4,225 research outputs found
Nonlinear transport theory for hybrid normal-superconducting devices
We report a theory for analyzing nonlinear DC transport properties of
mesoscopic or nanoscopic normal-superconducting (N-S) systems. Special
attention was paid such that our theory satisfies gauge invariance. At the
linear transport regime and the sub-gap region where the familiar scattering
matrix theory has been developed, we provide confirmation that our theory and
the scattering matrix theory are equivalent. At the nonlinear regime, however,
our theory allows the investigation of a number of important problems: for N-S
hybrid systems we have derived the general nonlinear current-voltage
characteristics in terms of the scattering Green's function, the second order
nonlinear conductance at the weakly nonlinear regime, and nonequilibrium charge
pile-up in the device which defines the electrochemical capacitance
coefficients
Experimental Trapped-ion Quantum Simulation of the Kibble-Zurek dynamics in momentum space
The Kibble-Zurek mechanism is the paradigm to account for the nonadiabatic
dynamics of a system across a continuous phase transition. Its study in the
quantum regime is hindered by the requisite of ground state cooling. We report
the experimental quantum simulation of critical dynamics in the
transverse-field Ising model by a set of Landau-Zener crossings in
pseudo-momentum space, that can be probed with high accuracy using a single
trapped ion. We test the Kibble-Zurek mechanism in the quantum regime in the
momentum space and find the measured scaling of excitations is in accordance
with the theoretical prediction.Comment: 10 pages, 3 figures Published in Scientific Reports,
http://www.nature.com/articles/srep3338
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