SPIN TRANSPORT IN MULTIPLY CONNECTED FRACTAL CONDUCTORS

We consider spin and charge transport in a Sierpinski planar carpet; the interest here is its unique geometry. We analyze the fractal conductor as a combination of multiply connected quantum wires, and we observe the evolution of the transmission envelope in different fractal generations. For a fractal conductor dominated by resonant modes the transmission is characterized by strong fluctuations and conduction gaps. We show that charge and spin transport have different responses both to the presence of defects and to applied bias. At a high bias, or in a high-order fractal generation, spin accumulation is separated from charge accumulation because the larger drift velocity needs a longer polarization length, and the sample may turn into an insulator by the action of the defects. Our results are calculated numerically using the Keldysh Green function within the tight-binding framework.

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Effective Hamiltonian for silicene under arbitrary strain from multi-orbital basis

Scientific Reports ◽

10.1038/s41598-021-86947-z ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Zhuo Bin Siu ◽

Mansoor B. A. Jalil

Keyword(s):

Tight Binding ◽

Spin Torque ◽

Spin Accumulation ◽

Effective Hamiltonian ◽

Fermi Surfaces ◽

Orbital Basis ◽

Lattice Symmetry ◽

Out Of Plane ◽

Coupling Parameters ◽

Spin Orbit Interactions

AbstractA tight-binding (TB) Hamiltonian is derived for strained silicene from a multi-orbital basis. The derivation is based on the Slater–Koster coupling parameters between different orbitals across the silicene lattice and takes into account arbitrary distortion of the lattice under strain, as well as the first and second-order spin–orbit interactions (SOI). The breaking of the lattice symmetry reveals additional SOI terms which were previously neglected. As an exemplary application, we apply the linearized low-energy TB Hamiltonian to model the current-induced spin accumulation in strained silicene coupled to an in-plane magnetization. The interplay between symmetry-breaking and the additional SOI terms induces an out-of-plane spin accumulation. This spin accumulation remains unbalanced after summing over the Fermi surfaces of the occupied bands and the two valleys, and can thus be utilized for spin torque switching.

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Selective spin transport through a quantum heterostructure: Transfer matrix method

International Journal of Modern Physics B ◽

10.1142/s0217979216501848 ◽

2016 ◽

Vol 30 (25) ◽

pp. 1650184 ◽

Cited By ~ 6

Author(s):

Moumita Dey ◽

Santanu K. Maiti

Keyword(s):

Transfer Matrix ◽

Transfer Matrix Method ◽

Matrix Method ◽

Spin Transport ◽

Tight Binding ◽

Transmission Probability ◽

Applied Bias Voltage ◽

One Dimensional ◽

Wide Range ◽

Nanoscale Level

In the present work, we propose that a one-dimensional quantum heterostructure composed of magnetic and non-magnetic (NM) atomic sites can be utilized as a spin filter for a wide range of applied bias voltage. A simple tight-binding framework is given to describe the conducting junction where the heterostructure is coupled to two semi-infinite one-dimensional NM electrodes. Based on transfer matrix method, all the calculations are performed numerically which describe two-terminal spin-dependent transmission probability along with junction current through the wire. Our detailed analysis may provide fundamental aspects of selective spin transport phenomena in one-dimensional heterostructures at nanoscale level.

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Theoretical study of the vanadyl-oxygen vacancy in V2O5: tight-binding Green function calculation, optical properties and neutral vacancy ground-state splitting

Journal of Physics C Solid State Physics ◽

10.1088/0022-3719/19/3/007 ◽

1986 ◽

Vol 19 (3) ◽

pp. 369-388 ◽

Cited By ~ 8

Author(s):

W Lambrecht ◽

B Djafari-Rouhani ◽

J Vennik

Keyword(s):

Optical Properties ◽

Green Function ◽

Oxygen Vacancy ◽

Ground State ◽

Theoretical Study ◽

Tight Binding ◽

State Splitting ◽

Function Calculation

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DILUTED FERROMAGNETIC SEMICONDUCTORS — ORIGIN OF MAGNETIC ORDERING AND SPIN-TRANSPORT PROPERTIES

International Journal of Modern Physics B ◽

10.1142/s0217979208046116 ◽

2008 ◽

Vol 22 (01n02) ◽

pp. 104-105 ◽

Cited By ~ 1

Author(s):

TOMASZ DIETL

Keyword(s):

Diluted Magnetic Semiconductors ◽

Spin Transport ◽

Correlation Energy ◽

Tight Binding ◽

Spin Current ◽

Magnetic Ordering ◽

Exchange Interactions ◽

Ferromagnetic Phase ◽

Magnetic Characteristics ◽

Ferromagnetic Semiconductors

In the first hour of the lecture the present understanding of the origin of exchange interaction and mechanisms leading to ferromagnetic order in diluted magnetic semiconductors will be presented.1 The lecture will start by discussing energy positions of relevant open magnetic shells, including the correlation energy and excitations within the magnetic ions. The origin and magnitude of sp–d exchange interactions will then be described. This will be followed by presenting the physics of indirect exchange interactions between localized spins contrasting magnetic characteristics in the absence and in the presence of free carriers. The Zener and RKKY models of ferromagnetism will be introduced and the role of confinement, dimensionality, and spin-orbit interaction in determining properties of the ferromagnetic phase will be outlined. The second lecture will be devoted to theory of spin transport in layered structures of diluted ferromagnetic semiconductors, emphasizing the issues important for perspective spintronics devices. A recently developed theory,2 which combines a multi-orbital empirical tight-binding approach with a Landauer–Büttiker formalism will be presented. In contrast to the standard kp method, this theory describes properly the interfaces and inversion symmetry breaking as well as the band dispersion in the entire Brillouin zone, so that the essential for the spin-dependent transport Rashba and Dresselhaus terms as well as the tunneling via k points away from the zone center are taken into account. The applicability of this model for the description of tunneling magnetoresistance (TMR), resonant tunneling spectra, spin-current polarization in Esaki-Zener diodes, and domain-wall resistance will be presented. Note from Publisher: This article contains the abstract only.

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