Site-selective NMR for odd-frequency Cooper pairs around vortex in chiral p-wave superconductors

In order to identify the pairing symmetry with chirality, we study site-selective NMR in chiral p-wave superconductors. We calculate local nuclear relaxation rate 1/T_1 in the vortex lattice state by Eilenberger theory, including the applied magnetic field dependence. We find that 1/T_1 in the NMR resonance line shape is different between two chiral states p_{pm}(=p_x{pm}ip_y), depending on whether the chirality is parallel or anti-parallel to the vorticity. Anomalous suppression of 1/T_1 occurs around the vortex core in the chiral p_- wave due to the negative coherence term coming from the odd-frequency s-wave Cooper pair induced around the vortex with Majorana state.Comment: 6 pages, 4 figure

Lower Critical Field Hc1(T) and Pairing Symmetry Based on Eilenberger Theory

We quantitatively estimate different T-dependences of Hc1 between s wave and d wave pairings by Eilenberger theory. The T-dependences of Hc1(T) show quantitative deviation from those in London theory. We also study differences of Hc1(T) between p+ and p- wave pairing in chiral p wave superconductors. There, Hc1(T) is lower in p- wave pairing, and shows the same T-dependence as in s wave pairing.Comment: 2 pages, 1 figur

NMR relaxation time around a vortex in stripe superconductors

Site-dependent NMR relaxation time $T_1({\bf r})$ is calculated in the vortex state using the Bogoliubov-de Gennes theory, taking account of possible "field-induced stripe'' states in which the magnetism arises locally around a vortex core in d-wave superconductivity. The recently observed huge enhancement $T_1^{-1}({\bf r})$ below $T_c$ at a core site in Tl$_2$Ba$_2$CuO$_6$ is explained. The field-induced stripe picture explains consistently other relevant STM and neutron experiments.Comment: 4 pages, 4 figure

Anisotropic Diamagnetic Response in Type-II Superconductors with Gap and Fermi-Surface Anisotropies

Effects of anisotropic gap structures on a diamagnetic response are investigated in order to demonstrate that the field-angle-resolved magnetization ($M_L(\chi)$) measurement can be used as a spectroscopic method to detect gap structures. Our microscopic calculation based on the quasiclassical Eilenberger formalism reveals that $M_L(\chi)$ in a superconductor with four-fold gap displays a four-fold oscillation reflecting the gap and Fermi surface anisotropies, and the sign of this oscillation changes at a field between $H_{c1}$ and $H_{c2}$. As a prototype of unconventional superconductors, magnetization data for borocarbides are also discussed.Comment: 5 pages, 4 figure

The effect of nonmagnetic impurities on the local density of states in s-wave superconductors

We study the effect of nonmagnetic impurities on the local density of states (LDOS) in s-wave superconductors. The quasiclassical equations of superconductivity are solved selfconsistently to show how LDOS evolves with impurity concentration. The spatially averaged zero-energy LDOS is a linear function of magnetic induction in low fields, N(E=0)=cB/H_{c2}, for all impurity concentration. The constant of proportionality "c" depends weakly on the electron mean free path. We present numerical data for differential conductance and spatial profile of zero-energy LDOS which can help in estimating the mean free path through the LDOS measurement.Comment: 7 pages, 7 figures (high quality color figure available on request

Topological Structure of a Vortex in Fulde-Ferrell-Larkin-Ovchinnikov State

We find theoretically that the vortex core in the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state is quite different from the ordinary core by a simple topological reason. The intersection point of a vortex and nodal plane of the FFLO state empties the excess spins. This leads to observable consequences in the spatial structure of the spontaneous magnetization. We analyze this topological structure based on the low lying excitation spectrum by solving microscopic Bogoliubov-de Gennes equation to clarify its physical origin.Comment: 4 pages, 4 figure