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arXiv 1003.2088cond-mat.mes-hallcond-mat.other
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石墨烯量子点自旋弛豫中的有效时间反演对称性破缺

Effective time-reversal symmetry breaking in the spin relaxation in a graphene quantum dot

P. R. Struck, Guido Burkard

摘要:

研究了带隙石墨烯中圆形可调谐量子点中单电子自旋的弛豫。电子自旋通过内禀自旋-轨道耦合直接耦合到面外声子,导致弛豫时间T_1在低场下与B场无关。我们还发现,Rashba自旋-轨道诱导的相反自旋态的混合物与面内声子的发射相结合,通过变形势和键长变化提供了各种进一步的弛豫通道。在没有谷混合的情况下,自旋弛豫分别发生在每个谷内,因此时间反演对称性被有效地破坏,从而抑制了GaAs量子点中已知的B=0处的范弗莱克抵消。vanVleck相消和面外声子的不存在导致低磁场下自旋弛豫速率的行为,这与GaAs的已知结果明显不同。对于低B场,我们发现速率在B中是恒定的,然后在更高的场中跨越到~B^2或~B^4。

英文摘要:

We study the relaxation of a single electron spin in a circular gate-tunbable quantum dot in gapped graphene. Direct coupling of the electron spin to out-of-plane phonons via the intrinsic spin-orbit coupling leads to a relaxation time T_1 which is independent of the B-field at low fields. We also find that Rashba spin-orbit induced admixture of opposite spin states in combination with the emission of in-plane phonons provides various further relaxation channels via deformation potential and bond-length change. In the absence of valley mixing, spin relaxation takes place within each valley separately and thus time-reversal symmetry is effectively broken, thus inhibiting the van Vleck cancellation at B=0 known from GaAs quantum dots. Both the absence of the van Vleck cancellation as well as the out-of-plane phonons lead to a behavior of the spin relaxation rate at low magnetic fields which is markedly different from the known results for GaAs. For low B-fields, we find that the rate is constant in B and then crosses over to ~B^2 or ~B^4 at higher fields.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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