SFB 668


SFB 668

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7.2.2012, 17:00
Jungiusstr. 11, Hörsaal AP

SFB 668 - Kolloquium

Prof. Walter Hofstetter (Frankfurt):

Quantum Tunneling induced Kondo Physics in Single Molecule Magnets

Recent advances in nano-fabrication have lead to the experimental realization of single molecule magnet (SMM) transistors. In this talk I will discuss effects of molecular magnetism on low-temperature electronic transport through SMMs, and its interplay with quantized vibrational distortions of the molecule. \ For half-integer molecular spin, electron- and spin-tunneling cooperate to produce a new Kondo anomaly in the linear conductance. The magnetic symmetry of the spin tunneling imposes a selection rule on the total spin for the occurrence of the Kondo effect, which deviates from the usual even-odd alteration. The Kondo energy scale, which can be much larger than the magnetic splittings of the molecular spin states, is strongly modulated by the anisotropy parameter or by a magnetic field, and can thus be used for accurate transport spectroscopy of molecular magnetic states. Based on numerical renormalization group calculations, I will discuss signatures of this molecular Kondo effect in time-dependent response measurements out of equilibrium. \ We also show that, despite the longitudinal anisotropy barrier and small transverse anisotropy, vibrational fluctuations can induce quantum spin-tunneling (QST) and a QST- Kondo effect. The interplay of spin scattering, QST and molecular vibrations can strongly enhance the Kondo effect and induce an anomalous magnetic field dependence of vibrational Kondo side-bands.

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