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Title: Trion valley coherence in monolayer semiconductors

The emerging field of valleytronics aims to exploit the valley pseudospin of electrons residing near Bloch band extrema as an information carrier. Recent experiments demonstrating optical generation and manipulation of exciton valley coherence (the superposition of electron-hole pairs at opposite valleys) in monolayer transition metal dichalcogenides (TMDs) provide a critical step towards control of this quantum degree of freedom. The charged exciton (trion) in TMDs is an intriguing alternative to the neutral exciton for control of valley pseudospin because of its long spontaneous recombination lifetime, its robust valley polarization, and its coupling to residual electronic spin. Trion valley coherence has however been unexplored due to experimental challenges in accessing it spectroscopically. In this work, we employ ultrafast two-dimensional coherent spectroscopy to resonantly generate and detect trion valley coherence in monolayer MoSe 2 demonstrating that it persists for a few-hundred femtoseconds. We conclude that the underlying mechanisms limiting trion valley coherence are fundamentally different from those applicable to exciton valley coherence.
Authors:
 [1] ;  [1] ;  [1] ;  [2] ;  [1] ;  [1] ;  [2] ;  [2] ;  [1] ;  [3] ;  [1]
  1. Univ. of Texas, Austin, TX (United States)
  2. Univ. of Regensburg (Germany)
  3. National Inst. of Standards and Technology (NIST), Boulder, CO (United States)
Publication Date:
Grant/Contract Number:
SC0012670
Type:
Accepted Manuscript
Journal Name:
2D Materials
Additional Journal Information:
Journal Volume: 4; Journal Issue: 2; Journal ID: ISSN 2053-1583
Publisher:
IOP Publishing
Research Org:
Univ. of Texas, Austin, TX (United States). Energy Frontier Research Center (EFRC); Energy Frontier Research Centers (EFRC) (United States). Spins and Heat in Nanoscale Electronic Systems (SHINES)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
OSTI Identifier:
1463270

Hao, Kai, Xu, Lixiang, Wu, Fengcheng, Nagler, Philipp, Tran, Kha, Ma, Xin, Schüller, Christian, Korn, Tobias, MacDonald, Allan H., Moody, Galan, and Li, Xiaoqin. Trion valley coherence in monolayer semiconductors. United States: N. p., Web. doi:10.1088/2053-1583/aa70f9.
Hao, Kai, Xu, Lixiang, Wu, Fengcheng, Nagler, Philipp, Tran, Kha, Ma, Xin, Schüller, Christian, Korn, Tobias, MacDonald, Allan H., Moody, Galan, & Li, Xiaoqin. Trion valley coherence in monolayer semiconductors. United States. doi:10.1088/2053-1583/aa70f9.
Hao, Kai, Xu, Lixiang, Wu, Fengcheng, Nagler, Philipp, Tran, Kha, Ma, Xin, Schüller, Christian, Korn, Tobias, MacDonald, Allan H., Moody, Galan, and Li, Xiaoqin. 2017. "Trion valley coherence in monolayer semiconductors". United States. doi:10.1088/2053-1583/aa70f9. https://www.osti.gov/servlets/purl/1463270.
@article{osti_1463270,
title = {Trion valley coherence in monolayer semiconductors},
author = {Hao, Kai and Xu, Lixiang and Wu, Fengcheng and Nagler, Philipp and Tran, Kha and Ma, Xin and Schüller, Christian and Korn, Tobias and MacDonald, Allan H. and Moody, Galan and Li, Xiaoqin},
abstractNote = {The emerging field of valleytronics aims to exploit the valley pseudospin of electrons residing near Bloch band extrema as an information carrier. Recent experiments demonstrating optical generation and manipulation of exciton valley coherence (the superposition of electron-hole pairs at opposite valleys) in monolayer transition metal dichalcogenides (TMDs) provide a critical step towards control of this quantum degree of freedom. The charged exciton (trion) in TMDs is an intriguing alternative to the neutral exciton for control of valley pseudospin because of its long spontaneous recombination lifetime, its robust valley polarization, and its coupling to residual electronic spin. Trion valley coherence has however been unexplored due to experimental challenges in accessing it spectroscopically. In this work, we employ ultrafast two-dimensional coherent spectroscopy to resonantly generate and detect trion valley coherence in monolayer MoSe2 demonstrating that it persists for a few-hundred femtoseconds. We conclude that the underlying mechanisms limiting trion valley coherence are fundamentally different from those applicable to exciton valley coherence.},
doi = {10.1088/2053-1583/aa70f9},
journal = {2D Materials},
number = 2,
volume = 4,
place = {United States},
year = {2017},
month = {5}
}