2014
DOI: 10.1103/physrevb.90.041414
|View full text |Cite
|
Sign up to set email alerts
|

Exciton valley relaxation in a single layer ofWS2measured by ultrafast spectroscopy

Abstract: We measured the lifetime of optically created valley polarization in single layer WS 2 using transient absorption spectroscopy. The electron valley relaxation is very short (< 1ps). However the hole valley lifetime is at least two orders of magnitude longer and exhibits a temperature dependence that cannot be explained by single carrier spin/valley relaxation mechanisms. Our theoretical analysis suggests that a collective contribution of two potential processes may explain the valley relaxation in single layer… Show more

Help me understand this report
View preprint versions

Search citation statements

Order By: Relevance

Paper Sections

Select...
1
1
1
1

Citation Types

14
149
0

Year Published

2015
2015
2023
2023

Publication Types

Select...
8
1

Relationship

0
9

Authors

Journals

citations
Cited by 131 publications
(164 citation statements)
references
References 49 publications
(53 reference statements)
14
149
0
Order By: Relevance
“…Given that the effective bias added on the channel is on the order of V ds − ðE g + E exciton binding Þ ∼ 2.5 eV where we assume the band bending at both contacts is roughly of the electronic band gap at most and the mobility of 0.1-1 cm 2 · v=s of the devices (SI Appendix), the spin-free path indicates the estimated spin-valley lifetime around 10 1 ∼10 2 ns. This estimate is orders of magnitude larger than the valley lifetime estimated from polarization-resolved photoluminescence and pump-probe spectroscopy in which the exciton effect predominates the optical properties and consequently the valley lifetime of excitons instead of free carriers is probed (37,38). Note that the electron-hole exchange interaction provides the major channel for excitons' spinvalley depolarization (39), whereas the exchange interactions are greatly suppressed in oppositely drifting free carriers in a nearly intrinsic state, and consequently the free carriers presumably show significantly longer spin-valley lifetime.…”
Section: Resultsmentioning
confidence: 66%
“…Given that the effective bias added on the channel is on the order of V ds − ðE g + E exciton binding Þ ∼ 2.5 eV where we assume the band bending at both contacts is roughly of the electronic band gap at most and the mobility of 0.1-1 cm 2 · v=s of the devices (SI Appendix), the spin-free path indicates the estimated spin-valley lifetime around 10 1 ∼10 2 ns. This estimate is orders of magnitude larger than the valley lifetime estimated from polarization-resolved photoluminescence and pump-probe spectroscopy in which the exciton effect predominates the optical properties and consequently the valley lifetime of excitons instead of free carriers is probed (37,38). Note that the electron-hole exchange interaction provides the major channel for excitons' spinvalley depolarization (39), whereas the exchange interactions are greatly suppressed in oppositely drifting free carriers in a nearly intrinsic state, and consequently the free carriers presumably show significantly longer spin-valley lifetime.…”
Section: Resultsmentioning
confidence: 66%
“…Excitonic states in the MX 2 2D semiconductors (2DSCs) have been studied both theoretically and experimentally [12,13,[16][17][18][19][20] In both absorption and photoluminescence spectra, two strong exciton resonances are observed, commonly labelled A and B. They are associated with electronic transitions involving an electron and a hole (from the upper VB for A states and from the lower one for B states), with parallel spins.…”
Section: Arxiv:150909015v1 [Cond-matmes-hall] 30 Sep 2015mentioning
confidence: 99%
“…Neglecting the contributions of integrals involving atomic wave functions at different sites, the matrix elements in Eq. (33) can be simplified to nk|e −i(q+G)r |n k + q = P (q + G)S nk,n k+q (q + G), (34) where P (q + G) and S nk,n k (q + G) are defined above.…”
Section: B Screening Within the Random Phase Approximationmentioning
confidence: 99%
“…Note, however, that recent studies have started to elucidate various aspects of valley relaxation and decoherence in two-dimensional (2D) transition-metal dichalcogenides [32][33][34] and graphene [35,36], as well as carbon-based [19,37] and silicon quantum dots [38,39].…”
Section: Introductionmentioning
confidence: 99%