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Title: Detection of thermodynamic "valley noise" in monolayer semiconductors: access to intrinsic valley relaxation timescales

Together with charge and spin, many novel two-dimensional materials also permit information to be encoded in an electron’s valley degree of freedom—that is, in particular momentum states in the material’s Brillouin zone. With a view toward valley-based (opto)electronic technologies, the intrinsic time scales of valley scattering are therefore of fundamental interest. Here, we demonstrate an entirely noise-based approach for exploring valley dynamics in monolayer transition-metal dichalcogenide semiconductors. Exploiting their valley-specific optical selection rules, we use optical Faraday rotation to passively detect the thermodynamic fluctuations of valley polarization in a Fermi sea of resident carriers. This spontaneous “valley noise” reveals narrow Lorentzian line shapes and, therefore, long exponentially-decaying intrinsic valley relaxation. Moreover, the noise signatures validate both the relaxation times and the spectral dependence of conventional (perturbative) pump-probe measurements. These results provide a viable route toward quantitative measurements of intrinsic valley dynamics, free from any external perturbation, pumping, or excitation.
Authors:
ORCiD logo [1] ; ORCiD logo [1] ;  [2] ;  [2] ;  [1]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  2. Univ. of Washington, Seattle, WA (United States)
Publication Date:
Report Number(s):
LA-UR-18-27841
Journal ID: ISSN 2375-2548
Grant/Contract Number:
89233218CNA000001
Type:
Accepted Manuscript
Journal Name:
Science Advances
Additional Journal Information:
Journal Volume: 5; Journal Issue: 3; Journal ID: ISSN 2375-2548
Publisher:
AAAS
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; High Magnetic Field Science
OSTI Identifier:
1501810

Goryca, Mateusz Marek, Crooker, Scott A., Xu, Xiaodong, Wilson, Nathan, and Dey, Prasenjit. Detection of thermodynamic "valley noise" in monolayer semiconductors: access to intrinsic valley relaxation timescales. United States: N. p., Web. doi:10.1126/sciadv.aau4899.
Goryca, Mateusz Marek, Crooker, Scott A., Xu, Xiaodong, Wilson, Nathan, & Dey, Prasenjit. Detection of thermodynamic "valley noise" in monolayer semiconductors: access to intrinsic valley relaxation timescales. United States. doi:10.1126/sciadv.aau4899.
Goryca, Mateusz Marek, Crooker, Scott A., Xu, Xiaodong, Wilson, Nathan, and Dey, Prasenjit. 2019. "Detection of thermodynamic "valley noise" in monolayer semiconductors: access to intrinsic valley relaxation timescales". United States. doi:10.1126/sciadv.aau4899. https://www.osti.gov/servlets/purl/1501810.
@article{osti_1501810,
title = {Detection of thermodynamic "valley noise" in monolayer semiconductors: access to intrinsic valley relaxation timescales},
author = {Goryca, Mateusz Marek and Crooker, Scott A. and Xu, Xiaodong and Wilson, Nathan and Dey, Prasenjit},
abstractNote = {Together with charge and spin, many novel two-dimensional materials also permit information to be encoded in an electron’s valley degree of freedom—that is, in particular momentum states in the material’s Brillouin zone. With a view toward valley-based (opto)electronic technologies, the intrinsic time scales of valley scattering are therefore of fundamental interest. Here, we demonstrate an entirely noise-based approach for exploring valley dynamics in monolayer transition-metal dichalcogenide semiconductors. Exploiting their valley-specific optical selection rules, we use optical Faraday rotation to passively detect the thermodynamic fluctuations of valley polarization in a Fermi sea of resident carriers. This spontaneous “valley noise” reveals narrow Lorentzian line shapes and, therefore, long exponentially-decaying intrinsic valley relaxation. Moreover, the noise signatures validate both the relaxation times and the spectral dependence of conventional (perturbative) pump-probe measurements. These results provide a viable route toward quantitative measurements of intrinsic valley dynamics, free from any external perturbation, pumping, or excitation.},
doi = {10.1126/sciadv.aau4899},
journal = {Science Advances},
number = 3,
volume = 5,
place = {United States},
year = {2019},
month = {3}
}

Works referenced in this record:

Valley filter and valley valve in graphene
journal, February 2007
  • Rycerz, A.; Tworzyd?o, J.; Beenakker, C. W. J.
  • Nature Physics, Vol. 3, Issue 3, p. 172-175
  • DOI: 10.1038/nphys547