1,261 research outputs found
Direct observation of vortices in an array of holes at low temperature: temperature dependance and first visualization of localized superconductivity
A scanning micro superconducting quantum interference device (microSQUID)
microscope is used to directly image vortices in a superconducting Al thin
film. We observe the temperature dependence of the vortex distribution in a
regular defect (hole) array patterned into the Al film. The first direct
observation of the localized superconducting state around the holes is shown as
well as the effect of the hole size on nucleation of the superconducting state
Conductance statistics in small insulating GaAs:Si wires at low temperature. II. Experimental study
We have observed reproducible conductance fluctuations at low temperature in
a small GaAs:Si wire driven across the Anderson transition by the application
of a gate voltage. We analyse quantitatively the log-normal conductance
statistics in terms of truncated quantum fluctuations. Quantum fluctuations due
to small changes of the electron energy (controlled by the gate voltage) cannot
develop fully due to identified geometrical fluctuations of the resistor
network describing the hopping through the sample.
The evolution of the fluctuations versus electron energy and magnetic field
shows that the fluctuations are non-ergodic, except in the critical insulating
region of the Anderson transition, where the localization length is larger than
the distance between Si impurities.
The mean magnetoconductance is in good accordance with simulations based on
the Forward-Directed-Paths analysis, i.e. it saturates to as decreases over orders of
magnitude in the strongly localized regime.Comment: Email contact: [email protected]
Nonlinear Convection in Reaction-diffusion Equations under dynamical boundary conditions
We investigate blow-up phenomena for positive solutions of nonlinear
reaction-diffusion equations including a nonlinear convection term in a bounded domain of
under the dissipative dynamical boundary conditions . Some conditions on and are discussed
to state if the positive solutions blow up in finite time or not. Moreover, for
certain classes of nonlinearities, an upper-bound for the blow-up time can be
derived and the blow-up rate can be determinated.Comment: 20 page
Scanning microSQUID Force Microscope
A novel scanning probe technique is presented: Scanning microSQUID Force
microscopy (SSFM). The instrument features independent topographic and magnetic
imaging. The SSFM operates in a dilution refrigerator in cryogenic vacuum.
Sample and probe can be cooled to 0.45 K. The probe consists of a microSQUID
placed at the edge of a silicon chip attached to a quartz tuning fork. A
topographic vertical resolution of 0.02 micrometer is demonstrated and magnetic
flux as weak as is resolved with a 1 micrometer diameter
microSQUID loop.Comment: submitted to Review of Scientific Instrument
Study of First-Order Thermal Sigma-Delta Architecture for Convective Accelerometers
This paper presents the study of an original closed-loop conditioning
approach for fully-integrated convective inertial sensors. The method is
applied to an accelerometer manufactured on a standard CMOS technology using an
auto-aligned bulk etching step. Using the thermal behavior of the sensor as a
summing function, a first order sigma-delta modulator is built. This
"electro-physical" modulator realizes an analog-to-digital conversion of the
signal. Besides the feedback scheme should improve the sensor performance.Comment: Submitted on behalf of EDA Publishing Association
(http://irevues.inist.fr/handle/2042/16838
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