247 research outputs found
Josephson Effect due to Odd-Frequency Pairs in Diffusive Half Metals
Motivated by a recent experiment [Keizer et al., Nature (London) 439, 825 (2006)], we study the Josephson effect in superconductor/diffusive half metal/superconductor junctions using the recursive Green function method. The spin-flip scattering at the junction interfaces opens the Josephson channel of the odd-frequency spin-triplet Cooper pairs. As a consequence, the local density of states in a half metal has a large peak at the Fermi energy. Therefore the odd-frequency pairs can be detected experimentally by using the scanning tunneling spectroscopy
Quasiparticle Dissipation in d-wave Superconductor Phase Qubit
Recent phase sensitive experiments on high Tc superconductors, e.g.,
YBa_2Cu_3O_7 single crystals, have established the d-wave nature of the cuprate
materials. Here we discuss how to make use of d-wave Josephson junctions in the
construction of a phase qubit. We especially focus on the effect of
quasiparticle dissipation on the macroscopic quantum tunneling which
corresponds to the measurement process for the d-wave phase qubit.Comment: 3 pages, 1 figure, The Seventh International Conference on Quantum
Communication, Measurement and Computing, Glasgow, UK, from 25th to 29th July
2004. To appear in the AIP Conference Proceeding
Electron transport in a ferromagnet-superconductor junction on graphene
In a usual ferromagnet connected with a superconductor, the exchange potential suppresses the superconducting pairing correlation. We show that this common knowledge does not hold in a ferromagnetsuperconductor junction on a graphene. When the chemical potential of a graphene is close to the conical point of energy dispersion, the exchange potential rather assists the charge transport through a junction interface. The loose-bottomed electric structure causes this unusual effec
Quantization of Conductance Minimum and Index Theorem
We discuss the minimum value of the zero-bias differential conductance
in a junction consisting of a normal metal and a nodal
superconductor preserving time-reversal symmetry. Using the quasiclassical
Green function method, we show that is quantized at in the limit of strong impurity scatterings in the
normal metal. The integer represents the number of perfect
transmission channels through the junction. An analysis of the chiral symmetry
of the Hamiltonian indicates that corresponds to the
Atiyah-Singer index in mathematics.Comment: 5 pages, 1 figur
Effects of the phase coherence on the local density of states in superconducting proximity structures
We theoretically study the local density of states in superconducting
proximity structure where two superconducting terminals are attached to a side
surface of a normal-metal wire. Using the quasiclassical Green's function
method, the energy spectrum is obtained for both of spin-singlet -wave and
spin-triplet -wave junctions. In both of the cases, the decay length of the
proximity effect at the zero temperature is limited by a depairing effect due
to inelastic scatterings. In addition to the depairing effect, in -wave
junctions, the decay length depends sensitively on the transparency at the
junction interfaces, which is a unique property to odd-parity superconductors
where the anomalous proximity effect occurs.Comment: 11 pages, 9 figure
Conductance Spectroscopy of Spin-triplet Superconductors
We propose a novel experiment to identify the symmetry of superconductivity
on the basis of theoretical results for differential conductance of a normal
metal connected to a superconductor. The proximity effect from the
superconductor modifies the conductance of the remote current depending
remarkably on the pairing symmetry: spin-singlet or spin-triplet. The clear-cut
difference in the conductance is explained by symmetry of Cooper pairs in a
normal metal with respect to frequency. In the spin-triplet case, the anomalous
transport is realized due to an odd-frequency symmetry of Cooper pairs.Comment: 4pages, 3 figures embedde
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