Probing valley population imbalance in transition metal dichalcogenides via temperature-dependent second harmonic generation imaging

Abstract Degenerate minima in momentum space—valleys—provide an additional degree of freedom that can be used for information transport and storage. Notably, such minima naturally exist in the band structure of transition metal dichalcogenides (TMDs). When these atomically thin crystals interact wit...

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Autores principales:	Leonidas Mouchliadis, Sotiris Psilodimitrakopoulos, George Miltos Maragkakis, Ioanna Demeridou, George Kourmoulakis, Andreas Lemonis, George Kioseoglou, Emmanuel Stratakis
Formato:	article
Lenguaje:	EN
Publicado:	Nature Portfolio 2021
Materias:	Materials of engineering and construction. Mechanics of materials TA401-492 Chemistry QD1-999
Acceso en línea:	https://doaj.org/article/4c98b1d705af4efa89142e86d6ef4a0e
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spelling	oai:doaj.org-article:4c98b1d705af4efa89142e86d6ef4a0e2021-12-02T13:35:39ZProbing valley population imbalance in transition metal dichalcogenides via temperature-dependent second harmonic generation imaging10.1038/s41699-020-00183-z2397-7132https://doaj.org/article/4c98b1d705af4efa89142e86d6ef4a0e2021-01-01T00:00:00Zhttps://doi.org/10.1038/s41699-020-00183-zhttps://doaj.org/toc/2397-7132Abstract Degenerate minima in momentum space—valleys—provide an additional degree of freedom that can be used for information transport and storage. Notably, such minima naturally exist in the band structure of transition metal dichalcogenides (TMDs). When these atomically thin crystals interact with intense laser light, the second harmonic generated (SHG) field inherits special characteristics that reflect not only the broken inversion symmetry in real space but also the valley anisotropy in reciprocal space. The latter is present whenever there exists a valley population imbalance (VPI) between the two valleys and affects the polarization state of the detected SHG. In this work, it is shown that the temperature-induced change of the SHG intensity dependence on the excitation field polarization is a fingerprint of VPI in TMDs. In particular, pixel-by-pixel VPI mapping based on polarization-resolved raster-scanning imaging microscopy was performed inside a cryostat to generate the SHG contrast in the presence of VPI from every point of a TMD flake. The generated contrast is marked by rotation of the SHG intensity polar diagrams at low temperatures and is attributed to the VPI-induced SHG.Leonidas MouchliadisSotiris PsilodimitrakopoulosGeorge Miltos MaragkakisIoanna DemeridouGeorge KourmoulakisAndreas LemonisGeorge KioseoglouEmmanuel StratakisNature PortfolioarticleMaterials of engineering and construction. Mechanics of materialsTA401-492ChemistryQD1-999ENnpj 2D Materials and Applications, Vol 5, Iss 1, Pp 1-9 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	Materials of engineering and construction. Mechanics of materials TA401-492 Chemistry QD1-999
spellingShingle	Materials of engineering and construction. Mechanics of materials TA401-492 Chemistry QD1-999 Leonidas Mouchliadis Sotiris Psilodimitrakopoulos George Miltos Maragkakis Ioanna Demeridou George Kourmoulakis Andreas Lemonis George Kioseoglou Emmanuel Stratakis Probing valley population imbalance in transition metal dichalcogenides via temperature-dependent second harmonic generation imaging
description	Abstract Degenerate minima in momentum space—valleys—provide an additional degree of freedom that can be used for information transport and storage. Notably, such minima naturally exist in the band structure of transition metal dichalcogenides (TMDs). When these atomically thin crystals interact with intense laser light, the second harmonic generated (SHG) field inherits special characteristics that reflect not only the broken inversion symmetry in real space but also the valley anisotropy in reciprocal space. The latter is present whenever there exists a valley population imbalance (VPI) between the two valleys and affects the polarization state of the detected SHG. In this work, it is shown that the temperature-induced change of the SHG intensity dependence on the excitation field polarization is a fingerprint of VPI in TMDs. In particular, pixel-by-pixel VPI mapping based on polarization-resolved raster-scanning imaging microscopy was performed inside a cryostat to generate the SHG contrast in the presence of VPI from every point of a TMD flake. The generated contrast is marked by rotation of the SHG intensity polar diagrams at low temperatures and is attributed to the VPI-induced SHG.
format	article
author	Leonidas Mouchliadis Sotiris Psilodimitrakopoulos George Miltos Maragkakis Ioanna Demeridou George Kourmoulakis Andreas Lemonis George Kioseoglou Emmanuel Stratakis
author_facet	Leonidas Mouchliadis Sotiris Psilodimitrakopoulos George Miltos Maragkakis Ioanna Demeridou George Kourmoulakis Andreas Lemonis George Kioseoglou Emmanuel Stratakis
author_sort	Leonidas Mouchliadis
title	Probing valley population imbalance in transition metal dichalcogenides via temperature-dependent second harmonic generation imaging
title_short	Probing valley population imbalance in transition metal dichalcogenides via temperature-dependent second harmonic generation imaging
title_full	Probing valley population imbalance in transition metal dichalcogenides via temperature-dependent second harmonic generation imaging
title_fullStr	Probing valley population imbalance in transition metal dichalcogenides via temperature-dependent second harmonic generation imaging
title_full_unstemmed	Probing valley population imbalance in transition metal dichalcogenides via temperature-dependent second harmonic generation imaging
title_sort	probing valley population imbalance in transition metal dichalcogenides via temperature-dependent second harmonic generation imaging
publisher	Nature Portfolio
publishDate	2021
url	https://doaj.org/article/4c98b1d705af4efa89142e86d6ef4a0e
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Probing valley population imbalance in transition metal dichalcogenides via temperature-dependent second harmonic generation imaging

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