Probing Coherent Spin Dynamics of Isolated Exchange Coupled Defects in III-V Semiconductors*

Individual magnetic impurities or small collections of magnetic impurities in III-V semiconductors can be identified via scanning tunneling microscopy (STM) [1,2]. Their exchange interaction can be measured [3], and they can have remarkably long spin coherence times [4]. Through low-field magnetoresistance calculations we find that exchange coupled defects generate a resonance feature in the current at critical values of the applied magnetic field, termed "exchange resistance". Using a single site approximation [5,6], the signatures of hyperfine interaction and the influence of g-factor fluctuation on exchange resistance are examined. By including a non-trivial spin manifold as the ground state this work becomes applicable to defects like divacancies in silicon carbide and Mn+hole complexes in gallium arsenide.

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[3] D. Kitchen et al., Nature 442, 436 (2006).
[4] R. C. Myers et al., Nature Materials 7, 203 (2008).
[5] H. Inoue et al., Phys. Rev. X 5, 041023 (2015)
[6] N. J. Harmon and M. E. Flatté, Phys. Rev. B 98, 035412 (2018)