Electron cooling in three‐dimensional Dirac fermion systems at low temperature: Effect of screening

Hot electron cooling rate P , due to acoustic phonons, is investigated in three‐dimensional Dirac fermion systems at low temperature taking account of the screening of electron–acoustic phonon interaction. P is studied as a function of electron temperature T e and electron concentration n e . Screening is found to suppress P very significantly for about T e < 0.5 K and its effect reduces considerably for about T e > 1 K in Cd 3 As 2 . In Bloch–Grüneisen (BG) regime, for screened (unscreened) case the T e dependence is P ∼ T e 9 ( T e 5 ) and the n e dependence gives P ∼ n e –5/3 ( n e –1/3 ). The T e dependence is characteristic of 3D phonons and n e dependence is characteristics of 3D Dirac fermions. The plot of P / T e 4 vs. T e shows a maximum at temperature T em which shifts to higher values for larger n e . Interestingly, the maximum is nearly same for different n e and T em / n e 1/3 being nearly constant. More importantly, we propose, the n e dependent measurements of P would provide a clearer signature to identify 3D Dirac semimetal phase. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)