Y. Tanuma

Theory of Tunneling Conductance for Normal Metal/Insulator/ Triplet Superconductor Junction

Tunneling conductance spectra of normal metal/insulator/triplet superconductor junctions are investigated theoretically. As triplet paring states we select several types of symmetries that are promising candidates for the superconducting states in UPt3 and in Sr2RuO4. The calculated conductance spectra are sensitive to the orientation of the junction which reflects the anisotropy of the pairing states. They show either zero-bias conductance peaks or gap-like structures depending on the orientation of the junctions. The existence of a residual density of states, peculiar to nonunitary states, is shown to have a significant influence on the properties of the conductance spectra. Present results serve as a guide for the experimental determination of the symmetry of the pair potentials in UPt3 and Sr2RuO4.

Theory of Local Density of States of d x2- y2-Wave Superconducting State Near the Surfaces of the t- J Model

Spatial dependencies of the pair potential and the local density of states near the surfaces of d x 2 - y 2 -wave superconductors are studied theoretically. The calculation is based on the t - J model within a mean-field theory with Gutzwiller approximation. Various types of surface geometries are considered. Similar to our result in the extended Hubbard model, it is found that the formation of zero-energy states strongly depends on the surface geometry. In addition to this feature, the zero-energy states give peak splitting for the (110) surfaces when the super-exchange interaction J is large. This is due to the induced s -wave component near the surface. The present result explains the microscopic origin of the spontaneous time-reversal symmetry breaking at the surfaces of high- T c superconductors.Spatial dependencies of the pair potential and the local density of states near the surfaces of d x 2 - y 2 -wave superconductors are studied theoretically. The calculation is based on the t - J model within a mean-field theory with Gutzwiller approximation. Various types of surface geometries are considered. Similar to our result in the extended Hubbard model, it is found that the formation of zero-energy states strongly depends on the surface geometry. In addition to this feature, the zero-energy states give peak splitting for the (110) surfaces when the super-exchange interaction J is large. This is due to the induced s -wave component near the surface. The present result explains the microscopic origin of the spontaneous time-reversal symmetry breaking at the surfaces of high- T c superconductors.

Odd-frequency pairing in normal-metal/superconductor junctions

We theoretically study the induced odd-frequency pairing states in ballistic normal-metal/superconductor (N/S) junctions where a superconductor has even-frequency symmetry in the bulk and a normal-metal layer has an arbitrary length. Using the quasiclassical Greens function formalism, we demonstrate that, quite generally, the pair amplitude in the junction has an admixture of an odd-frequency component due to the breakdown of translational invariance near the N/S interface where the pair potential acquires spatial dependence. If a superconductor has an even-parity pair potential (spin-singlet s-wave or spin-singlet dxy-wave state), the odd-frequency pairing component with odd parity is induced near the N/S interface, while in the case of an odd-parity pair potential (spin-triplet px wave) the odd-frequency component with even parity is generated. We show that in conventional s-wave junctions, the amplitude of the odd-frequency pairing state is strongest in the case of a full-transparency N/S interface and is enhanced at energies corresponding to the peaks in the local density of states (LDOS). In px- and dxy-wave junctions, the amplitude of the odd-frequency component on the S side of the N/S interface is enhanced at zero energy where the midgap Andreev resonant state (MARS) appears due to the sign change of the pair potential. The odd-frequency component extends into the N region and exceeds the even-frequency component at energies corresponding to the LDOS peak positions, including the MARS. At the edge of the N region the odd-frequency component is nonzero while the even-frequency one vanishes. We show that the concept of the odd-frequency pairing state plays a pivotal role to interpret a number of phenomena in nonuniform superconducting systems, like McMillan-Rowell and midgap Andreev resonance states.

Tunneling conductance of normal metal/ d x 2 − y 2 -wave superconductor junctions in the presence of broken time-reversal symmetry states near interfaces

In order to clarify the influence of (the presence of) the broken time-reversal symmetry state (BTRSS) induced near the interface, tunneling conductance spectra in normal metal/

Determination of pairing symmetry from magnetotunneling spectroscopy: A case study for quasi-one-dimensional organic superconductors

{d}_{{x}^{2}\ensuremath{-}{y}^{2}}

TUNNELING SPECTROSCOPY AND PAIRING SYMMETRY OF THE HIGH-TC SUPERCONDUCTORS

-wave superconductor junctions are calculated on the basis of the quasiclassical Greens function method. The spatial dependence of the pair potential in the superconductor side is determined self-consistently. We discuss two types of the symmetry on the BTRSS: (i)

Theory of Magnetotunneling Spectroscopy in Spin Triplet p-Wave Superconductors

{d}_{{x}^{2}\ensuremath{-}{y}^{2}}+is

Model for vortex-core tunneling spectroscopy of chiral p-wave superconductors via odd-frequency pairing states.

-wave state and (ii)

Influence of Magnetic Field on Tunneling Conductance in Normal Metal/ dx2-y2-Wave Superconductor Junctions

{d}_{{x}^{2}\ensuremath{-}{y}^{2}}{+id}_{\mathrm{xy}}

Tunneling conductance in normal metal-High-TC cuprate junctions in the presence of magnetic field

-wave state. It is shown that the amplitude of the subdominant component