Zero- and one-dimensional magnetic traps for quasiparticles in diluted magnetic semiconductors

Abstract

We investigate the possibility of trapping quasi-particles possessing spin degree of freedom in hybrid structures. The hybrid system we are considering here is composed of a semi-magnetic quantum well placed a few nanometers below a ferromagnetic micromagnet. We are interested in two different micromagnet shapes: cylindrical (micro-disk) and rectangular geometry. We show that in the case of a micro-disk, the spin object is localized in all three directions and therefore zero-dimensional states are created, and in the case of an elongated rectangular micromagnet, the quasi-particles can move freely in one direction, hence one-dimensional states are formed. After calculating profiles of the magnetic field produced by the micromagnets, we analyze in detail the possible light absorption spectrum for different micromagnet thicknesses, and different distances between the micromagnet and the semimagnetic quantum well. We find that the discrete spectrum of the localized states can be detected via spatially-resolved low temperature optical measurement.

Precession of localized spins in an inhomogeneous magnetic fringe field

“…The inhomogeneity can have both desired and detrimental effects: Taking nanoscale FMs as an example, fringe field gradients are proposed to be employed for coherent single electron spin control in a quantum dot 6 and as a spin selective energy trap for carriers in FM-diluted magnetic semiconductor ͑DMS͒ hybrid structures. 7 It has been shown by micro-magneto-photoluminescence spectroscopy that a FM fringe field can be used to define and manipulate a spatially varying spin polarization in an underlying DMS quantum well ͑QW͒. 8,9 Utilizing the fringe field inhomogeneity, the precession frequency of conduction band carriers in an InGaAs/ GaAs quantum well ͑QW͒ was modulated on ns time scale by applying voltage pulses to the FMs and dragging the carriers laterally.…”

Magnetic Recording of Superconducting States

“…As a DMS layer, III-Mn-V materials, the more established II-Mn-VI, as well as the emerging Mn-containing group-IV alloys, could in principle be used to engineer spin-polarized charge-carrier states with specific features. Test devices producing the required non-uniform magnetic fields with nanoscale spatial variation could be readily obtained by introducing nanomagnets of various shapes [23][24][25] at the expense of having a rigid structure which offers no flexibility for manipulation after fabrication. However, to the best of our knowledge, an experimental corroboration of these theoretical predictions is still lacking.…”

The effect of impurities on spin-polarized Zeeman bound states in dilute magnetic semiconductor-superconductor hybrids

“…17 Using a Luttinger Hamiltonian, 18 one can also show that in a 2D QW, the g eff of heavy holes is highly anisotropic, with an in-plane component much smaller than that perpendicular to the film plane. 7 With these results in mind, we can further simplify our problem by considering only the effect of the z component of the magnetic field, which is most strongly coupled to the charge carrier. This approximation allows us to decouple the Hamiltonian in the spin-up and spin-down sector, and consider them separately.…”

“…4,6,7,10,11 Depending on the shape and orientation of the nanomagnet, different nonuniform fields are generated, giving rise to various types of confined states. 7 Another possibility is the use of Abrikosov vortices that appear in type-II superconductors (SCs). Above the lower critical field B c1 vortices populate the superconductor, forming a vortex lattice.…”