Effects of Nuclear Field Gradients on Spin Transport*

Signatures of large nuclear fields, induced by the process of dynamic nuclear polarization, have been observed in spin transport and optical orientation experiments with n-GaAs [1,2,3]. In this work, the electron spin polarization is modeled using the spin drift-diffusion equation with various terms capturing the complex electron-nuclear spin dynamics in the system. For some boundary conditions, analytic solutions for the steady state polarization are ascertained for arbitrary applied field. Importantly, we extend the conventional spin drift-diffusion equation to include a term accounting for the nuclear field gradient which induces a spin-dependent force on the carriers. Experiments are proposed that would demonstrate the influence of nuclear field gradients on spin transport.

[1] M. Chan et al. Phys. Rev. B 80, 161206, (2009)

[2] N. J. Harmon, T. A. Peterson, C. C. Geppert, S. J. Patel, C. J. Palmstrøm, P. A. Crowell, and M. E. Flatté, Phys. Rev. B 92, 140201(R) (2015).

[3] Y.-S. Ou, Y.-H. Chiu, N. J. Harmon, P. Odenthal, M. Sheffield, M. Chilcote, R. K. Kawakami, and M. E. Flatté, Phys. Rev. Lett. 116, 107201 (2016).