Mechanisms of spin-charge conversion for the electrical readout of 4f quantum states in a TbPc2 single-molecule magnet spin transistor

We present a theoretical study exposing the dominant microscopic electronic transport mechanisms underlying a recent molecular spin-transistor experiment [C. Godfrin et al., ACS Nano 11, 3984 (2017)], where purely electrical readout of the spin of a Tb(III)-based single-molecule magnet was achieved. To identify the relevant spin-to-charge conversion mechanisms enabling opposite spin polarizations of the Tb(III) ion 4f electrons to generate different magnetoconductance responses, we investigate both incoherent sequential tunneling charge transport, and coherent cotunneling corrections. Contrary to previous interpretations invoking the highly coherent Kondo transport regime, we find that all reported experimental observations, including the temperature and magnetic field dependence of the differential conductance, can be reproduced reasonably well within a sequential tunneling transport regime explicitly accounting for broadening of the device energy levels due to molecule-lead coupling.