Modification of electron-phonon coupling by micromachining and suspension

Abstract

Weak electron-phonon interaction in metals at low temperatures forms the basis of operation for cryogenic hot-electron bolometers and calorimeters. Standard power laws, describing the heat flow in the majority of experiments, have been identified and derived theoretically. However, a full picture encompassing experimentally relevant effects such as reduced dimensionality, material interfaces, and disorder is in its infancy, and has not been tested extensively. Here, we study the electron-phonon heat flow in a thin gold film on a SiO 2 platform below 100 mK using supercurrent thermometry. We find the power law exponent to be modified from 5.1 to 4.6 as the platform is micromachined and released from its substrate. We attribute this change to a modified phonon spectrum. The findings are compared to past experiments and theoretical models. arXiv:1910.10126v1 [cond-mat.mes-hall]

Thermal relaxation in metal films limited by diffuson lattice excitations of amorphous substrates

“…For this purpose we use a commercial high electron mobility transistor connected in parallel with the device, that is depleted otherwise. [40], Σ e−ph = 1.85 × 10 9 WK −n m −3 , n = 6, for InO x [41], and extrapolated value of τ e−ph to 10 K (τ e−ph = 9 ps), D = 0.3 cm 2 /s for NbN [42] we calculate l e−ph : 350 nm for Au, 18 nm for NbN at 10 K, and 6.6 nm for InO x at 5 K.…”

Electron-Phonon Interaction in Aluminum SINIS

“…In addition to these dependences, in the literature, one can find other models of electron-phonon relaxation, and powerlaw dependences from T 4 to T 6 , related to the so-called dirty limit with a short electron mean free path. In the case of detachment of the absorber from the substrate, when electrons are considered in a three-dimensional model and absorber phonons in a two-dimensional model, the exponent is 4.54 in 2D limit and n=6…7 in bulk limit [8,9]. In the general case, the thermal conductivity between electrons and phonons is inversely proportional to the electron-phonon relaxation time Gep=C/ep, where the electronic heat capacity is C =vT and  is the Sommerfeld constant.…”