新论文:量子点中的核磁场是如何衰减的


在段老师的指导下,我与同学龚哲轩合作完成了一篇论文,讨论了量子点中核磁场如何通过自由扩散衰减,以及衰减速率与外加磁场强度,量子点的电子状态以及核磁场本身的初始分布之间的关系。这个结果对最近的若干实验结果给出了一个统一的理论解释,希望能对通过控制核磁场来延长量子点相干时间的实验有所帮助。

Dynamics of Overhauser Field under nuclear spin diffusion in a quantum dot

Zhe-xuan Gong, Zhang-qi Yin and L.-M. Duan

The coherence of electron spin can be significantly enhanced by locking the Overhauser field from nuclear spins using the nuclear spin preparation. We propose a theoretical model to calculate the long time dynamics of the Overhauser field under intrinsic nuclear spin diffusion in a quantum dot. We obtain a simplified diffusion equation that can be numerically solved and show quantitatively how the Knight shift and the electron-mediated nuclear spin flip-flop affect the nuclear spin diffusion. The results explain several recent experimental observations, where the decay time of Overhauser field is measured under different configurations, including variation of the external magnetic field, the electron spin configuration in a double dot, and the initial nuclear spin polarization rate.

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