Coherent dynamics of resonantly excited excitons in monolayers of transition metal dichalcogenides

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00216305%3A26620%2F20%3APU137341" target="_blank" >RIV/00216305:26620/20:PU137341 - isvavai.cz</a>

Výsledek na webu

<a href="https://www.spiedigitallibrary.org/conference-proceedings-of-spie/11278/2549229/Coherent-dynamics-of-resonantly-excited-excitons-in-monolayers-of-transition/10.1117/12.2549229.short?SSO=1" target="_blank" >https://www.spiedigitallibrary.org/conference-proceedings-of-spie/11278/2549229/Coherent-dynamics-of-resonantly-excited-excitons-in-monolayers-of-transition/10.1117/12.2549229.short?SSO=1</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1117/12.2549229" target="_blank" >10.1117/12.2549229</a>

Jazyk výsledku

angličtina

Název v původním jazyce

Coherent dynamics of resonantly excited excitons in monolayers of transition metal dichalcogenides

Popis výsledku v původním jazyce

We investigate dynamics of resonantly excited excitons in single-layers of MoSe2 and WS2 down to 4.5K. To this end, we measure the delay dependence of the heterodyne four-wave mixing (F M) amplitude induced by three, short laser pulses. This signal depends not only on the population of optically active excitons, which affects the absorption of the probe, but also on the population of optically inactive states, by interaction-induced energy shift, influencing the refractive index experienced by the probe. As such, it offers insight into density dynamics of excitons which do not directly couple to photons. Reproducing the coherent signal detected in amplitude and phase, the FWM delay dependence is modeled by a coherent superposition of several exponential decay components, with characteristic time constants from 0.1 picosecond up to 1 nanosecond. With increasing excitation intensity and/or temperature, we observe strong interference effects in the FWM field amplitude, resulting in progressively more complex and nonintuitive signal dynamics. We attribute this behaviour to increasingly populated exciton dark states, which change the FWM field phase by the relative effect on absorption and refractive index. We observe that exciton recombination occurs on a significantly longer timescale in WS2 with respect to MoSe2, which is attributed to the dark character of exciton ground state in the former and the bright in the latter.

Název v anglickém jazyce

Coherent dynamics of resonantly excited excitons in monolayers of transition metal dichalcogenides

Popis výsledku anglicky

We investigate dynamics of resonantly excited excitons in single-layers of MoSe2 and WS2 down to 4.5K. To this end, we measure the delay dependence of the heterodyne four-wave mixing (F M) amplitude induced by three, short laser pulses. This signal depends not only on the population of optically active excitons, which affects the absorption of the probe, but also on the population of optically inactive states, by interaction-induced energy shift, influencing the refractive index experienced by the probe. As such, it offers insight into density dynamics of excitons which do not directly couple to photons. Reproducing the coherent signal detected in amplitude and phase, the FWM delay dependence is modeled by a coherent superposition of several exponential decay components, with characteristic time constants from 0.1 picosecond up to 1 nanosecond. With increasing excitation intensity and/or temperature, we observe strong interference effects in the FWM field amplitude, resulting in progressively more complex and nonintuitive signal dynamics. We attribute this behaviour to increasingly populated exciton dark states, which change the FWM field phase by the relative effect on absorption and refractive index. We observe that exciton recombination occurs on a significantly longer timescale in WS2 with respect to MoSe2, which is attributed to the dark character of exciton ground state in the former and the bright in the latter.

Druh

D - Stať ve sborníku

CEP obor

—

OECD FORD obor

10302 - Condensed matter physics (including formerly solid state physics, supercond.)

Projekt

—

Návaznosti

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Rok uplatnění

2020

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Název statě ve sborníku

Proceedings of SPIE - The International Society for Optical Engineering

ISBN

978-15-10633-19-3

ISSN

0277-786X

e-ISSN

—

Počet stran výsledku

1

Strana od-do

„112781C“-„112781C“

Název nakladatele

Neuveden

Místo vydání

Neuveden

Místo konání akce

San Francisco

Datum konání akce

2. 2. 2020

Typ akce podle státní příslušnosti

WRD - Celosvětová akce

Kód UT WoS článku

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