Terahertz acoustic phonon Cerenkov emission in bilayer graphene

Abstract

We present a theoretical investigation on the generation of Cerenkov emission of terahertz acoustic phonons in bilayer graphene (BLG) in the presence of a driving dc electric field. We have numerically and analytically studied the Cerenkov phonon emission spectrum, [Formula: see text], and phonon intensity, [Formula: see text], dependence on the phonon frequency [Formula: see text], drift velocity [Formula: see text], electron temperature [Formula: see text], concentration n, and phonon emission angle [Formula: see text] in BLG with and without considering the chirality of the charge carriers. We find that the magnitude of [Formula: see text] increases at larger drift velocities and applied electric fields with the peak of the spectrum shifting toward the higher frequency side. The spectrum magnitude in BLG is found to be much enhanced as compared to conventional 2D semiconductors and transition metal dichalcogenides, which makes it viable for SASER and other practical device applications. The chiral nature of carriers strongly influences the [Formula: see text] behavior and sharpens the spectrum peak but with a decrease in the magnitude. The chirality favors the negative emission spectrum caused by the absorption of acoustic phonons. [Formula: see text] and [Formula: see text] are found to be strongly dependent on temperature but independent of carrier concentration in the equipartition regime. The study is significant from the point of application of BLG as an acousto/optoelectronic device and high-frequency phonon spectrometers.

Flexural and acoustic phonon-drag thermopower and electron energy loss rate in silicene

“…In low dimensional sp 2 hybridized materials like graphene and silicene, phonon scattering is essential for the knowledge of carrier transport phenomena that anticipate the amplification of thermopower. The S p has been investigated a lot in graphene samples [19,22,26,[30][31][32] but remains untouched in silicene so far.…”

“…This area of study has been a significant focus, both theoretically and experimentally. The electron-phonon interaction in single and bilayer graphene has been extensively investigated [20][21][22][23][24][25][26][27][28][29][30][31][32][33] and has proven useful in the fabrication of devices using twodimensional materials on suitable substrates [34][35][36][37][38][39][40][41][42][43]. In the absence of extrinsic sources of scattering, such as impurities, defects, interface roughness, and disorders, transport properties in novel two-dimensional materials are primarily affected by lattice vibrations.…”

“…In the absence of extrinsic sources of scattering, such as impurities, defects, interface roughness, and disorders, transport properties in novel two-dimensional materials are primarily affected by lattice vibrations. Lattice vibrations not only act as intrinsic scattering sources but also become the dominant source of resistivity, particularly around room temperature, and become more significant with an increase in lattice temperature [19][20][21][22][23][24][25][26][27][28][29]. These properties offer exciting possibilities for diverse engineering nanodevices.…”