Conditions of coherent-phonon excitation in SrMnSb2 films and crystals
Abstract
Excitation of coherent phonons has the potential to dramatically alter the electronic structure of Dirac and Weyl semimetals, enabling sub-picosecond control of their optical and electronic properties. The Dirac semimetal SrMnSb2 is a candidate for such control, with a coherent-phonon mode that is predicted to close and reopen a gap at the Dirac node. Here, through a series of ultrafast pump-probe experiments, we establish suitable samples and conditions for driving the coherent phonon to high amplitude and attempting to observe the gap’s closure. Films of SrMnSb2 grown by molecular-beam epitaxy are shown to have phononic properties matching those of bulk crystals. We find that the phonon can be strongly excited by pump pulses with wavelength near 1500 nm, which will excite a 30-nm film almost uniformly and will penetrate the arsenic capping layers that protect the films. We find that samples withstand pump pulses of fluence up to 20 mJ/cm2, and we demonstrate the potential for sequences of pulses to amplify the oscillation while suppressing other phonon modes. Armed with our new knowledge of the conditions for exciting the desired coherent phonon, future experiments will be well prepared to measure its motion and to observe phononic control of the Dirac-point gap.
Article Details
Journal Info
Journal of Applied Physics
American Institute of Physics
Authors (16)
Manita Rai
Department of Physics and Engineering Physics, Santa Clara University 1 , 500 El Camino Real, Santa Clara, California 95053-0315,
Sujan Subedi
Department of Physics, Temple University 2 , Philadelphia, Pennsylvania 19122,
Hannah E. Aguirre
Department of Physics and Engineering Physics, Santa Clara University 1 , 500 El Camino Real, Santa Clara, California 95053-0315,
Hans A. Bechtel
Advanced Light Source Division, Lawrence Berkeley National Laboratory 3 , Berkeley, California 94720,
Renee Chapla
Department of Physics and Engineering Physics, Santa Clara University 1 , 500 El Camino Real, Santa Clara, California 95053-0315,
Javier Garcia de Castro
Department of Physics and Engineering Physics, Santa Clara University 1 , 500 El Camino Real, Santa Clara, California 95053-0315,
Dennis D. Klug
National Research Council Canada 4 , Ottawa, Ontario K1A 0R6,
Jinyu Liu
Madison G. Masten
Department of Physics and Engineering Physics, Santa Clara University 1 , 500 El Camino Real, Santa Clara, California 95053-0315,
Trung Hieu Nguyen
Institute of Theoretical and Applied Research, Duy Tan University 6 , Hanoi 100000,
Thomas J. Rehaag
Department of Physics, University of Warwick 7 , Coventry CV4 7AL,
Yiyi Wang
Zhiqiang Mao
Department of Physics, The Pennsylvania State University, University Park, PA, USA.
Gavin R. Bell
Department of Physics, University of Warwick 7 , Coventry CV4 7AL,
Darius H. Torchinsky
Department of Physics, Temple University 2 , Philadelphia, Pennsylvania 19122,
Chris P. Weber
Department of Physics and Engineering Physics, Santa Clara University 1 , 500 El Camino Real, Santa Clara, California 95053-0315,