Auger induced tunable trion-trion annihilation in monolayer WS<sub>2</sub>
ORAL
Abstract
Strong Coulomb interaction in monolayers (1L) of transition metal dichalcogenides (TMDCs) gives rise to exciton many-body effects. Exciton-exciton annihilation (EEA) is a known phenomenon [1,2] where one exciton non-radiatively recombines and provides its energy to another one, which forms free ‘hot’ electron-hole pair. In this regard, trion-trion annihilation (TTA) is nontrivial because of their like charges and has not been hitherto observed in these 1L-TMDCs.
In this work, we demonstrate TTA in a gated WS2 sample by using a pulsed excitation at low temperature (5 K). In particular, we observe that (1) the negative trion and biexciton exhibit an ‘anti-crossing’ like behavior with increasing ; (2) the trion PL intensity reduces gradually (while the biexciton intensity increases) in the spectral overlap region between trion and biexciton; and (3) the TRPL FWHM in the same region also indicates a faster trion decay. These three experimental observations indicate towards spectrally tunable Auger interaction between a bright and dark trion. We model the phenomenon using the Auger rate equation, which suggests a strong enhancement of the Auger rate when the spectral overlap between the trion and the charged biexciton is large.
References:
1. Daniel Erkensten et al, PRB, 103(4):045426, 2021.
2. Darwin F Cordovilla Leon et al, PRB, 100(24):241401, 2019.
In this work, we demonstrate TTA in a gated WS2 sample by using a pulsed excitation at low temperature (5 K). In particular, we observe that (1) the negative trion and biexciton exhibit an ‘anti-crossing’ like behavior with increasing ; (2) the trion PL intensity reduces gradually (while the biexciton intensity increases) in the spectral overlap region between trion and biexciton; and (3) the TRPL FWHM in the same region also indicates a faster trion decay. These three experimental observations indicate towards spectrally tunable Auger interaction between a bright and dark trion. We model the phenomenon using the Auger rate equation, which suggests a strong enhancement of the Auger rate when the spectral overlap between the trion and the charged biexciton is large.
References:
1. Daniel Erkensten et al, PRB, 103(4):045426, 2021.
2. Darwin F Cordovilla Leon et al, PRB, 100(24):241401, 2019.
*This work was supported in part by a Core Research Grant from the Science and Engineering Research Board (SERB) under Department of Science and Technology (DST), a grant from Indian Space Research Organization (ISRO), a grant from MHRD under STARS, and a grant from MHRD, MeitY and DST Nano Mission through NNetRA. Growth of hexagonal boron nitride crystals was supported by the Elemental Strategy Initiative conducted by the MEXT, Japan, Grant Number JPMXP0112101001, JSPS KAKENHI Grant Number JP20H00354 and JP19H05790.
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Presenters
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Suman Chatterjee
- Indian Institute of Science Bangalore