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Title: Cerenkov emission of acoustic phonons electrically generated from three-dimensional Dirac semimetals

Abstract

Cerenkov acoustic phonon emission is theoretically investigated in a three-dimensional Dirac semimetal (3DDS) when it is driven by a dc electric field E. Numerical calculations are made for Cd{sub 3}As{sub 2} in which mobility and electron concentration are large. We find that Cerenkov emission of acoustic phonons takes place when the electron drift velocity v{sub d} is greater than the sound velocity v{sub s}. This occurs at small E (∼few V/cm) due to large mobility. Frequency (ω{sub q}) and angular (θ) distribution of phonon emission spectrum P(ω{sub q}, θ) are studied for different electron drift velocities v{sub d} (i.e., different E) and electron concentrations n{sub e}. The frequency dependence of P(ω{sub q}, θ) shows a maximum P{sub m}(ω{sub q}, θ) at about ω{sub m} ≈ 1 THz and is found to increase with the increasing v{sub d} and n{sub e}. The value of ω{sub m} shifts to higher region for larger n{sub e}. It is found that ω{sub m}/n{sub e}{sup 1/3} and P{sub m}(ω{sub q}, θ)/n{sub e}{sup 2/3} are nearly constants. The latter is in contrast with the P{sub m}(ω{sub q}, θ)n{sub e}{sup 1/2 }= constant in conventional bulk semiconductor. Each maximum is followed by a vanishing spectrum at nearly “2k{sub f} cutoff,” wheremore » k{sub f} is the Fermi wave vector. Angular dependence of P(ω{sub q}, θ) and the intensity P(θ) of the phonon emission shows a maximum at an emission angle 45° and is found to increase with increasing v{sub d}. P(θ) is found to increase linearly with n{sub e} giving the ratio P(θ)/(n{sub e}v{sub d}) nearly a constant. We suggest that it is possible to have the controlled Cerenkov emission and generation of acoustic phonons with the proper choice of E, θ, and n{sub e}. 3DDS with large n{sub e} and mobility can be a good source of acoustic phonon generation in ∼THz regime.« less

Authors:
 [1]
  1. Department of Physics, Karnatak University, Dharwad 580 003, Karnataka (India)
Publication Date:
OSTI Identifier:
22596999
Resource Type:
Journal Article
Journal Name:
Journal of Applied Physics
Additional Journal Information:
Journal Volume: 119; Journal Issue: 19; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0021-8979
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; CADMIUM ARSENIDES; CHERENKOV RADIATION; CONCENTRATION RATIO; ELECTRIC FIELDS; ELECTRON DRIFT; ELECTRONS; EMISSION; EMISSION SPECTRA; FREQUENCY DEPENDENCE; MOBILITY; NUMERICAL ANALYSIS; PHONONS; SEMICONDUCTOR MATERIALS; SEMIMETALS; SOUND WAVES; THREE-DIMENSIONAL CALCULATIONS; VELOCITY

Citation Formats

Kubakaddi, S. S., E-mail: sskubakaddi@gmail.com. Cerenkov emission of acoustic phonons electrically generated from three-dimensional Dirac semimetals. United States: N. p., 2016. Web. doi:10.1063/1.4949753.
Kubakaddi, S. S., E-mail: sskubakaddi@gmail.com. Cerenkov emission of acoustic phonons electrically generated from three-dimensional Dirac semimetals. United States. https://doi.org/10.1063/1.4949753
Kubakaddi, S. S., E-mail: sskubakaddi@gmail.com. 2016. "Cerenkov emission of acoustic phonons electrically generated from three-dimensional Dirac semimetals". United States. https://doi.org/10.1063/1.4949753.
@article{osti_22596999,
title = {Cerenkov emission of acoustic phonons electrically generated from three-dimensional Dirac semimetals},
author = {Kubakaddi, S. S., E-mail: sskubakaddi@gmail.com},
abstractNote = {Cerenkov acoustic phonon emission is theoretically investigated in a three-dimensional Dirac semimetal (3DDS) when it is driven by a dc electric field E. Numerical calculations are made for Cd{sub 3}As{sub 2} in which mobility and electron concentration are large. We find that Cerenkov emission of acoustic phonons takes place when the electron drift velocity v{sub d} is greater than the sound velocity v{sub s}. This occurs at small E (∼few V/cm) due to large mobility. Frequency (ω{sub q}) and angular (θ) distribution of phonon emission spectrum P(ω{sub q}, θ) are studied for different electron drift velocities v{sub d} (i.e., different E) and electron concentrations n{sub e}. The frequency dependence of P(ω{sub q}, θ) shows a maximum P{sub m}(ω{sub q}, θ) at about ω{sub m} ≈ 1 THz and is found to increase with the increasing v{sub d} and n{sub e}. The value of ω{sub m} shifts to higher region for larger n{sub e}. It is found that ω{sub m}/n{sub e}{sup 1/3} and P{sub m}(ω{sub q}, θ)/n{sub e}{sup 2/3} are nearly constants. The latter is in contrast with the P{sub m}(ω{sub q}, θ)n{sub e}{sup 1/2 }= constant in conventional bulk semiconductor. Each maximum is followed by a vanishing spectrum at nearly “2k{sub f} cutoff,” where k{sub f} is the Fermi wave vector. Angular dependence of P(ω{sub q}, θ) and the intensity P(θ) of the phonon emission shows a maximum at an emission angle 45° and is found to increase with increasing v{sub d}. P(θ) is found to increase linearly with n{sub e} giving the ratio P(θ)/(n{sub e}v{sub d}) nearly a constant. We suggest that it is possible to have the controlled Cerenkov emission and generation of acoustic phonons with the proper choice of E, θ, and n{sub e}. 3DDS with large n{sub e} and mobility can be a good source of acoustic phonon generation in ∼THz regime.},
doi = {10.1063/1.4949753},
url = {https://www.osti.gov/biblio/22596999}, journal = {Journal of Applied Physics},
issn = {0021-8979},
number = 19,
volume = 119,
place = {United States},
year = {Sat May 21 00:00:00 EDT 2016},
month = {Sat May 21 00:00:00 EDT 2016}
}