Influence of the Electronic State on H Tunnelling in Niobium

Abstract

We studied by neutron spectroscopy H tunnelling states in Nb below the superconducting transition temperature in both the superconducting and normal-conducting electronic state. Our results prove the direct (nonadiabatic) interaction between tunnelling states and conduction electrons. The electronic coupling parameter is derived independently of the damping (relaxation) of the tunnelling states and of the renormalization of the tunnelling matrix elements.