title: Anisotropic Electron-Photon and Electron-Phonon Interactions in Black Phosphorus.
abstract: Orthorhombic black phosphorus (BP) and other layered materials, such as gallium telluride (GaTe) and tin selenide (SnSe), stand out among two-dimensional (2D) materials owing to their anisotropic in-plane structure. This anisotropy adds a new dimension to the properties of 2D materials and stimulates the development of angle-resolved photonics and electronics. However, understanding the effect of anisotropy has remained unsatisfactory to date, as shown by a number of inconsistencies in the recent literature. We use angle-resolved absorption and Raman spectroscopies to investigate the role of anisotropy on the electron-photon and electron-phonon interactions in BP. We highlight, both experimentally and theoretically, a nontrivial dependence between anisotropy and flake thickness and photon and phonon energies. We show that once understood, the anisotropic optical absorption appears to be a reliable and simple way to identify the crystalline orientation of BP, which cannot be determined from Raman spectroscopy without the explicit consideration of excitation wavelength and flake thickness, as commonly used previously.
authors.affiliation: Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Xi
authors.initials: X
authors.lastname: Ling
authors.affiliation: Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Shengxi
authors.initials: S
authors.lastname: Huang
authors.affiliation: Department of Physics, Tohoku University , Sendai 980-8578, Japan.
authors.forename: Eddwi H
authors.initials: EH
authors.lastname: Hasdeo
authors.affiliation: Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute , Troy, New York 12180, United States.
authors.forename: Liangbo
authors.initials: L
authors.lastname: Liang
authors.affiliation: Department of Physics and Astronomy, University of Pennsylvania , Philadelphia, Pennsylvania 19104, United States.
authors.forename: William M
authors.initials: WM
authors.lastname: Parkin
authors.affiliation: Department of Physics, Tohoku University , Sendai 980-8578, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Tatsumi
authors.affiliation: Department of Physics, Tohoku University , Sendai 980-8578, Japan.
authors.forename: Ahmad R T
authors.initials: AR
authors.lastname: Nugraha
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Puretzky
authors.affiliation: Department of Physics and Astronomy, University of Pennsylvania , Philadelphia, Pennsylvania 19104, United States.
authors.forename: Paul Masih
authors.initials: PM
authors.lastname: Das
authors.forename: Bobby G
authors.initials: BG
authors.lastname: Sumpter
authors.forename: David B
authors.initials: DB
authors.lastname: Geohegan
authors.affiliation: Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Jing
authors.initials: J
authors.lastname: Kong
authors.affiliation: Department of Physics, Tohoku University , Sendai 980-8578, Japan.
authors.forename: Riichiro
authors.initials: R
authors.lastname: Saito
authors.affiliation: Department of Physics and Astronomy, University of Pennsylvania , Philadelphia, Pennsylvania 19104, United States.
authors.forename: Marija
authors.initials: M
authors.lastname: Drndic
authors.affiliation: Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute , Troy, New York 12180, United States.
authors.forename: Vincent
authors.initials: V
authors.lastname: Meunier
authors.affiliation: Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Mildred S
authors.initials: MS
authors.lastname: Dresselhaus
keywords: In-plane anisotropy; Raman spectroscopy; crystalline orientation; optical absorption; optical selection rule