title: Anisotropic Particle-Hole Excitations in Black Phosphorus.
abstract: We report on the energy- and momentum-resolved optical response of black phosphorus (BP) in its bulk form. Along the armchair direction of the puckered layers, we find a highly dispersive mode that is strongly suppressed in the perpendicular (zigzag) direction. This mode emerges out of the single-particle continuum for finite values of momentum and is therefore interpreted as an exciton. We argue that this exciton, which has already been predicted theoretically for phosphorene-the monolayer form of BP-can be detected by conventional optical spectroscopy in the two-dimensional case and might pave the way for optoelectronic applications of this emerging material.
authors.affiliation: IFW Dresden, Institute for Solid State Research, P.O. Box 270116, D-01171 Dresden, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Schuster
authors.affiliation: IFW Dresden, Institute for Solid State Research, P.O. Box 270116, D-01171 Dresden, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Trinckauf
authors.affiliation: IFW Dresden, Institute for Solid State Research, P.O. Box 270116, D-01171 Dresden, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Habenicht
authors.affiliation: IFW Dresden, Institute for Solid State Research, P.O. Box 270116, D-01171 Dresden, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Knupfer
authors.affiliation: IFW Dresden, Institute for Solid State Research, P.O. Box 270116, D-01171 Dresden, Germany.|Department of Physics, Technische Universität Dresden, 01062 Dresden, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Büchner