Stochastic Landau-Zener model, and experimental estimates of dephasing time in molecular magnets
Quantum tunneling of the magnetization in magnetic molecules (MM) with high spin value is a fascinating subject which contrasts clean and accurate experimental data with sophisticated theoretical models. At the heart of these models stands the Landau  and Zener  (LZ) derivation of quantum tunneling between levels, which at resonance have a tunnel splitting Δ, but are brought in to and out off resonance by a time-dependent field. This theory predicts transition probabilities, however, it has not been able to account for the size of the magnetization jumps in molecular magnets. In fact, the discrepancy between Δ deduced from LZ experiments  and the one calculated from spectroscopic data is more than three orders of magnitudes . In these circumstances it might be essential to analyze experiments using a broader LZ theory which includes stochastic fluctuations produced by the environment. Such a theory was developed by Shimshoni and Stern (SS) . The SS theory takes into account the dephasing effect due to stochastic field fluctuations. Combining this theory with measurements of dephasing times for MM could lead to a revision in tunnel splitting calculations. But, as far as we know, there are no estimates for dephasing time of MM. The purpose of the present work is to highlight the importance of dephasing in tunneling experiments and to measure the dephasing time.
KeywordsSweep Rate Quantum Tunneling Spin Motion Muon Spin Adiabatic Limit
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