Magnetoplasmons in a Tunable Periodically Modulated Magnetic Field

Abstract

We report the first infrared optical measurements of a two dimensional electron gas (2DEG) in a periodically modulated magnetic field. The 2DEG is produced using epitaxial regrowth on a corrugated surface, so that the component of an externally applied magnetic field perpendicular to the 2DEG is spatially modulated. Two active modes are observed, with intensities and frequencies which depend on the amplitude of the field modulation as well as the total external magnetic field. These modes arise from field modulation-induced coupling between the 2DEG magnetoplasmons. Calculations of the magnetoplasmon band structure in a modulated field are in excellent agreement with the experimental data. 73.20.At, 73.20.Mf Band structure effects arising from periodic modulations can be observed in a wide range of a physical systems. Electron energy bands produced by the periodic potential in a crystal, photonic band structures in systems with periodic dielectric constants, and plasmons in charge density modulated systems, are just some examples of systems in which mode dispersions show energy gaps at the edges of the Brillouin zone due to a periodic modulation. The effects of periodic electrostatic potentials on a two dimensional electron gas (2DEG) have been extensively studied theoretically and experimentally [1], and there is now increasing interest [2][3][4][5][6][7][8][9][10][11][12] in the effects produced by a novel form of periodic potential-that produced by a periodically modulated magnetic field (PMMF).PMMF investigations to date have been largely theoretical. It has been predicted that the sharp Landau levels produced in the presence of a uniform perpendicular magnetic field become broadened by introducing a small periodic component B m , and the width oscillates with B [3]. At very low magnetic fields, when the period d of the modulation is comparable with the cyclotron radius R c , so-called commensurability oscillations are expected, and a series of subsingularities (van Hove singularities) at the edges of the broadened Landau levels appear [9], which should produce splittings of the cyclotron resonance (CR). For R c ø d, new magnetoplasmon (MP) modes arising from the PMMF have been predicted theoretically [4,9,12], and variations in the electron wave function are expected to change the local occupancy of the Landau levels, producing a modulation in the local electron density [4,11]. In the presence of large magnetic field modulations, this effect should produce a transition from a modulated 2DEG to an array of isolated wires [4].Few of these theoretical predictions have been verified, with experimental data confined to d.c. transport measurements of commensurability oscillations in which the PMMF was produced by evaporating stripes of either superconducting or ferromagnetic materials on top of the 2DEG [6,8,10]. But experimental observations of the optical properties of a 2DEG in a PMMF have yet to be reported.Here we report the first optical measurements on a 2DEG in the presence of a PMMF. We have investiga...

Magnetoplasmons in gapped graphene in a periodically modulated magnetic field

“… (theory) (experiment), similar to Ref. for the C2DEG. A modulated electric field in graphene was created and Weiss oscillations were observed in Refs.…”

“…Single particle magneto‐oscillatory phenomena, such as the Shubnikov‐de Haas (SdH) and de Haas‐van Alphen effects, are important probes for the electronic structure of solids and their collective analogs yield insights into collective phenomena . However, the effect of a periodically modulated magnetic field has not been studied so far, whereas magnetoplasmons in a conventional two‐dimensional electron gas (C2DEG) have been investigated extensively experimentally and theoretically . The far‐infrared absorption spectrum has been studied theoretically to explore the plasma oscillations and magnetic modulation effects have been the subject of quantum magnetotransport experiments and theory .…”

Electronic structure of a two-dimensional graphene monolayer in a spatially modulated magnetic field: Peierls tight-binding model

“…These works primarily analyze the transport properties, [24][25][26]28,29 energy bands, 30-32 electronic excitations, [33][34][35][36] and optical spectra. 27 The transport measurements 24,25 manifest the oscillatory magnetoresistance. Energy bands of a 2DEG have parabolic energy dispersions.…”

“…There have been numerous experimental [24][25][26][27] and theoretical [28][29][30][31][32][33][34][35][36] research for a two-dimensional electron gas ͑2DEG͒ under a spatially modulated magnetic field. These works primarily analyze the transport properties, [24][25][26]28,29 energy bands, 30-32 electronic excitations, [33][34][35][36] and optical spectra.…”

Plasmonic Modes in Thin Films: Quo Vadis?

“…The comprehension of plasmonic excitations in thin films (Chiarello et al, 1997a,b), especially of noble metals Politano, 2012aPolitano, ,b, 2013 and graphene (Politano et al, 2011(Politano et al, ,b, 2013aCupolillo et al, 2012Cupolillo et al, , 2013aChiarello, 2013a,b, 2014), could keep active researchers for a long time.…”