Surface Bound States in n-band Systems with Quasiclassical Approach

We discuss the tunneling spectroscopy at a surface in multi-band systems such as Fe-based superconductors with the use of the quasiclassical approach. We extend the single-band method by Matsumoto and Shiba [J. Phys. Soc. Jpn. 64, 1703 (1995)] into $n$-band systems ($n \geq 2$). We show that the appearance condition of the zero-bias conductance peak does not depend on details of the pair-potential anisotropy, but it depends on details of the normal state properties in the case of fully-gapped superconductors. The surface density of states in a two-band superconductor is presented as a simplest application. The quasiclassical approach enables us to calculate readily the surface-angular dependence of the tunneling spectroscopy.Comment: 9 pages, 7 figures; References and Discussions update

Fluctuation theorem for the renormalized entropy change in the strongly nonlinear nonequilibrium regime

Generalizing a recent work [T. Taniguchi and E. G. D. Cohen, J. Stat. Phys. 126, 1 (2006)] that was based on the Onsager-Machlup theory, a nonlinear relaxation process is considered for a macroscopic thermodynamic quantity. It is found that the fluctuation theorem holds in the nonlinear nonequilibrium regime if the change of the entropy characterized by local equilibria is appropriately renormalized. The fluctuation theorem for the ordinary entropy change is recovered in the linear near-equilibrium case. This result suggests a possibility that the the information-theoretic entropy of the Shannon form may be modified in the strongly nonlinear nonequilibrium regime.Comment: 14 pages, no figures. Typos correcte

Strongly Enhanced DD Fusion Reactions at Very Low Energies in Solids(I. Nuclear Physics)

The interplay between a nucleus and its environment is known to play an important role in nuclear reactions when the incident energy has been reduced far below the Coulomb barrier, where the cross section described by the Gamow function decreases drastically due to the steep drop in the quantum mechanical penetration of the barrier. For the fusion reactions in metals, experimental techniques were developed in which target nuclei were implanted in a metal. The DD fusion reactions were studied, so far, and an enhancement in the rate of the D(d, p)T fusion reaction over the Gamow function was found for deuterons in Ti and Yb. Here we report on further measurements of the D+D reactions in other materials. Of particular interest is the fact that the reaction rate of the D+D reactions at 2.5 keV in PdO is 50 times larger than in Ti, and the deduced screening potential amounts to 600 eV. This cannot be explained by bound-electron screening which may give a potential of 20 eV at most, but suggests the existence of an additional, and important, mechanism. Perhaps there is a fluidity of deuterons in metals that also reduces the Coulomb barrier between the interacting deuteron pair. An exhaustive study of nuclear reactions in metal would be very significant ; one would then not only simulate nuclear fusion reactions in a stellar plasma where the nuclei are immersed in a sea of electrons, but also explore the limitations of nuclear fusion at room temperature