Resonant tunnelling and quenching of tunnel splitting in Wess-Zumino   nanospin systems
  We investigate the energy spectrum of the biaxial spin systems with magnetic field along the hard anisotropy axis by using the complex periodic orbit theory. All important features of the system appearing in whole energy range, such as oscillations of level splittings due to Wess-Zumino effect and their absence at higher magnetic field etc., can be completely understood within this semiclassical scheme. We find out that the fields at which the tunnelling quenches do not shift at higher energy levels and the absences of the quenching at higher magnetic field have their origin in an exact coincidence of the quenching field with the field of resonant tunnelling. Based on the result, we propose that the complete cancellation of quenching with resonant tunnelling would be a general property of Wess-Zumino tunnelling systems. 
Soo-Young Lee and Sahng-Kyoon Yoo