Features of Microwave Magnetic Dynamics in Nanostructures with Strong Spin–Orbit Interaction

Features of the current spin–orbit induced magnetic dynamics in multilayer nanostructures with nonmagnetic heavy metal layers possessing by a strong spin–orbit interaction are studied. The spin Hall effect of the conversion of an incoming charge current into a transverse (with respect to the charge current) spin current impacting on the magnetic dynamics through a spin-transfer torque provides the excitation of the magnetic dynamics including magnetic precession and switching. The magneto-dynamic effect of a spin current pumping generation together with the inverse spin Hall effect of conversion of the spin current into the incoming charge current provide the influence of the magnetic dynamics on the incoming charge current. These feedforward and feedback between the incoming charge current and the magnetic dynamics can be the basis for the spin–orbit driven self-sustained and auto-oscillations of a magnetic order in ferro- and antiferromagnetics layers of the nanostructures. It is shown that the considered magnetic nanostructures can possess by properties of controlled microwave radiation attaining tens THz in the antiferromagnetic case.Изучаются особенности магнитной динамики, индуцируемой входным зарядовым током и спин-орбитальным взаимодействием в многослойных наноструктурах с немагнитными прослойками на основе тяжёлых металлов с сильным спин-орбитальным взаимодействием. Спиновый эффект Холла превращения входного зарядового тока в поперечный (относительно зарядового тока) спиновый ток, действующий на магнитную динамику через передачу спинового крутильного момента, обеспечивает изменение магнитной динамики, включающей прецессию и переключение. Магнитодинамический эффект генерирования спинового тока накачки вместе с обратным эффектом Холла превращения спинового тока в зарядовый ток обеспечивает влияние магнитной динамики на входной зарядовый ток. Такие прямое и обратное воздействия между входным зарядовым током и магнитной динамикой могут представлять основу для спин-орбитально управляемой осцилляции магнитного порядка в ферро- или антиферромагнитных прослойках. Показано, что исследуемые магнитные наноструктуры могут обладать свойствами контролируемого микроволнового излучения, достигающего десятков ТГц в случае антиферромагнитных материалов.Вивчаються особливості магнетної динаміки, індукованої вхідним зарядовим струмом і спін-орбітальною взаємодією в багатошарових наноструктурах з немагнетними прошарками на основі важких металів зі сильною спін-орбітальною взаємодією. Спіновий Голлів ефект перетворення вхідного зарядового струму в поперечний (відносно зарядового струму) спіновий струм, діючий на магнетну динаміку через передачу спінового крутильного моменту, забезпечує збудження магнетної динаміки, включаючи прецесію та перемикання. Магнетодинамічний ефект ґенерування спінового струму накачки разом зі зворотнім Голловим ефектом перетворення спінового струму в зарядовий струм забезпечує вплив магнетної динаміки на вхідний зарядовий струм. Такі прямий і зворотній впливи між вхідним зарядовим струмом і магнетною динамікою можуть становити основу спін-орбітально керованої осциляції магнетного порядку в феро- або антиферомагнетних прошарках наноструктур. Показано, що досліджувані магнетні наноструктури можуть мати властивості контрольованого мікрохвильового випромінення, що може досягати десятків ТГц у випадку антиферомагнетних матеріялів

Electron tunneling in a multibarrier potential

The electron and spin transport in nanoscopical heterostructures taking is considered taking into account features of electron spectra. It is shown efficiency of effective mass methods for an quantum-mechanical description of electron tunneling through potential barriers of the system. It is shown the description of coherent electron transport in multibarrier electron potentials

Quantum dynamics of a two-level system under extrenal field

We present exact analytic solutions for non-linear quantum dynamics of twolevel system (TLS) subject to periodic-in-time external field. >n constructing the exactly solvable models, we use approach where the form of external perturbation is chosen to preserve n integrability constraint, which yields single non-linear differential equation for the ac-field. solution to this equation is expressed in terms of Jacobi elliptic functions with three independent parameters that allows n to choose the frequency, average value, and amplitude of the time-dependent field at will. This form of the ac-drive is especially relevant to the problem of dynamics of TLS charge defects that cause dielectric losses ?n superconducting qubits

On calculation electronic states of carbon nanotubes

A new approach is development for description of physical properties of carbon nanotubes h taking into account their real atomic structure have been proposed. On the basis of the classical polynomial theory we have investigated main quantum of studding system. On the basis a functional integral representation for a statistic sum we have proposed an effective method for building of the closed self-consisted equations for Green functions of investigating system. The proposed approach is applicable for calculation of physical properties both single- and multiwall carbon nanotubes

Collective excitations in carbon nanotubes

The effective action functional has been built by a functional integral method for nanotubes. The closed, self-consistent system of equations of the system is built on the basis of the variational differentiation the effective action on collective variables of an electron-phonon subsystem. A general expression for a polarization function and spectrum of the system are considered

The time-dependet quantum transport in nanosystems

We propose a time-dependent many-body approach to study the short-time dynamics of correlated electrons in quantum transport through nanoscale systems contacted to metallic leads. This approach is based on the time propagation of the Kadanoff-Baym equations for the nonequilibrium many-body Green’s function of open and interacting systems out of equilibrium

Photon-induced spin transport in two-dimensional electron systems

We study spin-dependent transport in a two-dimensional electron gas subject to an external step-like potential V(x) and irradiated by an electromagnetic field (EF). In the absence of EF the electronic spectrum splits into spin sub-bands originating from the "Rashba" spin-orbit coupling. We show that the resonant interaction of propagating electrons with the component EF parallel to the barrier induces a nonequilibrium dynamic gap (2ΔR ) between the spin sub-bands. Existence of this gap results in coherent spin-flip processes that lead to a spin-polarized current and a large magnetoresistance, i.e. the spin valve effect. These effects may be used for controlling spin transport in semiconducting nanostructures, e.g. spin transistors, spin-blockade devices etc., by variation of the intensity S and frequency ω of the external radiation

Collective excitations in carbon nanotubes

The effective action functional has been built by a functional integral method for nanotubes. The closed, self-consistent system of equations of the system is built on the basis of the variational differentiation the effective action on collective variables of an electron-phonon subsystem. A general expression for a polarization function and spectrum of the system are considered

Bound states in 2D fermion systems of graphen

Analytical solutions for the zero-energy modes of two-dimensional massless Dirac fermions confined within the one-dimensional Lorentz-like potential, which provides а reasonable fit for potential profiles of existing top-gated graphene structures is performed. On the basis of obtained hypergeometrical equations we have studied the conditions for formation of quantum bound states providing an one-dimensional fermion localization. А simple relations between the potential parameters and number of modes within the potential are established. Possibility of realization of the external controlled charge transport in the studied 2D system is considered