Effect of time reversal symmetry breaking on the density of states in small superconducting grains

We show that in ultrasmall superconducting grains any concentration of magnetic impurities or infinitely small orbital effect of magnetic field leads to destruction of the hard gap in the tunneling density of states, and find analytically the exponential tail at low energies. Thus, the tunneling density of states exhibits the "soft gap" behavior. As the energy approaches zero, it vanishes linearly with excitation energy.

Effect of Coupling between Rotational and Translational Brownian Motions on NMR Spin Relaxation: Consideration Using Green Function of Rigid Body Diffusion.

Using the Green function of arbitrary rigid Brownian diffusion (Goldstein, Biopolymers 33, 409-436, 1993), it was analytically shown that coupling between translation and rotation diffusion degrees of freedom does not affect the correlation functions relevant to the NMR intramolecular relaxation. It follows that spectral densities usually used for the anisotropic rotation diffusion (Woessner, J. Chem. Phys. 37, 647-654, 1962) can be regarded as exact in respect to the rotation-translation coupling for the spin system connected with a rigid body. Copyright 1998 Academic Press.