Seminar by Dimitrije Stepanenko

SCL hosted IPB-wide seminar by Dimitrije Stepanenko from the Department of Physics, University of Basel, Switzerland on 16 February 2010, entitled "Spin-electric coupling and coherent quantum control of molecular nanomagnets ".

Abstract of the talk:
Molecular nanomagnets show clear signatures of coherent quantum behavior and have a wide variety of effective low-energy spin Hamiltonians suitable for encoding qubits and implementing spin-based quantum information processing.

The most straightforward and traditional way of controlling magnetic molecules is by applying an external magnetic field. Unfortunately, the quantum manipulation has to be performed on the very short spatial and temporal scales, while the local application of rapidly varying magnetic field presents a challenging experimental problem. At the nanoscale, the preferred mechanism for control of quantum systems is through application of electric fields, which are strong, can be locally applied, and rapidly switched.

We study molecular antiferromagnets in external electric fields, using symmetry group arguments and a Hubbard model approach. We identify a spin-electric coupling caused by an interplay between spin exchange, spin-orbit interaction, and the chirality of the underlying spin texture of the molecular nanomagnet. While the general theory can predict a class of molecules in which the spin-electric coupling is likely to appear, the search for suitable qubit candidates will necessarily involve experimental work. We therefore investigate the possible signatures of spin-electric coupling in electron spin resonance and nuclear magnetic resonance spectroscopy, as well as in the thermodynamic properties of candidate molecules. Once found, this coupling allows for the electric control of spin states, e.g. by using an STM tip or a microwave cavity.

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