Radiation-induced resistance oscillations in a 2D hole gas: a demonstration of a universal effect

We report on a theoretical insight about the microwave-induced resistance oscillations and zero resistance states when dealing with p-type semiconductors and holes instead of electrons. We consider a high-mobility two-dimensional hole gas hosted in a pure Ge/SiGe quantum well. Similarly to electrons we obtain radiation-induce resistance oscillations and zero resistance states. We analytically deduce a universal expression for the irradiated magnetoresistance, explaining the origin of the minima positions and their $1/4$ cycle phase shift. The outcome is that these phenomena are universal and only depend on radiation and cyclotron frequencies. We also study the possibility of having simultaneously two different carriers driven by radiation: light and heavy holes. As a result the calculated magnetoresistance reveals an interference profile due to the different effective masses of the two types of carriers.Comment: 9 pages and 9 figure

Fourier transform analysis of irradiated Weiss oscillations

We present a theoretical approach to study the effect of microwave radiation on the magnetoresistance of a one-dimensional superlattice. In our proposal the magnetoresistance of a unidirectional spatial periodic potential (superlattice), is modulated by microwave radiation due to an interference effect between both, space and time-dependent potentials. The final magnetoresistance will mainly depend on the spatial period of the superlattice and the radiation frequency. %Then, by tuning either the spatial period of the superlattice or the radiation %frequency, the magnetoresistance can be strongly modified. We consider an approach to study these effects based on the fast Fourier transform of the obtained magnetorresistance profiles in function of the inverse of the magnetic field. Based on this theory we propose the design of a novel radiation sensor for the Terahertz band.} % We first study the FFT of the system for each potential individually. Then we study jointly the FFT of the system when the two types of potentials are simultaneously acting.Comment: 5 pages, 6 figures. arXiv admin note: substantial text overlap with arXiv:0808.237

Effect of frequency and temperature on microwave-induced magnetoresistance oscillations in two-dimensional electron systems

Experimental results on microwave-induced magnetoresistance oscillation in two-dimensional electron systems show a similar behavior of these systems regarding temperature and microwave frequency. It is found that these oscillations tend to quench when frequency or temperature increase, approaching magnetoresistance to the response of the dark system. In this work we show that this experimental behavior can be addressed on the same theoretical basis. Microwave radiation forces the electron orbits to move back and forth being damped by interaction with the lattice. We show that this damping depends dramatically on microwave frequency and also on temperature. An increase in frequency or temperature gives rise to an increase in the lattice damping producing eventually a quenching effect in the magnetoresistance oscillations.Comment: 3 pages and 3 figure

Hall magnetoresistivity response under Microwave excitation revisited

We theoretically analyzed the microwave-induced modification of the Hall magnetoresistivity in high mobility two-dimensional electron systems. These systems present diagonal magnetoresistivity oscillations and zero-resistance states when are subjected to microwave radiation. The most surprising modification of the Hall magnetoresistivity is a periodic reduction which correlates with a periodic increase in the diagonal resistivity. We present a model that explains the experimental results considering that radiation affects directly only the diagonal resistivity and the observed Hall resistivity changes are coming from the tensor relationship between both of them.Comment: 3 pages, 2 figure

High-temperature observation and power modulation of radiation-induced resistance oscillations in the terahertz band

We report on a theoretical work on magnetotransport under terahertz radiation with high-mobility two-dimensional electron systems focussing on the radiation power and temperature dependence. On the one hand, we study the interaction between the obtained radiation-induced magnetoresistance oscillations (RIRO) and the Shubnikov-de Haas oscillations (SdHO) from the power dependence standpoint. We obtain strong modulation of the SdHO at sufficient terahertz radiation power. On the other hand from the temperature dependence standpoint we obtain an important result: the range of temperature where RIRO are observed can be largely extended by using terahertz radiation. In the terahertz region we still obtain RIRO up to 20K at a radiation frequency of 400GHz. Since an increasing T gives rise in turn to more disorder in the sample, we would expect also the observation of RIRO with terahertz radiation when using low-mobility (high-disorder) samples at low T.This work is supported by the MINECO (Spain) under grant MAT2014-58241-P and ITN Grant 234970 (EU), Grupo de Matematicas Aplicadas a la Materia Condensada, (UC3M), Unidad Asociada al CSIC

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

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 pi . 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.This work is supported by the MINECO (Spain) under grant MAT2017-86717-P and ITN Grant 234970 (EU). Grupo de Matematicas aplicadas ala Materia Condensada, (UC3M), Unidad Asociada al CSIC

