title: In-Plane Optical Anisotropy of Layered Gallium Telluride.
abstract: Layered gallium telluride (GaTe) has attracted much attention recently, due to its extremely high photoresponsivity, short response time, and promising thermoelectric performance. Different from most commonly studied two-dimensional (2D) materials, GaTe has in-plane anisotropy and a low symmetry with the C2h(3) space group. Investigating the in-plane optical anisotropy, including the electron-photon and electron-phonon interactions of GaTe is essential in realizing its applications in optoelectronics and thermoelectrics. In this work, the anisotropic light-matter interactions in the low-symmetry material GaTe are studied using anisotropic optical extinction and Raman spectroscopies as probes. Our polarized optical extinction spectroscopy reveals the weak anisotropy in optical extinction spectra for visible light of multilayer GaTe. Polarized Raman spectroscopy proves to be sensitive to the crystalline orientation of GaTe, and shows the intricate dependences of Raman anisotropy on flake thickness, photon and phonon energies. Such intricate dependences can be explained by theoretical analyses employing first-principles calculations and group theory. These studies are a crucial step toward the applications of GaTe especially in optoelectronics and thermoelectrics, and provide a general methodology for the study of the anisotropy of light-matter interactions in 2D layered materials with in-plane anisotropy.
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: Yuki
authors.initials: Y
authors.lastname: Tatsumi
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: College of Sciences, Liaoning Shihua University , Fushun 113001, China.
authors.forename: Huaihong
authors.initials: H
authors.lastname: Guo
authors.affiliation: Department of Nuclear Science and Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Ziqiang
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Department of Physics, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Garrett
authors.initials: G
authors.lastname: Watson
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Puretzky
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
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 Nuclear Science and Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Ju
authors.initials: J
authors.lastname: Li
authors.affiliation: Department of Physics, Tohoku University , Sendai 980-8578, Japan.|Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences , Shenyang 110016, China.
authors.forename: Teng
authors.initials: T
authors.lastname: Yang
authors.affiliation: Department of Physics, Tohoku University , Sendai 980-8578, Japan.
authors.forename: Riichiro
authors.initials: R
authors.lastname: Saito
authors.affiliation: Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.|Department of Physics, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Mildred S
authors.initials: MS
authors.lastname: Dresselhaus
keywords: electron−photon interaction; group theory; light-matter interaction; optical transition selection rules; polarization-dependent Raman spectroscopy; polarization-dependent optical extinction