Khaetskii Alexander V, Loss Daniel, Glazman Leonid
Department of Physics and Astronomy, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland.
Phys Rev Lett. 2002 May 6;88(18):186802. doi: 10.1103/PhysRevLett.88.186802. Epub 2002 Apr 19.
We study the decoherence of a single electron spin in an isolated quantum dot induced by hyperfine interaction with nuclei. The decay is caused by the spatial variation of the electron wave function within the dot, leading to a nonuniform hyperfine coupling A. We evaluate the spin correlation function and find that the decay is not exponential but rather power (inverse logarithm) lawlike. For polarized nuclei we find an exact solution and show that the precession amplitude and the decay behavior can be tuned by the magnetic field. The decay time is given by (planck)N/A, where N is the number of nuclei inside the dot, and the amplitude of precession decays to a finite value. We show that there is a striking difference between the decoherence time for a single dot and the dephasing time for an ensemble of dots.
我们研究了与原子核超精细相互作用所诱导的孤立量子点中单个电子自旋的退相干。这种衰减是由量子点内电子波函数的空间变化引起的，导致超精细耦合A不均匀。我们评估了自旋相关函数，发现衰减不是指数形式的，而是幂（反对数）律形式的。对于极化的原子核，我们找到了精确解，并表明进动幅度和衰减行为可以通过磁场进行调节。衰减时间由（普朗克）N/A给出，其中N是量子点内原子核的数量，进动幅度衰减到一个有限值。我们表明，单个量子点的退相干时间与量子点集合的去相位时间之间存在显著差异。
