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Observation of intravalley phonon scattering of 2s excitons in MoSe2 and WSe2 monolayers

Observation of intravalley phonon scattering of 2s excitons in MoSe2 and WSe2 monolayers
Observation of intravalley phonon scattering of 2s excitons in MoSe2 and WSe2 monolayers
We present a high-resolution resonance Raman study of hBN encapsulated MoSe2 and WSe2 monolayers at 4 K using excitation energies from 1.6 eV to 2.25 eV. We report resonances with the WSe2 A2s and MoSe2 A2s and B2s excited Rydberg states despite their low oscillator strength. When resonant with the 2s states we identify new Raman peaks which are associated with intravalley scattering between different Rydberg states via optical phonons. By calibrating the Raman scattering efficiency and separately constraining the electric dipole matrix elements, we reveal that the scattering rates for k=0 optical phonons are comparable for both 1s and 2s states despite differences in the envelope functions. We also observe multiple new dispersive Raman peaks including a peak at the WSe2 A2s resonance that demonstrates non-linear dispersion and peak-splitting behavior that suggests the dispersion relations for dark excitonic states at energies near the 2s state are extremely complex.
Rydberg states, dark excitons, excited states, exciton phonon scattering, intervalley scattering, resonance raman spectroscopy, transition metal dichalcogenides
2053-1583
Mcdonnell, Liam
f2c05544-d580-4f52-bdec-1d74be0697d7
Viner, Jacob
0fe62a03-a774-43d2-a864-79af91de17eb
Rivera, Pasqual
e36a10b9-6779-4005-a4a8-ab11934145ae
Xu, Xiaodong
4e3760f2-d24d-47df-b827-8217e25e20ea
Smith, David C.
d9b2c02d-b7ea-498b-9ea1-208a1681536f
Mcdonnell, Liam
f2c05544-d580-4f52-bdec-1d74be0697d7
Viner, Jacob
0fe62a03-a774-43d2-a864-79af91de17eb
Rivera, Pasqual
e36a10b9-6779-4005-a4a8-ab11934145ae
Xu, Xiaodong
4e3760f2-d24d-47df-b827-8217e25e20ea
Smith, David C.
d9b2c02d-b7ea-498b-9ea1-208a1681536f

Mcdonnell, Liam, Viner, Jacob, Rivera, Pasqual, Xu, Xiaodong and Smith, David C. (2020) Observation of intravalley phonon scattering of 2s excitons in MoSe2 and WSe2 monolayers. 2D Materials, 7 (4), [045008]. (doi:10.1088/2053-1583/ab98f0).

Record type: Article

Abstract

We present a high-resolution resonance Raman study of hBN encapsulated MoSe2 and WSe2 monolayers at 4 K using excitation energies from 1.6 eV to 2.25 eV. We report resonances with the WSe2 A2s and MoSe2 A2s and B2s excited Rydberg states despite their low oscillator strength. When resonant with the 2s states we identify new Raman peaks which are associated with intravalley scattering between different Rydberg states via optical phonons. By calibrating the Raman scattering efficiency and separately constraining the electric dipole matrix elements, we reveal that the scattering rates for k=0 optical phonons are comparable for both 1s and 2s states despite differences in the envelope functions. We also observe multiple new dispersive Raman peaks including a peak at the WSe2 A2s resonance that demonstrates non-linear dispersion and peak-splitting behavior that suggests the dispersion relations for dark excitonic states at energies near the 2s state are extremely complex.

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Accepted/In Press date: 2 June 2020
Published date: 27 July 2020
Additional Information: Publisher Copyright: © 2020 IOP Publishing Ltd. Copyright: Copyright 2020 Elsevier B.V., All rights reserved.
Keywords: Rydberg states, dark excitons, excited states, exciton phonon scattering, intervalley scattering, resonance raman spectroscopy, transition metal dichalcogenides

Identifiers

Local EPrints ID: 442813
URI: http://eprints.soton.ac.uk/id/eprint/442813
ISSN: 2053-1583
PURE UUID: 4c82d6f4-b4b1-43d0-bbd9-d64a02b18323
ORCID for Liam Mcdonnell: ORCID iD orcid.org/0000-0002-0279-8947

Catalogue record

Date deposited: 28 Jul 2020 16:30
Last modified: 09 Jan 2022 07:53

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Contributors

Author: Liam Mcdonnell ORCID iD
Author: Jacob Viner
Author: Pasqual Rivera
Author: Xiaodong Xu
Author: David C. Smith

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