skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Exchange-driven intravalley mixing of excitons in monolayer transition metal dichalcogenides

Journal Article · · Nature Physics
 [1]; ORCiD logo [2]; ORCiD logo [2];  [1]; ORCiD logo [3]; ORCiD logo [2];  [4]
  1. Univ. of California, Berkeley, CA (United States). Dept. of Chemistry; Kavli Energy Nanoscience Inst. at Berkeley, CA (United States)
  2. Univ. of California, Berkeley, CA (United States). Dept. of Physics; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials Sciences Division
  3. National Tsing Hua Univ., Hsinchu (Taiwan). Materials Sciences and Engineering
  4. Univ. of California, Berkeley, CA (United States). Dept. of Chemistry; Kavli Energy Nanoscience Inst. at Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Biophysics and Integrated Bioimaging Division

Monolayer transition metal dichalcogenides (TMDCs) are promising two-dimensional (2D) semiconductors for application in optoelectronics. Their optical properties are dominated by two series of photo-excited exciton states—A (XA) and B (XB)1,2—that are derived from direct interband transitions near the band extrema. These exciton states have large binding energies and strong optical absorption3,4,5,6, and form an ideal system to investigate many-body effects in low dimensions. Because spin–orbit coupling causes a large splitting between bands of opposite spins, XA and XB are usually treated as spin-polarized Ising excitons, each arising from interactions within a specific set of states induced by interband transitions between pairs of either spin-up or spin-down bands (TA or TB). Here, by using monolayer MoS2 as a prototypical system and solving the first-principles Bethe–Salpeter equations, we demonstrate a strong intravalley exchange interaction between TA and TB, indicating that XA and XB are mixed states instead of pure Ising excitons. Using 2D electronic spectroscopy, we observe that an optical excitation of the lower-energy TA induces a population of the higher-energy TB, manifesting the intravalley exchange interaction. This work elucidates the dynamics of exciton formation in monolayer TMDCs, and sheds light on many-body effects in 2D materials.

Research Organization:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). LBNL Materials Project
Sponsoring Organization:
USDOE; USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Materials Sciences & Engineering Division
DOE Contract Number:
AC02-05CH11231
OSTI ID:
1530822
Journal Information:
Nature Physics, Vol. 15, Issue 3; ISSN 1745-2473
Country of Publication:
United States
Language:
English

References (45)

Atomically Thin MoS2 A New Direct-Gap Semiconductor journal September 2010
Emerging Photoluminescence in Monolayer MoS2 journal April 2010
Optical Spectrum of MoS 2 : Many-Body Effects and Diversity of Exciton States journal November 2013
Giant bandgap renormalization and excitonic effects in a monolayer transition metal dichalcogenide semiconductor journal August 2014
Probing excitonic dark states in single-layer tungsten disulphide journal August 2014
Exciton Binding Energy and Nonhydrogenic Rydberg Series in Monolayer WS 2 journal August 2014
Fine structure of quantum well excitons journal January 1990
Exchange interaction and polariton effects in quantum-well excitons journal April 1990
Subpicosecond spin relaxation dynamics of excitons and free carriers in GaAs quantum wells journal December 1991
Exciton spin dynamics in quantum wells journal June 1993
Exciton dynamics in GaAs quantum wells under resonant excitation journal October 1994
Valley depolarization due to intervalley and intravalley electron-hole exchange interactions in monolayer MoS 2 journal May 2014
Optical generation of excitonic valley coherence in monolayer WSe2 journal August 2013
Direct measurement of exciton valley coherence in monolayer WSe2 journal February 2016
Dirac cones and Dirac saddle points of bright excitons in monolayer transition metal dichalcogenides journal May 2014
Nonanalyticity, Valley Quantum Phases, and Lightlike Exciton Dispersion in Monolayer Transition Metal Dichalcogenides: Theory and First-Principles Calculations journal October 2015
Exciton band structure of monolayer MoS 2 journal February 2015
Many-Body Effects in Valleytronics: Direct Measurement of Valley Lifetimes in Single-Layer MoS 2 journal December 2013
Coherent Electronic Coupling in Atomically Thin MoSe 2 journal May 2014
Coherent and Incoherent Coupling Dynamics between Neutral and Charged Excitons in Monolayer MoSe 2 journal July 2016
Tightly bound trions in monolayer MoS2 journal December 2012
Two-dimensional spectroscopy of electronic couplings in photosynthesis journal March 2005
Long-lived quantum coherence in photosynthetic complexes at physiological temperature journal July 2010
Many-Body Interactions in Semiconductors Probed by Optical Two-Dimensional Fourier Transform Spectroscopy journal February 2006
Two-Dimensional Electronic Spectroscopy Reveals the Dynamics of Phonon-Mediated Excitation Pathways in Semiconducting Single-Walled Carbon Nanotubes journal January 2012
Intrinsic homogeneous linewidth and broadening mechanisms of excitons in monolayer transition metal dichalcogenides journal September 2015
Measurement of Ultrafast Excitonic Dynamics of Few-Layer MoS 2 Using State-Selective Coherent Multidimensional Spectroscopy journal October 2015
Excitonic luminescence upconversion in a two-dimensional semiconductor journal December 2015
Long-lived nanosecond spin relaxation and spin coherence of electrons in monolayer MoS2 and WS2 journal August 2015
BerkeleyGW: A massively parallel computer package for the calculation of the quasiparticle and optical properties of materials and nanostructures journal June 2012
QUANTUM ESPRESSO: a modular and open-source software project for quantum simulations of materials journal September 2009
Electron correlation in semiconductors and insulators: Band gaps and quasiparticle energies journal October 1986
Nonuniform sampling schemes of the Brillouin zone for many-electron perturbation-theory calculations in reduced dimensionality journal January 2017
Coulomb-hole summations and energies for G W calculations with limited number of empty orbitals: A modified static remainder approach journal April 2013
wannier90: A tool for obtaining maximally-localised Wannier functions journal May 2008
Electron-Hole Excitations in Semiconductors and Insulators journal September 1998
Electron-hole excitations and optical spectra from first principles journal August 2000
Design, Modeling, and Fabrication of Chemical Vapor Deposition Grown MoS 2 Circuits with E-Mode FETs for Large-Area Electronics journal September 2016
From Bulk to Monolayer MoS2: Evolution of Raman Scattering journal January 2012
Sub-8-fs pulses from an ultrabroadband optical parametric amplifier in the visible journal January 1998
Pulse-front-matched optical parametric amplification for sub-10-fs pulse generation tunable in the visible and near infrared journal January 1998
Pulse-front matching of ultrabroadband near-infrared noncollinear optical parametric amplified pulses journal January 2009
Phase-stabilized two-dimensional electronic spectroscopy journal September 2004
Rapid and economical data acquisition in ultrafast frequency-resolved spectroscopy using choppers and a microcontroller journal January 2016
Room-Temperature Coherent Optical Phonon in 2D Electronic Spectra of CH 3 NH 3 PbI 3 Perovskite as a Possible Cooling Bottleneck journal June 2017

Related Subjects