title: Enabling valley selective exciton scattering in monolayer WSe2through upconversion.
abstract: Excitons, Coulomb bound electron-hole pairs, are composite bosons and their interactions in traditional semiconductors lead to condensation and light amplification. The much stronger Coulomb interaction in transition metal dichalcogenides such as WSe2monolayers combined with the presence of the valley degree of freedom is expected to provide new opportunities for controlling excitonic effects. But so far the bosonic character of exciton scattering processes remains largely unexplored in these two-dimensional materials. Here we show that scattering between B-excitons and A-excitons preferably happens within the same valley in momentum space. This leads to power dependent, negative polarization of the hot B-exciton emission. We use a selective upconversion technique for efficient generation of B-excitons in the presence of resonantly excited A-excitons at lower energy; we also observe the excited A-excitons state 2s. Detuning of the continuous wave, low-power laser excitation outside the A-exciton resonance (with a full width at half maximum of 4 meV) results in vanishing upconversion signal.
authors.affiliation: Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Av. Rangueil, Toulouse 31077, France.
authors.forename: M
authors.initials: M
authors.lastname: Manca
authors.affiliation: Ioffe Institute, St Petersburg 194021, Russia.
authors.forename: M M
authors.initials: MM
authors.lastname: Glazov
authors.affiliation: Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Av. Rangueil, Toulouse 31077, France.
authors.forename: C
authors.initials: C
authors.lastname: Robert
authors.affiliation: Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Av. Rangueil, Toulouse 31077, France.
authors.forename: F
authors.initials: F
authors.lastname: Cadiz
authors.affiliation: National Institute for Materials Science, Tsukuba, Ibaraki 305-0044, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Taniguchi
authors.affiliation: National Institute for Materials Science, Tsukuba, Ibaraki 305-0044, Japan.
authors.forename: K
authors.identifier: 0000-0003-3701-8119
authors.initials: K
authors.lastname: Watanabe
authors.affiliation: Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Av. Rangueil, Toulouse 31077, France.
authors.forename: E
authors.initials: E
authors.lastname: Courtade
authors.affiliation: Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Av. Rangueil, Toulouse 31077, France.
authors.forename: T
authors.initials: T
authors.lastname: Amand
authors.affiliation: Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Av. Rangueil, Toulouse 31077, France.
authors.forename: P
authors.initials: P
authors.lastname: Renucci
authors.affiliation: Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Av. Rangueil, Toulouse 31077, France.
authors.forename: X
authors.initials: X
authors.lastname: Marie
authors.affiliation: Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Av. Rangueil, Toulouse 31077, France.
authors.forename: G
authors.initials: G
authors.lastname: Wang
authors.affiliation: Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Av. Rangueil, Toulouse 31077, France.
authors.forename: B
authors.identifier: 0000-0003-0226-7983
authors.initials: B
authors.lastname: Urbaszek