abstract

• We show that the light-matter interaction in monolayer WSe2 is strongly enhanced when the incoming electromagnetic wave is in resonance with the energy of the exciton states of strongly Coulomb bound electron-hole pairs below the electronic band gap. We perform second harmonic generation (SHG) spectroscopy as a function of laser energy and polarization at T=4K. At the exciton resonance energies we record an enhancement by up to 3 orders of magnitude of the SHG efficiency, due to the unusual combination of electric dipole and magnetic dipole transitions. The energy and parity of the exciton states showing the strong resonance effects are identified in 1- and 2-photon photoluminescence excitation experiments, corroborated by first principles calculations. Targeting the identified exciton states in resonant 2-photon excitation allows us to maximize k-valley coherence and polarization. © 2015 American Physical Society.

authors

• Amand T.
• Balocchi A.
• Bouet L.
• Gerber I.C.
• Lagarde D.
• Marie X.
• Urbaszek B.
• Vidal Borbolla Miguel Angel
• Wang G.

publication date

• 2015-01-01

funding provided via

• Seventh Framework Programme, FP7: 306719  Grant

published in

• Physical Review Letters  Journal

keywords

• Calculations; Electromagnetic waves; Energy gap; Excitons; Laser excitation; Monolayers; Nonlinear optics; Polarization; Resonance; Electronic band gaps; First-principles calculation; Light-matter interactions; Magnetic dipole transition; Optical second harmonics; Orders of magnitude; Photo-luminescence excitation; Second harmonic generation spectroscopies; Harmonic generation

Digital Object Identifier (DOI)

• 10.1103/PhysRevLett.114.097403

start page

end page

volume

• 114

issue

• 9