Theory of transport through molecular magnets

Quantum transport through single molecular magnets (SMM) is starting to become a new exciting field in molecular spin electronics. Recent experiments [1,2] have shown that magnetic excitations can be identified in transport measurements and that NDC effects and complete current suppression can be explained by charge dependent anisotropies. Recent theoretical investigations [3,4,5] are presented which demonstrate fingerprints of quantum tunneling of magnetization (QTM). For weak tunneling, the violation of spin-selection rules leads to the occurence of fake resonances with temperature-dependent position [3]. For strongtunneling, it is show that a pseudo spin-1/2 Kondo effect is induced by QTM. If the Kondo temperature T$_K$ is smaller than the distance to excited magnetic states, selection rules depending on spin and symmetry of the SMM are derived for the Kondo effect to occur [4]. If T$_K$ exceeds the anisotropy barrier, it is shown that a reentrant Kondo effect can be induced by application of a longitudinal magnetic field for SMM with half-integer or integer spin [5]. This effect can be used for transport spectroscopy of the various anisotropies characterizing a SMM. \newline \newline [1] H.B. Heersche et al., Phys. Rev. Lett. 96, 206801 (2006). \newline [2] Moon-Ho Jo et al., Nano Lett. 6, 2014 (2006). \newline [3] C. Romeike, M.R. Wegewijs, H. Schoeller, Phys. Rev. Lett. 96, 196805 (2006). \newline [4] C. Romeike, M.R. Wegewijs, W. Hofstetter, H. Schoeller, Phys. Rev. Lett. 96, 196601 (2006). \newline [5] C. Romeike, M.R. Wegewijs, W. Hofstetter, H. Schoeller, to be published in Phys. Rev. Lett., cond-mat/0605514.