1,950 research outputs found
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
Theory of temperature fluctuation statistics in superconductor-normal metal tunnel structures
We describe the statistics of temperature fluctuations in a SINIS structure,
where a normal metal island (N) is coupled by tunnel junctions (I) to two
superconducting leads (S). We specify conditions under which this structure
exhibits manifestly non-Gaussian fluctuations of temperature. We consider both
the Gaussian and non-Gaussian regimes of these fluctuations, and the current
fluctuations that are caused by the fluctuating temperature. We also describe a
measurement setup that could be used to observe the temperature fluctuations.Comment: 10 pages, 9 figures, final versio
Fully Overheated Single-Electron Transistor
We consider the fully overheated single-electron transistor, where the heat
balance is determined entirely by electron transfers. We find three distinct
transport regimes corresponding to cotunneling, single-electron tunneling, and
a competition between the two. We find an anomalous sensitivity to temperature
fluctuations at the crossover between the two latter regimes that manifests in
an exceptionally large Fano factor of current noise.Comment: 6 pages, 3 figures, includes Appendi
Charge transport in ballistic multiprobe graphene structures
We study the the transport properties of multiterminal ballistic graphene
samples, concentrating on the conductance matrix, fluctuations and
cross-correlations. Far away from Dirac point, the current is carried mostly by
propagating modes and the results can be explained with the conventional
semiclassical picture familiar from ray optics, where electrons propagate along
a single direction before scattering or reaching the terminals. However, close
to the Dirac point the transport is due to evanescent modes which do not have
to follow a rectilinear path. As we show in this Letter, this property of the
evanescent modes influences the conductance matrix. However, at best it can be
observed by measuring the cross correlations in an exchange Hanbury Brown-Twiss
experiment.Comment: 5 pages, 5 figure
The association of adolescent fitness with cardiometabolic diseases in late adulthood: A 45-year longitudinal study
This work was supported by Emil Aaltonen Foundation
under Grant 210097 O, Ellen ja Artturi Nyyssönen
Foundation, and Juho Vainio Foundation under Grant
202300290.Objectives: The aim of this study was to examine the associations of adolescent
cardiorespiratory fitness (CRF), muscular fitness (MF), and speed-agility fitness
(SA) with middle-aged cardiometabolic disease risk and explore sex differences.
Methods: This 45-year prospective cohort study examined the associations be-
tween objectively measured fitness at adolescence (12–19 years) and physician-
ascertained diabetes mellitus, elevated blood pressure (BP), and coronary heart
disease reported either in early (37–44 years) or late (57–64 years) middle age, and
self-measurement of waist circumference (WC) in late middle age. Fitness meas-
urements for healthy adolescents in baseline included CRF (1.5 km [girls] and
2 km [boys] run), MF (standing broad jump, sit-ups, pull-ups [boys], and flexed-
arm hang [girls]), and SA (50 m dash and 4 × 10 m shuttle run). Logistic regression
and general linear models were adjusted for baseline age, sex, and body mass
index (BMI), involving data from baseline and at least one follow-up measure-
ment (N up to 1358, 47% males).
Results: Adolescent CRF was inversely, and regardless of adiposity, associ-
ated with middle age accumulated burden of cardiometabolic conditions in the
whole sample (N = 562, ß = −0.10, 95% confidence intervals [CI] [−0.18, −0.03],
p = 0.006), and elevated BP in females (N = 256, OR = 0.71, 95% CI [0.51, 0.91]).
Overall, we observed stronger associations in females than in males. An inverse
association of adolescent MF and SA with middle-aged WC was observed, but it
did not show as consistent associations as with CRF.
Conclusions: In this study, adolescent fitness, particularly CRF, was inversely as-
sociated with the burden of cardiometabolic conditions up to 45 years. Promotion
of fitness in youth may be beneficial in preventing adulthood cardiometabolic
diseases.Emil Aaltonen Foundation 210097 OEllen ja Artturi Nyyssönen
FoundationJuho Vainio Foundation
20230029
Giant current fluctuations in an overheated single electron transistor
Interplay of cotunneling and single-electron tunneling in a thermally
isolated single-electron transistor (SET) leads to peculiar overheating
effects. In particular, there is an interesting crossover interval where the
competition between cotunneling and single-electron tunneling changes to the
dominance of the latter. In this interval, the current exhibits anomalous
sensitivity to the effective electron temperature of the transistor island and
its fluctuations. We present a detailed study of the current and temperature
fluctuations at this interesting point. The methods implemented allow for a
complete characterization of the distribution of the fluctuating quantities,
well beyond the Gaussian approximation. We reveal and explore the parameter
range where, for sufficiently small transistor islands, the current
fluctuations become gigantic. In this regime, the optimal value of the current,
its expectation value, and its standard deviation differ from each other by
parametrically large factors. This situation is unique for transport in
nanostructures and for electron transport in general. The origin of this
spectacular effect is the exponential sensitivity of the current to the
fluctuating effective temperature.Comment: 10 pages, 11 figure
Nonequilibrium characteristics in all-superconducting tunnel structures
We study the nonequilibrium characteristics of superconducting tunnel
structures in the case when one of the superconductors is a small island
confined between large superconductors. The state of this island can be probed
for example via the supercurrent flowing through it. We study both the
far-from-equilibrium limit when the rate of injection for the electrons into
the island exceeds the energy relaxation inside it, and the quasiequilibrium
limit when the electrons equilibrate between themselves. We also address the
crossover between these limits employing the collision integral derived for the
superconducting case. The clearest signatures of the nonequilibrium limit are
the anomalous heating effects seen as a supercurrent suppression at low
voltages, and the hysteresis at voltages close to the gap edge ,
resulting from the peculiar form of the nonequilibrium distribution function.Comment: 8 pages, 10 figure
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