Disentangling 4f -radical coupling and dissipative Landau-Zener quantum tunneling in a continuously measured single-ion magnet spin transistor

Both radical-lanthanide exchange coupling and crystal-field tunnel splitting are responsible for the ground to first-excited Kramers doublet energy gap ΔEKD in an Ising 4f single-ion magnet coupled to a noninnocent ligand. However, these two mechanisms cannot be easily disentangled via spectroscopy alone because their interplay results in a single absorption line. Here we present a microscopic theory for the continuous measurement of the dissipative Landau-Zener transitions recently discussed for a TbPc2 spin transistor [Phys. Rev. Lett. 118, 257701 (2017)]PRLTAO0031-900710.1103/PhysRevLett.118.257701 and show how this quantum transport experiment can be used to disentangle the magnetic coupling and the tunnel splitting contributions to ΔEKD. In addition, our model elucidates the microscopic origin of the decoherent spin tunneling observed in the TbPc2 spin transistor, by explicitly exposing the role played by phonon-mediated spin relaxation and sequential electron transport through the noninnocent ligand, in a time-dependent magnetic field.