1,888 research outputs found
Supercurrent-induced temperature gradient across a nonequilibrium SNS Josephson junction
Using tunneling spectroscopy, we have measured the local electron energy
distribution function in the normal part of a superconductor-normal
metal-superconductor (SNS) Josephson junction containing an extra lead to a
normal reservoir. In the presence of simultaneous supercurrent and injected
quasiparticle current, the distribution function exhibits a sharp feature at
very low energy. The feature is odd in energy, and odd under reversal of either
the supercurrent or the quasiparticle current direction. The feature represents
an effective temperature gradient across the SNS Josephson junction that is
controllable by the supercurrent.Comment: 4 pages, 4 figures, corrected typos, added plot to figure
Tunneling into Nonequilibrium Luttinger Liquid with Impurity
We evaluate tunneling rates into/from a voltage biased quantum wire
containing weak backscattering defect. Interacting electrons in such a wire
form a true nonequilibrium state of the Luttinger liquid (LL). This state is
created due to inelastic electron backscattering leading to the emission of
nonequilibrium plasmons with typical frequency . The
tunneling rates are split into two edges. The tunneling exponent at the Fermi
edge is positive and equals that of the equilibrium LL, while the exponent at
the side edge is negative if Coulomb interaction is not too strong.Comment: 4+ pages, 5 figure
Rf-induced transport of Cooper pairs in superconducting single electron transistors in a dissipative environment
We investigate low-temperature and low-voltage-bias charge transport in a
superconducting Al single electron transistor in a dissipating environment,
realized as on-chip high-ohmic Cr microstrips. In our samples with relatively
large charging energy values Ec > EJ, where EJ is the energy of the Josephson
coupling, two transport mechanisms were found to be dominating, both based on
discrete tunneling of individual Cooper pairs: Depending on the gate voltage
Vg, either sequential tunneling of pairs via the transistor island (in the open
state of the transistor around the points Qg = CgVg = e mod(2e), where Cg is
the gate capacitance) or their cotunneling through the transistor (for Qg away
of these points) was found to prevail in the net current. As the open states of
our transistors had been found to be unstable with respect to quasiparticle
poisoning, high-frequency gate cycling (at f ~ 1 MHz) was applied to study the
sequential tunneling mechanism. A simple model based on the master equation was
found to be in a good agreement with the experimental data.Comment: 8 pages, 6 figure
Structural and Magnetic Dynamics in the Magnetic Shape Memory Alloy NiMnGa
Magnetic shape memory Heusler alloys are multiferroics stabilized by the
correlations between electronic, magnetic and structural order. To study these
correlations we use time resolved x-ray diffraction and magneto-optical Kerr
effect experiments to measure the laser induced dynamics in a Heusler alloy
NiMnGa film and reveal a set of timescales intrinsic to the system. We
observe a coherent phonon which we identify as the amplitudon of the modulated
structure and an ultrafast phase transition leading to a quenching of the
incommensurate modulation within 300~fs with a recovery time of a few ps. The
thermally driven martensitic transition to the high temperature cubic phase
proceeds via nucleation within a few ps and domain growth limited by the speed
of sound. The demagnetization time is 320~fs, which is comparable to the
quenching of the structural modulation.Comment: 5 pages, 3 figures. Supplementary materials 5 pages, 5 figure
Single-electron transistor effect in a two-terminal structure
A peculiarity of the single-electron transistor effect makes it possible to
observe this effect even in structures lacking a gate electrode altogether. The
proposed method can be useful for experimental study of charging effects in
structures with an extremely small central island confined between tunnel
barriers like a nanometer-sized quantum dot or a macromolecule probed with a
tunneling microscope), where it is impossible to provide a gate electrode for
control of the tunnel current.Comment: 5 pages, 2 figure
Learning on the move: exploring work with vulnerable young men through the lens of movement
This paper discusses a practice context in which process and movement are central to the provision of care and support. It draws on data from a research project conducted with The Menâs Room, Manchester, England which used ethnographic and mobile methods to explore the complex task staff undertake in engaging and supporting highly vulnerable young men. The organisationâs commitment to getting alongside these young men includes a mobile and highly improvised use of temporary city centre spaces for delivering its work. In this paper, I argue that these movements of practice are not simply a logistical necessity or a physical activity, but involve a kinetic way of attending, reflecting, thinking and knowing in which the organisationâs movements are intrinsic to the provision of care and support
Correlated sequential tunneling through a double barrier for interacting one-dimensional electrons
The problem of resonant tunneling through a quantum dot weakly coupled to
spinless Tomonaga-Luttinger liquids has been studied. We compute the linear
conductance due to sequential tunneling processes upon employing a master
equation approach. Besides the previously used lowest-order golden rule rates
describing uncorrelated sequential tunneling (UST) processes, we systematically
include higher-order correlated sequential tunneling (CST) diagrams within the
standard Weisskopf-Wigner approximation. We provide estimates for the parameter
regions where CST effects can be important. Focusing mainly on the temperature
dependence of the peak conductance, we discuss the relation of these findings
to previous theoretical and experimental results.Comment: replaced with the published versio
Ultrafast relaxation dynamics of the antiferrodistortive phase in Ca doped SrTiO3
The ultrafast dynamics of the octahedral rotation in Ca:SrTiO3 is studied by
time resolved x-ray diffraction after photo excitation over the band gap. By
monitoring the diffraction intensity of a superlattice reflection that is
directly related to the structural order parameter of the soft-mode driven
antiferrodistortive phase in Ca:SrTiO3, we observe a ultrafast relaxation on a
0.2 ps timescale of the rotation of the oxygen octahedron, which is found to be
independent of the initial temperaure despite large changes in the
corresponding soft-mode frequency. A further, much smaller reduction on a
slower picosecond timescale is attributed to thermal effects. Time-dependent
density-functional-theory calculations show that the fast response can be
ascribed to an ultrafast displacive modification of the soft-mode potential
towards the normal state, induced by holes created in the oxygen 2p states
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