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Register a new userInducement and suppression of Coulomb effects in elastic 2D-2D electron tunnelling in a quantizing magnetic field
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Tunnelling between two-dimensional electron systems has been studied in the magnetic field perpendicular to the systems planes. The satellite conductance peaks of the main resonance have been observed due to the electron tunnelling assisted by the elastic scattering on impurities in the barrier layer. These peaks are shown to shift to the higher voltage due to the Coulomb pseudogap in the intermediate fields. In the high magnetic fields the pseudogap shift is disappeared.
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The electron tunneling is experimentally studied between two-dimensional electron gases (2DEGs) formed in a single-doped-barrier heterostructure in the magnetic fields directed perpendicular to the 2DEGs planes. It is well known that the quantizing magnetic field induces the Coulomb pseudogap suppressing the electron tunneling at Fermi level. In this paper we firstly present the experimental results revealing the pseudogap in the electron tunneling assisted by elastic electron scattering on disorder.
The lifetime of two dimensional electrons in GaAs quantum wells, placed in weak quantizing magnetic fields, is measured using a simple transport method in broad range of temperatures from 0.3 K to 20 K. The temperature variations of the electron lifetime are found to be in good agreement with conventional theory of electron-electron scattering in 2D systems.
We present a variety of methods to derive the Casimir interaction in planar systems containing two-dimensional layers. Examples where this can be of use is graphene, graphene-like layers and two-dimensional electron gases. We present results for two free standing layers and for one layer above a substrate. The results can easily be extended to systems with a larger number of layers.
Magnetic field suppression of the tunneling between disordered 2D electron systems in GaAs around zero bias voltage has been studied. Magnetic field B normal to the layers induces a dip in the tunneling density of states (TDOS) centered precisely at the Fermi level, i.e. soft tunneling gap. The soft gap has a linear form with finite TDOS diminishing with B at the Fermi level. Driven by magnetic field the transition soft-hard gap has been observed, i.e. the TDOS vanishes in the finite energy window around Fermi level at B>13 T.
We consider a clean two-dimensional interacting electron gas subject to a random perpendicular magnetic field, h({bf r}). The field is nonquantizing, in the sense, that {cal N}_h-a typical flux into the area lambda_{text{tiny F}}^2 in the units of the flux quantum (lambda_{text{tiny F}} is the de Broglie wavelength) is small, {cal N}_hll 1. If the spacial scale, xi, of change of h({bf r}) is much larger than lambda_{text{tiny F}}, the electrons move along semiclassical trajectories. We demonstrate that a weak field-induced curving of the trajectories affects the interaction-induced electron lifetime in a singular fashion: it gives rise to the correction to the lifetime with a very sharp energy dependence. The correction persists within the interval omega sim omega_0= E_{text{tiny F}}{cal N}_h^{2/3} much smaller than the Fermi energy, E_{text{tiny F}}. It emerges in the third order in the interaction strength; the underlying physics is that a small phase volume sim (omega/E_{text{tiny F}})^{1/2} for scattering processes, involving {em two} electron-hole pairs, is suppressed by curving. Even more surprising effect that we find is that {em disorder-averaged} interaction correction to the density of states, delta u(omega), exhibits {em oscillatory} behavior, periodic in bigl(omega/omega_0bigr)^{3/2}. In our calculations of interaction corrections random field is incorporated via the phases of the Green functions in the coordinate space. We discuss the relevance of the new low-energy scale for realizations of a smooth random field in composite fermions and in disordered phase of spin-fermion model of ferromagnetic quantum criticality.
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