Nonlinear optical observation of coherent acoustic Dirac plasmons in thin-film topological insulators.
Low-energy collective electronic excitations exhibiting sound-like linear dispersion have been intensively studied both experimentally and theoretically for a long time. However, coherent acoustic plasmon modes appearing in time-domain measurements are rarely observed due to Landau damping by the single-particle continua. Here we report on the observation of coherent acoustic Dirac plasmon (CADP) modes excited in indirectly (electrostatically) opposite-surface coupled films of the topological insulator Bi2Se3. Using transient second-harmonic generation, a technique capable of independently monitoring the in-plane and out-of-plane electron dynamics in the films, the GHz-range oscillations were observed without corresponding oscillations in the transient reflectivity. These oscillations were assigned to the transverse magnetic and transverse electric guided CADP modes induced by the evanescent guided Lamb acoustic waves and remained Landau undamped due to fermion tunnelling between the opposite-surface Dirac states.
Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia 26506-6315, USA.|Institute of Physics, National Academy of Sciences of Ukraine, Kiev 03028, Ukraine.
Yuri D
YD
Glinka
Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia 26506-6315, USA.
Sercan
S
Babakiray
Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia 26506-6315, USA.
Trent A
TA
Johnson
Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia 26506-6315, USA.
Mikel B
MB
Holcomb
Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia 26506-6315, USA.|Department of Physics, University of California, Santa Cruz, California 90564, USA.
David
D
Lederman
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