title: Effect of time reversal symmetry breaking on the density of states in small superconducting grains
abstract: 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.
authors.affiliation: Theoretische Physik III, Ruhr-Universitat Bochum, 44780 Bochum, Germany.
authors.initials: IS
authors.lastname: Beloborodov
authors.initials: BN
authors.lastname: Narozhny
authors.initials: IL
authors.lastname: Aleiner