Temperature-dependent excitonic superfluid plasma frequency evolution in an excitonic insulator, Ta2NiSe5

Abstract An interesting van der Waals material, Ta2NiSe5 has been known one of strong excitonic insulator candidates since it has very small or zero bandgap and can have a strong exciton binding energy because of its quasi-one-dimensional crystal structure. Here we investigate a single crystal Ta2Ni...

Descripción completa

Guardado en:

Detalles Bibliográficos
Autores principales:	Yu-Seong Seo, Man Jin Eom, Jun Sung Kim, Chang-Jong Kang, Byung Il Min, Jungseek Hwang
Formato:	article
Lenguaje:	EN
Publicado:	Nature Portfolio 2018
Materias:	Medicine R Science Q
Acceso en línea:	https://doaj.org/article/bdeb2a0a9ca944238fa0cd62ffc22873
Etiquetas:	Agregar Etiqueta Sin Etiquetas, Sea el primero en etiquetar este registro!

id	oai:doaj.org-article:bdeb2a0a9ca944238fa0cd62ffc22873
record_format	dspace
spelling	oai:doaj.org-article:bdeb2a0a9ca944238fa0cd62ffc228732021-12-02T15:08:07ZTemperature-dependent excitonic superfluid plasma frequency evolution in an excitonic insulator, Ta2NiSe510.1038/s41598-018-30430-92045-2322https://doaj.org/article/bdeb2a0a9ca944238fa0cd62ffc228732018-08-01T00:00:00Zhttps://doi.org/10.1038/s41598-018-30430-9https://doaj.org/toc/2045-2322Abstract An interesting van der Waals material, Ta2NiSe5 has been known one of strong excitonic insulator candidates since it has very small or zero bandgap and can have a strong exciton binding energy because of its quasi-one-dimensional crystal structure. Here we investigate a single crystal Ta2NiSe5 using optical spectroscopy. Ta2NiSe5 has quasi-one-dimensional chains along the a-axis. We have obtained anisotropic optical properties of a single crystal Ta2NiSe5 along the a- and c-axes. The measured a- and c-axis optical conductivities exhibit large anisotropic electronic and phononic properties. With regard to the a-axis optical conductivity, a sharp peak near 3050 cm−1 at 9 K, with a well-defined optical gap ($${{\boldsymbol{\Delta }}}_{{\boldsymbol{o}}{\boldsymbol{p}}}^{{\boldsymbol{E}}{\boldsymbol{I}}}\,{\boldsymbol{\simeq }}$$ ΔopEI≃ 1800 cm−1) and a strong temperature-dependence, is observed. With an increase in temperature, this peak broadens and the optical energy gap closes around ∼325 K ($${{\boldsymbol{T}}}_{{\boldsymbol{c}}}^{{\boldsymbol{E}}{\boldsymbol{I}}}$$ TcEI ). The spectral weight redistribution with respect to the frequency and temperature indicates that the normalized optical energy gap $$({{\boldsymbol{\Delta }}}_{{\boldsymbol{o}}{\boldsymbol{p}}}^{{\boldsymbol{E}}{\boldsymbol{I}}}({\boldsymbol{T}})/\,{{\boldsymbol{\Delta }}}_{{\boldsymbol{o}}{\boldsymbol{p}}}^{{\boldsymbol{E}}{\boldsymbol{I}}}{\bf{(0)}})$$ (ΔopEI(T)/ΔopEI(0)) is $${\bf{1}}{\boldsymbol{-}}{({\boldsymbol{T}}/{{\boldsymbol{T}}}_{{\boldsymbol{c}}}^{{\boldsymbol{E}}{\boldsymbol{I}}})}^{{\bf{2}}}$$ 1−(T/TcEI)2 . The temperature-dependent superfluid plasma frequency of the excitonic condensation in Ta2NiSe5 has been determined from measured optical data. Our study may pave new avenues in the future research on excitonic insulators.Yu-Seong SeoMan Jin EomJun Sung KimChang-Jong KangByung Il MinJungseek HwangNature PortfolioarticleMedicineRScienceQENScientific Reports, Vol 8, Iss 1, Pp 1-9 (2018)
institution	DOAJ
collection	DOAJ
language	EN
topic	Medicine R Science Q
spellingShingle	Medicine R Science Q Yu-Seong Seo Man Jin Eom Jun Sung Kim Chang-Jong Kang Byung Il Min Jungseek Hwang Temperature-dependent excitonic superfluid plasma frequency evolution in an excitonic insulator, Ta2NiSe5
