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We investigate the para-quantum extension of the bosonic strings in a non-commutative space-time. We calculate the trilinear relations between the mass-center variables and the modes and we derive the Virasoro algebra where a new anomaly term due to the non-commutativity is obtained. [ABSTRACT FROM AUTHOR]

Transport measurements in a quasi-one dimensional (1D) quantum wire are reported in the presence of low transverse magnetic field. Differential conductance shows weak quantised plateaus when the 2D electrons are squeezed electrostatically. Application of a small transverse magnetic field (0.2T) enhances the overall degree of quantisation due to the formation of magneto-electric subbands. The results show the role of magnetic field to fine tune the confinement strength in low density wires when interaction gives rise to double row formation. [ABSTRACT FROM AUTHOR]

The size quantization effect is noticed as a shift of the transition energies toward higher values with decreasing particle size. Based on the SEM images report a curve is drawn and fitted with MATLAB programming to obtain a relation between excitonic absorbance and diameter of the nano crystal. Nonlinear fit of the curve is used to provide an empirical formula for the estimation of the excitonic absorbance as a dependent parameter of diameter of nano crystal. Some adjustable parameter is required to calculate the excitonic absorbance wavelength of CdSe nano crystal. Theoretical findings are graphically represented and compared with available experimental results. The theoretical model predicts a decrease in absorbance wavelength or blue shift in absorbance spectrum which consequently increases the band gap of CdSe nano crystal with decreasing of crystalline sizes. Results are comparable with the established experimental findings. [ABSTRACT FROM AUTHOR]

We have investigated lateral electron tunneling through single self-assembled InAs quantum dashes (QDHs) coupled to metallic nanogap electrodes. Coulomb stability diagram of the QDH/electrode system exhibits clear diamond patterns, reflecting single electron tunneling. We have observed novel electronic states and high differential conductance, intrinsic to InAs QDH structures with a highly asymmetric shape. From the size of the Coulomb diamonds for N>10, the charging energy EC and the orbital quantization energy ΔE of the system are estimated to be EC∼1-2 meV and ΔE∼1-2 meV, respectively. These results indicate that single electron transistors with low junction resistance as well as small EC and ΔE, favorable for realizing supercurrent transistors, are available by using InAs QDH structures. [ABSTRACT FROM AUTHOR]

Usually heating of conducting electrons by dc electric field results in an increase of electron temperature. In this paper we show that the dc heating of 2D electrons, placed in quantized magnetic fields, results in a peculiar electron distribution, which has the same broadening or an effective 'temperature' as the unbiased electron system. The quantal heating, however, violates strongly the Ohm's Law. In the conducting system with discrete electron spectrum the quantal heating results in spectacular decrease of electron resistance and transition of the electrons into a state with zero differential resistance (ZDR). Finally the heating leads to apparent dc driven metal-insulator transition, which correlates with the transition into the ZDR state. The correlation is very unexpected and is not understood. [ABSTRACT FROM AUTHOR]

The present status of our studies of thickness oscillations of the transport properties in IV-VI quantum wells is reviewed. The results of those studies provide the first experimental evidence for the existence of oscillations in the thickness dependences of the transport properties of IV-VI quantum wells caused by size quantization of the electron (hole) energy spectrum. [ABSTRACT FROM AUTHOR]

We report the experimental observation of magnetically bound electronic states in a quantum wire with a magnetic barrier, as a function of a superimposed homogeneous perpendicular magnetic field which displaces the magnetic barrier along the magnetic field axis. [ABSTRACT FROM AUTHOR]

We investigate a recently developed scheme for quantized charge pumping based on single-parameter modulation. The device was realized in an AlGaAl-GaAs gated nanowire. It has been shown theoretically that non-adiabaticity is fundamentally required to realize single-parameter pumping, while in previous multi-parameter pumping schemes it caused unwanted and less controllable currents. In this paper we demonstrate experimentally the constructive and destructive role of non-adiabaticity by analysing the pumping current over a broad frequency range. [ABSTRACT FROM AUTHOR]

The quantization of conductance in units of 2e2/h of a quantum point contact (QPC) under low temperature, a narrow way formed in a two-dimensional electron gas (2DEG), has become a paradigm of mesoscopic physics. Devices defined by electrostatic gates in GaAs/AlGaAs 2DEGs display an extraordinary variety of spin related phenomena. Besides the usual conductance plateaus, QPCs show an extra plateau at ∼0.7 (2e2/h), believed to arise from electron-electron interactions. These plateaus disappear as temperature rise. We present the experimental results of temperature dependent disappearance. Under magnetic fields plateaus shift due to the Landau level. The numerical results using Green's function approach is also presented. [ABSTRACT FROM AUTHOR]

We have measured thermoelectric power in unidirectional lateral superlattices (ULSLs). The oscillations due to the Landau quantization in the longitudinal thermoelectric power Sxx exhibit marked amplitude modulation, analogous to but more pronounced than the amplitude modulation of the Shubnikov-de Haas oscillations in the resistivity ρxx. The semiclassical commensurability oscillations are not evident in Sxx, but are expected to be more apparent in the transverse component with the temperature gradient applied perpendicular to the principal axis of ULSLs, underlining the qualitative difference between the resistivity and the thermoelectric power in the way the anisotropy manifests itself. [ABSTRACT FROM AUTHOR]