Dephasing of quantum tunnelling in molecular nanomagnets
Zhang Shu-Qun(张树群)a) and Chen Zhi-De(陈芝得)b)†
a Department of Optoelectronic Engineering, Jinan University, Guangzhou 510632, China; b Department of Physics, Jinan University, Guangzhou 510632, China
Abstract Dephasing mechanism of quantum tunnelling in molecular magnets has been studied by means of the spin-coherent-state path integral in a mean field approximation. It is found that the fluctuating uncompensated transverse field from the dipolar-dipolar interaction between molecular magnets contributes a random phase to the quantum interference phase. The resulting transition rate is determined by the average tunnel splitting over the random phase. Such a dephasing process leads to the suppression of quenching due to the quantum phase interference, and to the steps due to odd resonances in hysteresis loop survived, which is in good agreement with experimental observations in molecular nanomagnets Fe8 and Mn$_{12}.$
Received: 14 September 2007
Revised: 14 October 2007
Accepted manuscript online:
PACS:
03.65.Xp
(Tunneling, traversal time, quantum Zeno dynamics)
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