Publications (4)3.85 Total impact
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ABSTRACT: Tunneling conductance at zero voltage in diffusive normal metal (DN)/insulator/swave superconductor junctions is calculated for various situations based on the quasiclassical (QC) theory. In QC theory, the generalized boundary condition introduced by Nazarov [Superlattices and Microstructures 25 1221 (1999)] is applied, where ballistic theory by Blonder Tinkham and Klapwijk and diffusive theory by Volkov Zaitsev and Klapwijk based on the boundary condition by Kupriyanov and Lukichev are naturally reproduced. It is shown that with the increase of the magnitude of resistance of DN (RD), normalized tunneling conductance is enhanced (suppressed) for low (high) transparent barrier. When the length of DN is larger than that of localization length, tunneling conductance obtained by numerical simulation deviates from that by QC theory.  [Show abstract] [Hide abstract]
ABSTRACT: We calculate tunnel conductance for disordered normal metal/unconventional superconductor junctions where superconducting order parameter has broken time reversal symmetry (BTRS), i.e., dx2−y2+is. It is shown that reflectionless tunneling phenomena appears since zeroenergy resonant states caused by the internal phase of dx2−y2pair potential is broken by BTRS states. It is also shown that splitting of zero bias conductance peak due to BTRS in conductance spectra remains whereas the height of the peak is suppressed by the randomness.  [Show abstract] [Hide abstract]
ABSTRACT: Effects of impurity scattering on tunneling conductance in dirty normalmetal/insulator/superconductor junctions are studied based on the Kubo formula and the recursive Green function method. The zerobias conductance peak (ZBCP) is a consequence of the unconventional pairing symmetry in superconductors. The impurity scattering in normal metals suppresses the amplitude of the ZBCP. The degree of the suppression agrees well with results of the quasiclassical Green function theory. When superconductors have $d$+iswave pairing symmetry, the timereversal symmetry is broken in superconductors and the ZBCP splits into two peaks. The random impurity scattering reduces the height of the two splitting peaks. The position of the splitting peaks, however, almost remains unchanged even in the presence of the strong impurity scattering. Thus the two splitting peaks never merge into a single ZBCP. Comment: 12 pages, 5 figures, using jpsj2.cls and overcite.sty  [Show abstract] [Hide abstract]
ABSTRACT: We numerically calculate the tunnel conductance in N/I/D(pi/4) junctions in the presence of randomness in N part, where N, I, D(pi/4) are normal metals, insulators and dwave superconductors with the orientation angle being pi/4, respectively. When N are in the diffusive regime, the zerobias conductance peak (ZBCP) in conductance spectra of N/I/D(pi/4) junctions still can be observed. The height of the ZBCP, however, is suppressed and the shape of the ZBCP is broadened. When N are in the localization regime, the ZBCP tends to split into two peaks.
Publication Stats
8  Citations  
3.85  Total Impact Points  
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Institutions

2003

Nagoya University
 Department of Quantum Engineering
Nagoya, Aichi, Japan
