Symmetry conditions of a nodal superconductor for generating robust flat-band Andreev bound states at its dirty surface

We discuss the symmetry property of a nodal superconductor that hosts robust flat-band zero-energy states at its surface under potential disorder. Such robust zero-energy states are known to induce the anomalous proximity effect in a dirty normal metal attached to a superconductor. A recent study has shown that a topological index ${\cal N}_\mathrm{ZES}$ describes the number of zero-energy states at the dirty surface of a $p$-wave superconductor. We generalize the theory to clarify the conditions required for a superconductor that enables ${\cal N}_\mathrm{ZES}\neq 0$. Our results show that ${\cal N}_\mathrm{ZES}\neq 0$ is realized in a topological material that belongs to either the BDI or CII class. We also present two realistic Hamiltonians that result in ${\cal N}_\mathrm{ZES}\neq 0$.Comment: 9 pages, 3 figure

Fano Resonance in a Quantum Wire with a Side-coupled Quantum Dot

We report a transport experiment on the Fano effect in a quantum connecting wire (QW) with a side-coupled quantum dot (QD). The Fano resonance occurs between the QD and the "T-shaped" junction in the wire, and the transport detects anti-resonance or forward scattered part of the wavefunction. While in this geometry it is more difficult to tune the shape of the resonance than in the previously reported Aharonov-Bohm-ring type interferometer, the resonance purely consists of the coherent part of transport. By utilizing this advantage, we have qualitatively explained the temperature dependence of the Fano effect by including the thermal broadening and the decoherence. We have also proven that this geometry can be a useful interferometer to measure the phase evolution of electrons at a QD.Comment: REVTEX, 6 pages including 5 figures, final versio

Direct CP violation in three-body decays of the BB meson by resonance effects

We discuss direct CP violation in three-body decays of $B$ meson such as $B^\pm \to K^\pm\pi^+\pi^-$, which involves various intermediate resonance states, such as $B^\pm \to K^*_i \pi^\pm$ and $B^\pm \to \rho K^\pm$, where $K^*_i$ represents the $\pi K$ resonance. Due to the large final state interaction phases of the resonances, the CP asymmetry can be as large as the 25% level near the kinematical region where the $K^*_i$ and $\rho$ resonances overlap. By examining a Dalitz plot of this mode and combining a measurement of the branching ratio for $B^\pm \to \rho^\pm K$, it is possible to extract the weak phase, $\phi_3$= arg$(-V_{ud}V_{ub}^*/(V_{cd}V_{cb}^*))$, of the Kobayashi-Maskawa matrix.Comment: 12 pages, 1 figures. Argument to determine the CKM angle is changed. Also available via anonymous ftp at ftp://ftp.kek.jp/kek/preprints/TH/TH-54

Josephson effect of superconductors with J=3/2J=3/2 electrons

The angular momentum of an electron is characterized well by pseudospin with $J=3/2$ in the presence of strong spin-orbit interactions. We study theoretically the Josephson effect of superconductors in which such two $J=3/2$ electrons form a Cooper pair. Within even-parity symmetry class, pseudospin-quintet pairing states with $J=2$ can exist as well as pseudospin-singlet state with $J=0$. We focus especially on the Josephson selection rule among these even-parity superconductors. We find that the selection rule between quintet states is severer than that between spin-triplet states formed by two $S=1/2$ electrons. The effects of a pseudospin-active interface on the selection rule are discussed as well as those of odd-frequency Cooper pairs generated by pseudospin dependent band structures.Comment: 10 pages, 2 figure