19 research outputs found
Influence of Supercurrents on Low-Temperature Thermopower in Mesoscopic N/S Structures
The thermopower of mesoscopic normal metal/superconductor structures has been
measured at low temperatures. Effect of supercurrent present in normal part of
the structure was studied in two cases: when it was created by applied external
magnetic field and when it was applied directly using extra superconducting
electrodes. Temperature and magnetic field dependencies of thermopower are
compared to the numerical simulations based on the quasiclassical theory of the
superconducting proximity effect.Comment: 21 pages, 12 figures. To be published in the proceedings of the ULTI
conference organized in Lammi, Finland (2006
Magnetic field influence on the proximity effect in semiconductor - superconductor hybrid structures and their thermal conductance
We show that a magnetic field can influnce the proximity effect in NS
junctions via diamagnetic screening current flowing in the superconductor.
Using ballistic quasi-one-dimensional (Q1D) electron channels as an example, we
show that the supercurrent flow shifts the proximity-induced minigap in the
excitation spectrum of a Q1D system from the Fermi level to higher
quasiparticle energies. Thermal conductance of a Q1D channel (normalized by
that of a normal Q1D ballistic system) is predicted to manifest such a spectral
feature as a nonmonotonic behavior at temperatures corresponding to the energy
of excitation into the gapful part of the spectrum.Comment: 5 pages, 3 figures, revised version with a new titl
Thermoelectric effects in superconducting proximity structures
Attaching a superconductor in good contact with a normal metal makes rise to
a proximity effect where the superconducting correlations leak into the normal
metal. An additional contact close to the first one makes it possible to carry
a supercurrent through the metal. Forcing this supercurrent flow along with an
additional quasiparticle current from one or many normal-metal reservoirs makes
rise to many interesting effects. The supercurrent can be used to tune the
local energy distribution function of the electrons. This mechanism also leads
to finite thermoelectric effects even in the presence of electron-hole
symmetry. Here we review these effects and discuss to which extent the existing
observations of thermoelectric effects in metallic samples can be explained
through the use of the dirty-limit quasiclassical theory.Comment: 14 pages, 10 figures. 374th WE-Heraus seminar: Spin physics of
superconducting heterostructures, Bad Honnef, 200
Magnetically ordered state at correlated oxide interfaces: the role of random oxygen defects
Using an effective one-band Hubbard model with disorder, we consider magnetic
states of the correlated oxide interfaces, where effective hole self-doping and
a magnetially ordered state emerge due to electronic and ionic reconstructions.
By employing the coherent potential approximation, we analyze the effect of
random oxygen vacancies on the two-dimensional magnetism. We find that the
random vacancies enhance the ferromagnetically ordered state and stabilize a
robust magnetization above a critical vacancy concentration of about c=0.1. In
the strong-correlated regime, we also obtain a nonmonotonic increase of the
magnetization upon an increase of vacancy concentration and a substantial
increase of the magnetic moments, which can be realized at oxygen reduced
high-Tc cuprate interfaces.Comment: 8 pages, 2 figures, submitted to J Supercond Novel Magnetism (ICSM12
conference contribution
Patch clamp technique: Review of the current state of the art and potential contributions from nanoengineering
The patch clamp technique permits high-resolution recording of the ionic currents flowing through a cell's plasma membrane. In different configurations, this technique has allowed experimenters to record and manipulate the currents that flow either through single ion channels or those that flow across the whole plasma membrane. Unfortunately, the conventional patch clamp method is laborious, requiring the careful fabrication of electrodes, skillful manipulation of the patch pipette towards a cell, and the clever design of electronics and apparatus to allow low-noise recordings. Advances in microfabrication offer promising technologies for high-throughput patch clamp recordings, particularly suitable for drug screening. This paper provides a review of the advances that have been made in the patch clamp technique over the years and considers where application of nanotechnology might provide significant contributions in the future