Nuclear spin dynamics and Zeno effect in quantum dots and defect centers
Abstract
We analyze nuclearspin dynamics in quantum dots and defect centers with a bound electron under electronmediated coupling between nuclear spins due to the hyperfine interaction (“ J coupling” in NMR). Our analysis shows that the Overhauser field generated by the nuclei at the position of the electron has shorttime dynamics quadratic in time for an initial nuclearspin state without transverse coherence. The quadratic shorttime behavior allows for an extension of the Overhauserfield lifetime through a sequence of projective measurements (quantum Zeno effect). We analyze the requirements on the repetition rate of measurements and the measurement accuracy to achieve such an effect. Further, we calculate the longtime behavior of the Overhauser field for effective electron Zeeman splittings larger than the hyperfine coupling strength and find, both in a Dysonseries expansion and a generalized masterequation approach, that for a nuclearspin system with a sufficiently smooth polarization the electronmediated interaction alone leads only to a partial decay of the Overhauser field by an amount of the order of the inverse number of nuclear spins interacting with the electron.
 Publication:

Physical Review B
 Pub Date:
 November 2008
 DOI:
 10.1103/PhysRevB.78.205301
 arXiv:
 arXiv:0802.2463
 Bibcode:
 2008PhRvB..78t5301K
 Keywords:

 73.21.La;
 76.20.+q;
 76.30.v;
 85.35.Be;
 Quantum dots;
 General theory of resonances and relaxations;
 Electron paramagnetic resonance and relaxation;
 Quantum well devices;
 Condensed Matter  Mesoscopic Systems and Quantum Hall Effect
 EPrint:
 11 pages, 3 figures