Halbertal; Guangxin Ni; Aaron Sternbach; Bor Yuan Jiang; Takashi Taniguchi; Kenji Watanabe; Philip Kim; Michael M. Fogler; D. N. Basov

doi:10.1021/acs.nanolett.9b04637

Nano-photocurrent Mapping of Local Electronic Structure in Twisted Bilayer Graphene

Sai S. Sunku, Alexander S. McLeod, Tobias Stauber, Hyobin Yoo, Dorri Halbertal, Guangxin Ni, Aaron Sternbach, Bor Yuan Jiang, Takashi Taniguchi, Kenji Watanabe, Philip Kim, Michael M. Fogler, D. N. Basov

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34 Scopus citations

Abstract

We report a combined nano-photocurrent and infrared nanoscopy study of twisted bilayer graphene (TBG) enabling access to the local electronic phenomena at length scales as short as 20 nm. We show that the photocurrent changes sign at carrier densities tracking the local superlattice density of states of TBG. We use this property to identify domains of varying local twist angle by local photothermoelectric effect. Consistent with the photocurrent study, infrared nanoimaging experiments reveal optical conductivity features dominated by twist-angle-dependent interband transitions. Our results provide a fast and robust method for mapping the electronic structure of TBG and suggest that similar methods can be broadly applied to probe electronic inhomogeneities of Moiré superlattices in other van der Waals heterostructures.

Original language	English (US)
Pages (from-to)	2958-2964
Number of pages	7
Journal	Nano letters
Volume	20
Issue number	5
DOIs	https://doi.org/10.1021/acs.nanolett.9b04637
State	Published - May 13 2020
Externally published	Yes

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Publisher Copyright:
Copyright © 2020 American Chemical Society.

Keywords

Moiré superlattice
interband transitions
nano-photocurrent
photothermoelectric effect
scanning near-field microscopy
twisted bilayer graphene

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title = "Nano-photocurrent Mapping of Local Electronic Structure in Twisted Bilayer Graphene",

abstract = "We report a combined nano-photocurrent and infrared nanoscopy study of twisted bilayer graphene (TBG) enabling access to the local electronic phenomena at length scales as short as 20 nm. We show that the photocurrent changes sign at carrier densities tracking the local superlattice density of states of TBG. We use this property to identify domains of varying local twist angle by local photothermoelectric effect. Consistent with the photocurrent study, infrared nanoimaging experiments reveal optical conductivity features dominated by twist-angle-dependent interband transitions. Our results provide a fast and robust method for mapping the electronic structure of TBG and suggest that similar methods can be broadly applied to probe electronic inhomogeneities of Moir{\'e} superlattices in other van der Waals heterostructures.",

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AU - Sunku, Sai S.

AU - McLeod, Alexander S.

AU - Stauber, Tobias

AU - Yoo, Hyobin

AU - Halbertal, Dorri

AU - Ni, Guangxin

AU - Sternbach, Aaron

AU - Jiang, Bor Yuan

AU - Taniguchi, Takashi

AU - Watanabe, Kenji

AU - Kim, Philip

AU - Fogler, Michael M.

AU - Basov, D. N.

PY - 2020/5/13

Y1 - 2020/5/13

N2 - We report a combined nano-photocurrent and infrared nanoscopy study of twisted bilayer graphene (TBG) enabling access to the local electronic phenomena at length scales as short as 20 nm. We show that the photocurrent changes sign at carrier densities tracking the local superlattice density of states of TBG. We use this property to identify domains of varying local twist angle by local photothermoelectric effect. Consistent with the photocurrent study, infrared nanoimaging experiments reveal optical conductivity features dominated by twist-angle-dependent interband transitions. Our results provide a fast and robust method for mapping the electronic structure of TBG and suggest that similar methods can be broadly applied to probe electronic inhomogeneities of Moiré superlattices in other van der Waals heterostructures.

AB - We report a combined nano-photocurrent and infrared nanoscopy study of twisted bilayer graphene (TBG) enabling access to the local electronic phenomena at length scales as short as 20 nm. We show that the photocurrent changes sign at carrier densities tracking the local superlattice density of states of TBG. We use this property to identify domains of varying local twist angle by local photothermoelectric effect. Consistent with the photocurrent study, infrared nanoimaging experiments reveal optical conductivity features dominated by twist-angle-dependent interband transitions. Our results provide a fast and robust method for mapping the electronic structure of TBG and suggest that similar methods can be broadly applied to probe electronic inhomogeneities of Moiré superlattices in other van der Waals heterostructures.

KW - Moiré superlattice

KW - interband transitions

KW - nano-photocurrent

KW - photothermoelectric effect

KW - scanning near-field microscopy

KW - twisted bilayer graphene

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Nano-photocurrent Mapping of Local Electronic Structure in Twisted Bilayer Graphene

Abstract

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Keywords

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