Direct measurement of sub-Kelvin thermal relaxation rate in nanostructures

Direct measurement of sub-Kelvin thermal relaxation rate in nanostructures
I. J. Maasilta, L. J. Taskinen, and J. T. Karvonen
Nanoscience Center, Department of Physics, FIN-40014 University of Jyväskylä, Finland
The rate at which energy is dissipated at sub-Kelvin temperatures from a nanoscale sample is a critical
factor determining the performance of ultrasensitive bolometers and calorimeters. Also, understanding
the on-chip dissipation mechanisms for manipulation of quantum states (quantum computing etc.) is
critical for succesful ”quantum engineering”. Here, we present a general measurement scheme that can
be used to directly measure the thermal relaxation rate for various systems. As examples, we theoretically
consider the cases where a normal metal sample dissipates either by (i) electron-phonon coupling, (ii)
by quasiparticle diffusion through a NS interface, (iii) by direct electronic diffusion into leads, and (iv)
by radiating photons into the leads. Experimental results for the electron-phonon rate, using SINISjunctions for thermometry, are also presented. The experiments clearly demonstrate the validity of the
approach, and confirm our results on the weakening of the e-p coupling for disordered thin films.
Sorting category: De Conducting electrons in condensed matter
Keywords: thermal relaxation, SINIS-junctions, electron-phonon interaction