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Spin relaxation and decoherence of two-level systems

X. R. Wang·Y. S. Zheng·Sun Yin
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Abstract

We revisit the concepts of spin relaxation and spin decoherence of two level (spin-1/2) systems. From two toy-models, we clarify two issues related to the spin relaxation and decoherence: 1) For an ensemble of two-level particles each subjected to a different environmental field, there exists an ensemble relaxation time $T_1^*$ which is fundamentally different from $T_1$. When the off-diagonal coupling of each particle is in a single mode with the same frequency but a random coupling strength, we show that $T_1^*$ is finite while the spin relaxation time of a single spin $T_1$ and the usual ensemble decoherence time $T_2^*$ are infinite. 2) For a two-level particle under only a random diagonal coupling, its relaxation time $T_1$ shall be infinite but its decoherence time $T_2$ is finite.

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X. R. Wang, Y. S. Zheng, Sun Yin. 2005-09-16. Spin relaxation and decoherence of two-level systems. https://doi.org/10.1103/physrevb.72.121303

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