description	Abstract An interesting van der Waals material, Ta2NiSe5 has been known one of strong excitonic insulator candidates since it has very small or zero bandgap and can have a strong exciton binding energy because of its quasi-one-dimensional crystal structure. Here we investigate a single crystal Ta2NiSe5 using optical spectroscopy. Ta2NiSe5 has quasi-one-dimensional chains along the a-axis. We have obtained anisotropic optical properties of a single crystal Ta2NiSe5 along the a- and c-axes. The measured a- and c-axis optical conductivities exhibit large anisotropic electronic and phononic properties. With regard to the a-axis optical conductivity, a sharp peak near 3050 cm−1 at 9 K, with a well-defined optical gap ($${{\boldsymbol{\Delta }}}_{{\boldsymbol{o}}{\boldsymbol{p}}}^{{\boldsymbol{E}}{\boldsymbol{I}}}\,{\boldsymbol{\simeq }}$$ ΔopEI≃ 1800 cm−1) and a strong temperature-dependence, is observed. With an increase in temperature, this peak broadens and the optical energy gap closes around ∼325 K ($${{\boldsymbol{T}}}_{{\boldsymbol{c}}}^{{\boldsymbol{E}}{\boldsymbol{I}}}$$ TcEI ). The spectral weight redistribution with respect to the frequency and temperature indicates that the normalized optical energy gap $$({{\boldsymbol{\Delta }}}_{{\boldsymbol{o}}{\boldsymbol{p}}}^{{\boldsymbol{E}}{\boldsymbol{I}}}({\boldsymbol{T}})/\,{{\boldsymbol{\Delta }}}_{{\boldsymbol{o}}{\boldsymbol{p}}}^{{\boldsymbol{E}}{\boldsymbol{I}}}{\bf{(0)}})$$ (ΔopEI(T)/ΔopEI(0)) is $${\bf{1}}{\boldsymbol{-}}{({\boldsymbol{T}}/{{\boldsymbol{T}}}_{{\boldsymbol{c}}}^{{\boldsymbol{E}}{\boldsymbol{I}}})}^{{\bf{2}}}$$ 1−(T/TcEI)2 . The temperature-dependent superfluid plasma frequency of the excitonic condensation in Ta2NiSe5 has been determined from measured optical data. Our study may pave new avenues in the future research on excitonic insulators.
format	article
author	Yu-Seong Seo Man Jin Eom Jun Sung Kim Chang-Jong Kang Byung Il Min Jungseek Hwang
author_facet	Yu-Seong Seo Man Jin Eom Jun Sung Kim Chang-Jong Kang Byung Il Min Jungseek Hwang
author_sort	Yu-Seong Seo
title	Temperature-dependent excitonic superfluid plasma frequency evolution in an excitonic insulator, Ta2NiSe5
title_short	Temperature-dependent excitonic superfluid plasma frequency evolution in an excitonic insulator, Ta2NiSe5
title_full	Temperature-dependent excitonic superfluid plasma frequency evolution in an excitonic insulator, Ta2NiSe5
title_fullStr	Temperature-dependent excitonic superfluid plasma frequency evolution in an excitonic insulator, Ta2NiSe5
title_full_unstemmed	Temperature-dependent excitonic superfluid plasma frequency evolution in an excitonic insulator, Ta2NiSe5
title_sort	temperature-dependent excitonic superfluid plasma frequency evolution in an excitonic insulator, ta2nise5
publisher	Nature Portfolio
publishDate	2018
url	https://doaj.org/article/bdeb2a0a9ca944238fa0cd62ffc22873
work_keys_str_mv	AT yuseongseo temperaturedependentexcitonicsuperfluidplasmafrequencyevolutioninanexcitonicinsulatorta2nise5 AT manjineom temperaturedependentexcitonicsuperfluidplasmafrequencyevolutioninanexcitonicinsulatorta2nise5 AT junsungkim temperaturedependentexcitonicsuperfluidplasmafrequencyevolutioninanexcitonicinsulatorta2nise5 AT changjongkang temperaturedependentexcitonicsuperfluidplasmafrequencyevolutioninanexcitonicinsulatorta2nise5 AT byungilmin temperaturedependentexcitonicsuperfluidplasmafrequencyevolutioninanexcitonicinsulatorta2nise5 AT jungseekhwang temperaturedependentexcitonicsuperfluidplasmafrequencyevolutioninanexcitonicinsulatorta2nise5
_version_	1718388277671624704

Temperature-dependent excitonic superfluid plasma frequency evolution in an excitonic insulator, Ta2NiSe5

Ejemplares similares