Condensed Matter Physics Seminar
Wed, Nov 20
4:00 PM — 5:00 PM
Marshak Science Building160 Convent Ave.New York, NY 10031
Marshak Science Building, 418N
Enrique del Barco, Department of Physics, University of Central Florida, Orlando, FloridaQuantum Tunneling of the Magnetization in Molecular Magnets: A Microscopic View
Enrique del Barco
Department of Physics, University of Central Florida, Orlando, Florida 32816, USA
Intensive research efforts during the last few years have led to a significant enhancement of the current knowledge of magnetic bistability and quantum tunneling of the magnetization (MQT) in single-molecule magnets (SMMs). A good part of this new understanding has been allowed by studies of families of relatively simple, low-nuclearity transition metal clusters, where the low number of ions responsible for the magnetic behavior of the molecule enables a full numerical treatment of the multi-spin Hamiltonian, where degrees of freedom associated to the individual ions can be adequately tested. These include exchange and dipolar interactions, single-ion zero-field splitting tensors (i.e. single-ion anisotropy order and orientation), and intra-molecular symmetries, among others. In addition, comparisons between the giant spin and the multi-spin phenomenologies can be easily undertaken. Note that the giant spin approach assumes the molecule to behave as a rigid spin unit, leaving out the intra-molecular degrees of freedom, and ultimately failing to capture many of the key physics. In this talk I will summarize the most relevant results achieved by following this particular research approach, including the first observation of QTM selection rules that reflect the intrinsic symmetry of a SMM [1,2], and the observation of asymmetric quantum Berry phase interference patterns in a Mn-based SMM , among others, placing special emphasis in explaining the way internal molecular degrees of freedom intervene to shape these fundamental QTM properties.
 J. J. Henderson, C. Koo, P. L. Feng, E del Barco, S. Hill, I. S. Tupitsyn, P. C. E. Stamp and D. N. Hendrickson, Manifestation of spin selection rules on the quantum tunneling of magnetization in a single-molecule magnet, Phys. Rev. Lett. 103, 017202 (2009).
 J. Liu, E. del Barco and S. Hill. Quantum tunneling of magnetization in trigonal single-molecule magnets, Phys. Rev. B. 85, 012406 (2012).
 H. M. Quddusi, J. Liu, S. Singh, K. J. Heroux, E. del Barco, S. Hill, and D. N. Hendrickson, Asymmetric Berry-Phase Interference Patterns in a Single-Molecule Magnet, Phys. Rev. Lett. 106, 227201 (2011).