Series of magnetoresistance oscillations of a two-dimensional electron gasin a strong periodic magnetic modulation

Abstract

A nonperturbative technique is used to calculate the magnetoresistance of two-dimensional electron gases ͑2DEG͒ subjected to a spatially periodic magnetic field B 1 with period a in addition to a uniform magnetic field B 0 in the same direction. For small amplitude modulation, magnetoresistance exhibits oscillations similar to the Weiss oscillations observed in 2DEG under spatially periodic electric field and uniform magnetic field. In general, the oscillation is characterized by two ratios: ␤ϭ2l/a and ␥ϭB 1 /B 0 , at low magnetic modulations, with l being the magnetic length corresponding to B 0 . Quenching of Weiss oscillations first appears as ␥ increases for fixed B 0 , and a series of oscillations then appears in our nonperturbative calculation for larger ␥. The temperature dependence of these oscillations shows that the basic mechanism of the production of these oscillations is similar to the Weiss oscillations. ͓S0163-1829͑97͒06307-8͔

Magnetoplasmons in a Tunable Periodically Modulated Magnetic Field

“…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.…”

“…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].…”

“…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.…”

Angle-dependent Weiss oscillations in a nanocorrugated two-dimensional electron gas

“…Therefore, we will only account for the diffusional part of the dc conduction in our system. We emphasize that previous works on conventional 2DEG subject to additional modulated magnetic fields have accounted only for the diagonal diffusion contribution to the dc conductance [36,37,39]. This is a well justified assumption considering a magnetic modulation weak as compared to the external homogeneous magnetic field.…”

Energy spectrum of Bloch electrons with two-dimensional magnetic flux modulation

“…In these 2DEG's, one observes interesting magnetotransport phenomena even at moderate magnetic fields, leading to a renewal of interest in the subject. [6][7][8][9][10][11][12] Some recent highlights are the Weiss oscillations, 6 which is an oscillatory magnetoresistance observed in weak magnetic fields, the transport experiments that reveal some signs of the butterfly [13][14][15] in a twodimensional electric potential modulation system, and the symmetry breakings found in the theoretical studies of the energy spectrum of Bloch electrons under one-dimensional magnetic modulation by Gumbs et al 16 To pursue the signitures of the Hofstadter spectrum, we study the energy spectrum of Bloch electrons under two-dimensional magnetic flux modulation with a magnetic field B ជ ϭ͓B 0 ϩ(Ϫ) mϪn B 1 ͔ẑ going through the (m,n) plaquette where r ជ ϭmax ϩnaŷ also labels the lower left-hand corner of the plaquette. Here B 0 is the uniform field and B 1 is the two-dimensional modulating field.…”