Evidence of radiation-driven Landau states in 2D electron systems: Magnetoresistance oscillations phase shift

Applied Physics Letters

2018

We present a microscopic theory on the observation of a beating pattern in the radiation-induced magnetoresistance oscillations at very low magnetic field. We consider that such a beating pattern develops as a result of the coupling between two oscillatory components: the first is a system of electron Landau states being harmonically driven by radiation. The second is a lattice oscillation, i.e., an acoustic phonon mode. We analyze the dependence of the beating pattern on temperature, radiation frequency and power. We conclude that the beating pattern is an evidence of the radiation-driven nature of the irradiated Landau states that makes them behave as a collective plasma oscillation at the radiation frequency. Thus, the frequency of such plasmons could be tuned from microwave to terahertz in the same nanodevice with an apparent technological application. PACS numbers:Beating patterns show up when there are two oscillatory contributions coexisting and coupled in the same physical system. For instance, beating patterns can be observed in magnetoresistance (R xx ) of two-dimensional electron systems (2DES) when there are two populated conduction electron subbands involved in the transport. This situation gives rise to the well-known magneto-intersubband scattering oscillations (MISO) 1,2 . They can also be obtained in R xx of 2DES with strong Rashba spin-orbit coupling 3,4 . For both cases the two oscillatory subsystems are the two sets of broadened Landau levels of slightly different energies. On the other hand, two important physical effects in magnetotransport of 2DES

mentioning

confidence: 99%

Beating pattern in radiation-induced oscillatory magnetoresistance in 2DES: Coupling of plasmon-like and acoustic phonon modes

Applied Physics Letters

2018

“…With the expression of X ( t ) (Equation ) and according to the radiation‐driven electron orbit model, we obtain for the average distance advanced by the electron in a scattering event

\begin{array}{c} center & Δ X (t) = Δ X_{0} - e^{- \frac{γ}{2} τ} A [\sin ω_{+} τ + \sin ω_{-} τ] \\ center & = Δ X_{0} - 2 A e^{- \frac{γ}{2} τ} \sin ω τ \cos normalλ τ \end{array}

where we have used the well‐known expression:

\sin true(θ_{1} true) + \sin true(θ_{2} true) = 2 \sin true[\frac{θ_{1} + θ_{2}}{2} true] \cos true[\frac{θ_{1} - θ_{2}}{2} true]

and we have considered that

A ≃ B

and that

ω_{\pm} ≃ ω \pm λ

. The time,

τ

, according to the radiation driven electron orbit model, is the “flight time,” the time it takes the electron to jump due to scattering from one orbit to another and its value is given by

τ = \frac{2 π}{ω_{c}}

. Finally and following the radiation‐driven electron orbit model we end up with an expression for R xx :

R_{x x} \propto Δ X_{0} - 2 A e^{- π \frac{γ}{w_{c}}} \sin true(2 π \frac{ω}{ω_{c}} true) \cos true(2

…”

Section: Theoretical Modelmentioning

confidence: 99%

“…The time,

τ

, according to the radiation driven electron orbit model, is the “flight time,” the time it takes the electron to jump due to scattering from one orbit to another and its value is given by

τ = \frac{2 π}{ω_{c}}

. Finally and following the radiation‐driven electron orbit model we end up with an expression for R xx :

R_{x x} \propto Δ X_{0} - 2 A e^{- π \frac{γ}{w_{c}}} \sin true(2 π \frac{ω}{ω_{c}} true) \cos true(2 π \frac{λ}{ω_{c}} true)

…”

Section: Theoretical Modelmentioning

confidence: 99%

Plasmon–Phonon Coupling in Radiation‐Induced Resistance Oscillations: Beating Pattern and Phase Reversal

Physica Status Solidi (b)

2019

Self Cite

This article presents a theoretical study on the experimental observation of two different kinds of beating patterns in the microwave-induced resistance oscillations at very low magnetic field in a high mobility two-dimensional electron system. In the first pattern there was no phase reversal through the beat, however, the latter experiments present a clear phase reversal of π. Based on a model that considers that the beating pattern is produced as a result of the coupling between a system of electron Landau states harmonically driven by radiation and an acoustic phonon mode, the contradictory results are explained through a different intensity coupling in terms of amplitude. In the scenario of the non-phase-reversal case, the dependence on radiation frequency and temperature is studied as well as the possibility of observation of more than one beat by lowering temperature and microwave power. It is concluded that both results can be explained with the same theoretical model that in turn is based on the microwave-driven electron orbit model that was previously developed to explain microwave-induced resistance oscillations.however the latter [33] presents a phase reversal of π. In this article we try to explain this apparent contradictory behavior based on

“…If now we switch on radiation, first of all we have to add to the Hamiltonian H 0 a radiation term H R and then: H 0 = ( H B + H SO + H R ), where ε 0 being the radiation electric field and w the corresponding radiation frequency. H 0 can again be solved exactly 20 , 21 , 51 , 52 , and the solution for the electronic wave function is made up, as above, of two states branches. The wave function for the + branch is, and for the - branch, where, as above, Φ n is the solution for the Schrödinger equation of the unforced quantum harmonic oscillator where x cl ( t ) is the classical solution of a forced harmonic oscillator 20 , 51 , 52 , where e is the magnitude of the electron charge and γ is a phenomenologically introduced damping factor for the electronic interaction with acoustic phonons.…”

Section: Theoretical Modelmentioning

confidence: 99%

Radiation-induced resistance oscillations in 2D electron systems with strong Rashba coupling

2017

Sci Rep

Self Cite

We present a theoretical study on the effect of radiation on the mangetoresistance of two-dimensional electron systems with strong Rashba spint-orbit coupling. We want to study the interplay between two well-known effects in these electron systems: the radiation-induced resistance oscillations and the typical beating pattern of systems with intense Rashba interaction. We analytically derive an exact solution for the electron wave function corresponding to a total Hamiltonian with Rashba and radiation terms. We consider a perturbation treatment for elastic scattering due to charged impurities to finally obtain the magnetoresistance of the system. Without radiation we recover a beating pattern in the amplitude of the Shubnikov de Hass oscillations: a set of nodes and antinodes in the magnetoresistance. In the presence of radiation this beating pattern is strongly modified following the profile of radiation-induced magnetoresistance oscillations. We study their dependence on intensity and frequency of radiation, including the teraherzt regime. The obtained results could be of interest for magnetotransport of nonideal Dirac fermions in 3D topological insulators subjected to radiation.