Incoherent Zener tunneling and its application to molecular magnets

TL;DR

This paper extends the Landau-Zener theory to include thermal relaxation, deriving an incoherent tunneling probability applicable to molecular magnets, with implications for understanding spin transitions in Fe8 crystals.

Contribution

It introduces a generalized master equation for incoherent Zener tunneling, accounting for environmental interactions, and applies it to molecular magnet experiments.

Findings

Incoherent Zener tunneling probability has an exponent twice that of the coherent case at zero temperature.

The generalized theory matches experimental data on spin tunneling in Fe8 molecular magnets.

Thermal relaxation significantly influences tunneling dynamics in molecular clusters.

Abstract

We generalize the Landau-Zener theory of coherent tunneling transitions by taking thermal relaxation into account. The evaluation of a new generalized master equation containing a dynamic tunneling rate that includes the interaction between the relevant system and its environment leads to an incoherent Zener transition probability with an exponent that is twice as large as the one of the coherent Zener probability in the limit T -> 0. We apply our results to molecular clusters, in particular to recent measurements of the tunneling transition of spins in Fe8 crystals performed by Wernsdorfer and Sessoli [Science 284, 133 (1999)].