11,978 research outputs found
Josephson response of a conventional and a noncentrosymmetric superconductor coupled via a double quantum dot
We consider transport through a Josephson junction consisting of a
conventional s-wave superconductor coupled via a double quantum dot to a
noncentrosymmetric superconductor with both, singlet and triplet pairing. We
calculate the Andreev bound state energies and the associated Josephson
current. We demonstrate that the current-phase relation is a sensitive probe of
the singlet-triplet ratio in the noncentrosymmetric superconductor. In
particular, in the presence of an inhomogeneous magnetic field the system
exhibits a -junction behavior.Comment: 8 pages, 7 figures, published versio
Model for the magnetoresistance and Hall coefficient of inhomogeneous graphene
We show that when bulk graphene breaks into n-type and p-type puddles, the
in-plane resistivity becomes strongly field dependent in the presence of a
perpendicular magnetic field, even if homoge- neous graphene has a
field-independent resistivity. We calculate the longitudinal resistivity
\rho_{xx} and Hall resistivity \rho_{xy} as a function of field for this
system, using the effective-medium approximation. The conductivity tensors of
the individual puddles are calculated using a Boltzmann approach suit- able for
the band structure of graphene near the Dirac points. The resulting resistivity
agrees well with experiment, provided that the relaxation time is weakly
field-dependent. The calculated Hall resistivity has the sign of the majority
carrier and vanishes when there are equal number of n and p type puddles.Comment: 5 pages, 4 figure
Numerical Study of Energy Loss by a Nanomechanical Oscillator Coupled to a Cooper Pair Box
We calculate the dynamics of a nanomechanical oscillator (NMO) coupled
capacitively to a Cooper pair box (CPB), by solving a stochastic Schrodinger
equation with two Lindblad operators. Both the NMO and the CPB are assumed
dissipative, and the coupling is treated within the rotating wave
approximation. We show numerically that, if the CPB decay time is smaller than
the NMO decay time, the coupled NMO will lose energy faster, and the coupled
CPB more slowly, than do the uncoupled NMO and CPB. The results show that the
efficiency of energy loss by an NMO can be substantially increased if the NMO
is coupled to a CPB.Comment: 10 pages, 3 figure
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