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

We provide the ultimate explanation of one of the core features of microwave-induced magnetoresistance oscillations in high-mobility two-dimensional electron systems: the 1/4-cycle phase shift of minima. We start with the radiation-driven electron orbits model with the novel concept of scattering flight-time between Landau states. We calculate the extrema and nodes positions obtaining an exact coincidence with the experimental ones. The main finding is that the physical origin of the phase shift is a delay of pi/2 of the radiation-driven Landau guiding center with respect to radiation, demonstrating the oscillating nature of the irradiated Landau states. We analyze the dependence of this minima on radiation frequency and power and its possible shift with the quality of the sample.This work is supported by the MINECO (Spain) under grant MAT2014-58241-P and ITN Grant 234970 (EU), Grupo de Matematicas Aplicadas a la Materia Condensada, (UC3M), Unidad Asociada al CSIC

Microscopic theory for radiation-induced zero-resistance states in 2D electron systems: Franck-Condon blockade

We present a microscopic model on radiation-induced zero resistance states according to a novel approach: Franck-Condon physics and blockade. Zero resistance states rise up from radiation-induced magnetoresistance oscillations when the light intensity is strong enough. The theory begins with the radiation-driven electron orbit model that proposes an interplay of the swinging nature of the radiation-driven Landau states and the presence of charged impurity scattering. When the intensity of radiation is high enough, the driven-Landau states (vibrational states) involved in the scattering process are spatially far from each other and the corresponding electron wave functions no longer overlap. As a result, a drastic suppression of the scattering probability takes place and current and magnetoresistance exponentially drop. Finally, zero resistance states rise up. This is an application to magnetotransport in two-dimensional electron systems of the Franck-Condon blockade, based on the Franck-Condon physics which in turn stems from molecular vibrational spectroscopy. Published by AIP Publishing

Terahertz-induced oscillations in encapsulated graphene

A theoretical study on the rise of photo-oscillations in the magnetoresistance of hexagonal boron nitride (hBN)-encapsulated graphene is presented. The previous radiation-driven electron orbit model devised to study the same oscillations, well-known as MIRO, in 2D semiconductor systems (GaAs/AlGaAS heterostructure) is used. It is obtained that these graphene platforms under radiation and a static magnetic field are sensitive to terahertz and far-infrared radiation. The power, temperature, and frequency dependences of the photo-oscillations are studied. For power dependence, it is predicted that for cleaner graphene and high enough power it is possible to observe zero-resistance states and a resonance peak.This work is supported by the MINECO (Spain) under grant PID2020-117787GB-I00 and by the Madrid Government (Comunidad de Madrid-Spain) under the Multiannual Agreement with UC3M in the line of Excellence of University Professors (EPUC3M14), and in the context of the V PRICIT (Regional Programme of Research and Technological Innovation). We also acknowledge the CSIC Research Platform on Quantum Technologies PTI-00

Radiation-induced magnetoresistance oscillations with massive Dirac fermions

We Report On A Theoretical Study On The Rise Of Radiation-Induced Magnetoresistance Oscillations In Two-Dimensional (2d) Systems Of Massive Dirac Fermions.We Study The Bilayer System Of Monolayer Graphene And Hexagonal Boron Nitride (H-Bn/Graphene) And The Trilayer System Of Hexagonal Boron Nitride Encapsulated Graphene (H-Bn/Graphene/H-Bn).We Extend The Radiation-Driven Electron Orbit Model That Was Previously Devised To Study The Same Oscillations In 2d Systems Of Schrödinger Electrons (Gaas/Algaas Heterostructure) To The Case Of Massive Dirac Fermions. In The Simulations We Obtain Clear Oscillations For Radiation Frequencies In The Terahertz And Far-Infrared Bands.We Investigate Also The Power And Temperatures Dependence. For The Former We Obtain Similar Results As For Schrödinger Electrons And Predict The Rise Of Zero Resistance States. For The Latter We Obtain A Similar Qualitatively Dependence But Quantitatively Different When Increasing Temperature. While In Gaas The Oscillations Are Wiped Out In A Few Degrees, Interestingly Enough, For Massive Dirac Fermions, We Obtain Observable Oscillations For Temperatures Above 100 K And Even At Room Temperature For The Higher Frequencies Used In The Simulations.This work is supported by the MINECO (Spain) under Grant MAT2017-86717-P and ITN Grant 234970 (EU). Grupo de matematicas aplicadas a la materia condensada, (UC3M), Unidad Asociada al CSIC