RESUMEN
The potential for thermoelectric applications of two-dimensional materials is quite promising. Usingab-initiocalculations, we have investigated the electronic band structure, phonon band structure, electronic density of states, and phonon density of states of monolayers MoS2, MoSe2, and WS2. In order to compute the thermoelectric properties of monolayers MoS2, MoSe2, and WS2, we used theab-initiomodel suggested by Faghaniniaet al(2015Phys. Rev.B91235123). Within this model, by using inputs from density functional theory and considering all relevant elastic and inelastic scattering mechanisms, we have calculated the thermoelectric properties of monolayers MoS2, MoSe2, and WS2over various ranges of temperature (T) and carrier concentration (n). The obtained results of Seebeck coefficients (S) and figure of merit (ZT) atT= 300 K for bothn/p-types of monolayers MoS2, MoSe2, and WS2are in good agreement with the findings obtained by other models using the Boltzmann transport equation within a constant relaxation time framework.
RESUMEN
We present a theoretical model for the calculation of the energy loss rate (ELR) of hot electrons in a monolayer graphene due to their coupling with acoustic phonons at high perpendicular magnetic fields. Electrons interact with both transverse acoustic (TA) and longitudinal acoustic (LA) phonons. Numerical simulations of the ELR are performed as a function of the magnetic field, the electron temperature, the electron density, and the Landau level broadening. We find robust oscillations of the ELR as a function of the filling factor ν that originate from the oscillating density of states at the Fermi level. Screening effects on the deformation potential coupling are taken into account, and it is found that they lead to a significant reduction of ELR, especially, at low electron temperatures, Te, and high magnetic fields. At temperatures much lower than the Bloch-Grüneisen temperature, the ELR shows a Te4 dependence that is related to the unscreened electron interaction with TA acoustic phonons. Finally, our theoretical model is compared with existing experimental results and a very good quantitative agreement is found.
RESUMEN
A theory of hot electron cooling power due to polar optical phonons P op is developed in 3D Dirac semimetal (3DDS) Cd3As2 taking account of hot phonon effect. Hot phonon distribution N q and P op are investigated as a function of electron temperature T e, electron density n e, and phonon relaxation time [Formula: see text]. It is found that P op increases rapidly (slowly) with T e at lower (higher) temperature regime. Whereas, P op is weakly decreasing with increasing n e. The results are compared with those for three-dimensional electron gas (3DEG) in Cd3As2 semiconductor. Hot phonon effect is found to reduce P op considerably and it is stronger in 3DDS Cd3As2 than in Cd3As2 semiconductor. P op is also compared with the hot electron cooling power due to acoustic phonons P ac. We find that a crossover takes place from P ac dominated cooling at low T e to P op dominated cooling at higher T e. The temperature at which this crossover occurs shifts towards higher values with the increase of n e. Also, hot electron energy relaxation time [Formula: see text] is discussed. It is suggested that [Formula: see text] can be tuned to achieve faster or slower energy loss for suitable applications of Cd3As2.
