Spin inelastic electron tunneling spectroscopy on local magnetic moment embedded in Josephson junction

Department of Physics and Astronomy, Uppsala University - Box 516, SE-75120, Uppsala, Sweden

Received: 2 October 2014
Accepted: 4 December 2014

Abstract

Recent experimental conductance measurements performed on paramagnetic molecular adsorbates on a superconducting surface, using superconducting scanning tunneling microscopy techniques, are theoretically investigated. For low temperatures, we demonstrate that tunneling current assisted excitations of the local magnetic moment cannot occur for voltage biases smaller than the superconducting gap of the scanning tunneling microscope. The magnetic moment is only excited for voltages corresponding to the sum of the superconducting gap and the spin excitation energies. In excellent agreement with experiment, we show that pumping into higher excitations gives additional current signatures by accumulation of density in the lower ones. Using external magnetic fields, we Zeeman-split the possible degeneracy and thereby resolve all excitations comprised in the magnetic moment.