Novel Radiation-Induced Magnetoresistance Oscillations in a Nondegenerate Two-Dimensional Electron System on Liquid Helium

Abstract

We report the observation of novel magnetoresistance oscillations induced by the resonant intersubband absorption in nondegenerate 2D electrons bound to the surface of liquid 3 He. The oscillations are periodic in B −1 and originate from the scattering-mediated transitions of the excited electrons into the Landau levels of the first subband. The structure of the oscillations is affected by the collision broadening of the Landau levels and by many-electron effects.PACS numbers: 03.67.Lx, 73.25.+i, 78.70.Gq The dynamical response of a two-dimensional electron system (2DES) is strongly affected by the magnetic field applied perpendicular to the 2D plane. In particular, the Landau quantization of the electron energy for the inplane motion alters the transport properties of such systems and often results in oscillations of the electron magnetoresistivity. In degenerate 2DESs in semiconductors, the most well known example of such oscillations is the Shubnikov-de Haas oscillations arising from the sequential passing of Landau levels (LLs) through the Fermi level. Other examples include magnetointersubband oscillations in GaAs quantum wells [1] and microwaveinduced resistance oscillations (MIRO) in GaAs/AlGaAs heterostructures [2,3]. A novel type of resistance oscillation induced by resonant inter-subband absorption in nondegenerate 2DES is the subject of this Letter.Low-density classical 2D electrons formed on the surface of liquid helium are the complement of quantum 2DESs in semiconductors [4,5]. The difference in energy between subbands is small and inter-subband transitions can be excited with resonant millimeter-wave radiation [6]. At high temperatures, the electron in-plane transport is determined by the short-range quasi-elastic scattering from helium vapor atoms, which is similar to the scattering due to disorder in semiconductors. At low temperatures (below 0.3 K for 3 He), the scattering only occurs from surface capillary waves (ripplons). Unique correlation properties of 2DES are observed through the Wigner crystallization [7], quantum tunneling phenomena [8] and inter-subband absorption [9].At high temperatures, the magnetotransport of 2DES on helium is well described by an independent-electron theory based on the self-consistent Born approximation (SCBA) [10]. Below 1 K, the many-electron fluctuating electric field originating from the Coulomb interaction affects the electron scattering in both classically strong and quantizing magnetic fields. This was shown by Dykman et al., who presented a theory for both ripplon [11] and vapor atom scattering [12]. Many-electron effects have also been observed in quantum cyclotron resonance [13].Interest in this system also stems from the proposals for quantum computing using electrons on helium [14,15]. These proposals rely on the robust control of electronic quantum states using resonant microwaves. For such applications, microwave-induced inter-subband absorption has been recently studied for electrons on both liquid 4 He and liquid 3 He [16]. It was shown that ...

Theory of microwave-induced zero-resistance states in two-dimensional electron systems

“…(25) contains all the cyclotron harmonics, with the amplitude of the k-th term determined by the x-dependence of the electric field E x (x), Eq. (26). In the special case of R c → 0 [the field slowly varies at the cyclotron radius scale, Eq.…”

Coulombic effects on magnetoconductivity oscillations induced by microwave excitation in multisubband two-dimensional electron systems

“…This transition occurs when / 137 C U T [15]. Therefore, there is a broad range 1 / <137, C U T where the electron system represents a highly correlated Coulomb liquid. These conditions are quite usual for experiments on SEs in liquid helium.…”

“…Observation of microwave-resonance-induced magnetoconductivity oscillations in the multisubband twodimensional (2D) electron system formed on the free surface of liquid helium [1,2] have attracted much interest. These oscillations appear to be very similar to 1/B-periodic resistivity ( xx R ) oscillations observed in ultrahigh-mobility GaAs/AlGaAs heterostructures subjected to a dc magnetic field and to strong microwave (MW) radiation of a quite arbitrary frequency > c ω ω [3][4][5] (here c ω is the cyclotron frequency).…”

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

“…Both effects were totally unexpected when they were first obtained revealing some type of new radiation-matter interaction or coupling assisting electron magnetotransport [3][4][5]. Despite that over the last few years important experimental [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] and theoretical efforts [26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42] have been made on MIRO and ZRS, their physical origin still remains controversial and far from reaching a definite consensus among the people devoted to this field. For instance, the two, in principle, accepted theoretical models explaining MIRO, (displacement [31] and inelastic [35] models) are under question in regards of recent (and even older) experimental results [43,44] that they are not able to explain.…”