Nuclear spin polarization in silicon nanostructures with charge carrier injection

Abstract

We theoretically examine injection polarization of nuclear spins in silicon nanostructures with hyperfine interaction of nuclei with excited triplet states. We predict the possibility of the appearance of self-sustaining nuclear spin polarization, initiated by an external field. We show that if the external magnetic field is varied, we observe up to a 600-fold jump in the number of spin-polarized nuclei. A similar up to 40-fold jump also appears as the charge carrier injection rate increases.Introduction. Study of the behavior of electronic and nuclear spins in nanostructures upon excitation of their electronic subsystem is important for spintronics and quantum calculations. Due to the insufficient sensitivity of traditional rf spectroscopy methods, optical and electrical polarization and detection methods are used for these purposes [1-3]. Using electrical methods for metrology and control of spin ensembles leads to full-fledged integration of spin systems into semiconductor electronics [4]. From this standpoint, nuclear polarization (controllable by excitation of the electronic subsystem) is promising. For example, in silicon it is due to hyperfine interaction of the 29 Si nuclei with donor or triplet centers [5][6][7]. Substantial polarization of the nuclei in the first case is achieved by excitation of the electronic subsystem with circularly polarized light in compensated silicon, containing donor and acceptor centers; in the second case, by excitation with unpolarized light in a magnetic field. In this case, the degree of nuclear polarization reaches 5%-8% of the concentration of silicon nuclei as a result of hyperfine interaction with excited triplet centers of the Si-S1 type [7]. This effect is promising for development of electronic control of nuclear polarization in silicon nanostructures.The aim of this work was to model injection polarization of silicon nuclear spins in silicon nanostructures when they interact with triplet states, taking into account the magnetic field created by the nuclei.The model. Let us describe the contact interaction of the nuclei with a triplet center with spin S = 1 using the familiar Hamiltonian in [7,8] which, taking into account the field H N = h N sIt created by the nuclei at the electron, has the form: