3,689 research outputs found
Thermalization of hot electrons via interfacial electron-magnon interaction
Recent work on layered structures of superconductors (S) or normal metals (N)
in contact with ferromagnetic insulators (FI) has shown how the properties of
the previous can be strongly affected by the magnetic proximity effect due to
the static FI magnetization. Here we show that such structures can also exhibit
a new electron thermalization mechanism due to the coupling of electrons with
the dynamic magnetization, i.e., magnons in FI. We here study the heat flow
between the two systems and find that in thin films the heat conductance due to
the interfacial electron-magnon collisions can dominate over the well-known
electron-phonon coupling below a certain characteristic temperature that can be
straightforwardly reached with present-day experiments. We also study the role
of the magnon band gap and the induced spin-splitting field induced in S on the
resulting heat conductance and show that heat balance experiments can reveal
information about such quantities in a way quite different from typical magnon
spectroscopy experiments
Electron-phonon heat transfer in monolayer and bilayer graphene
We calculate the heat transfer between electrons to acoustic and optical
phonons in monolayer and bilayer graphene (MLG and BLG) within the
quasiequilibrium approximation. For acoustic phonons, we show how the
temperature-power laws of the electron-phonon heat current for BLG differ from
those previously derived for MLG and note that the high-temperature
(neutral-regime) power laws for MLG and BLG are also different, with a weaker
dependence on the electronic temperature in the latter. In the general case we
evaluate the heat current numerically. We suggest that a measurement of the
heat current could be used for an experimental determination of the
electron-acoustic phonon coupling constants, which are not accurately known.
However, in a typical experiment heat dissipation by electrons at very low
temperatures is dominated by diffusion, and we estimate the crossover
temperature at which acoustic-phonon coupling takes over in a sample with Joule
heating. At even higher temperatures optical phonons begin to dominate. We
study some examples of potentially relevant types of optical modes, including
in particular the intrinsic in-plane modes, and additionally the remote surface
phonons of a possible dielectric substrate.Comment: 13 pages, 8 figures; moved details to appendixes, added discussion of
remote phonon
Physics of Proximity Josephson Sensor
We study the proximity Josephson sensor (PJS) in both bolometric and
calorimetric operation and optimize it for different temperature ranges between
25 mK and a few Kelvin. We investigate how the radiation power is absorbed in
the sensor and find that the irradiated sensor is typically in a weak
nonequilibrium state. We show in detail how the proximity of the
superconductors affects the device response: for example via changes in
electron-phonon coupling and out-of-equilibrium noise. In addition, we estimate
the applicability of graphene as the absorber material.Comment: 13 pages, 11 figures, submitted to Journal of Applied Physics, v2:
Addition of a new section discussing the radiation coupling to the device,
several minor change
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