Interference Effects Of Electron Waves Research Articles

Magnetisation and magnetoresistance of Mo/Fe/Co superlattices

AbstractIn this paper, we present experimental studies of the structure, magnetic behavior and magnetoresistance of magnetic superlattices (MSL) [Mo(12Å)Fe(xÅ)Co(21Å)]*100 (x=4÷43). MSLs have been obtained by cathode sputtering with oscillating electrons on the substrate of mica (muscovite). MSLs investigated at room temperature are soft ferromagnets with induced in‐plane magnetic anisotropy. Changes in the spontaneous magnetization Iso and coercive force Hc, depending on the thickness of Co layers, are of oscillatory behavior, which is apparently because of the interference effects of electron waves in the spacers and interfaces. Stepped shape of the measured hysteresis loops for some MSLs, is apparently determined by the vortex behavior of the clusters magnetic moments, located in the sample plane, that is confirmed by measurements carried out on the scanning probe microscope. The observed high values of Iso, normalized to the content of Fe and Co, exceeding Iso(Fe)=1710 Gs may be observed due to increasing values of spin and orbital magnetic moments of Fe and Co in the cluster formations and in the interfaces in the states of low‐dimensional local atomic environment, as well as the possible formation of ferromagnetic order in Mo clusters. Studies of resistance and magnetoresistance (MR) of the samples at temperatures from 10 K to 290 K show semiconducting behavior of resistance and a positive sign of the magnetoresistance. The maximum value of MR for a sample of [Mo (12A) Fe (16A) Co (21A)] x100 was 0.04% for [Mo (12A) Fe (10A) Co (21A)]x100 ‐ 0.5%. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Coupling effects on the conductance fluctuations in GaAs/AlGaAs double quantum dots

Electron wave interference effects in GaAs/AlGaAs coupled quantum dots have been studied at 30 mK in magnetic fields with different coupling strength between two dots. In a strong coupling regime, the existence of global trajectories which span two dots was suggested, while in a weak coupling regime, the trajectories were found to be limited in each single dot.

Electron Wave Interference in Ballistic and Quasi-Ballistic Nanostructures

We have studied electron wave interference effects in wires and dots in ballistic and quasi-ballistic transport regimes, fabricated by using split gate, or wet etching techniques. We observe conductance fluctuations as a function of magnetic field, and we show they arise from the different origin of the scattering source for interference. It is shown experimentally that scatterings occur at the boundaries of the wall in the ballistic sample, while they occur at impurities in quasi-ballistic sample. This difference is clearly demonstrated in the temperature dependence of the fluctuation amplitude and the shape dependent negative magnetoresistance peak due to the weak localization effect. We discuss also the phase breaking time in a ballistic dot, which is very important for the interference.

Numerical analysis of electron-wave detection by a wedge-shaped point contact.

To investigate useful properties caused by various interference effects of electron waves in a mesoscopic system, we carry out a numerical analysis of electron-wave propagation by a combination of several techniques for solving the two-dimensional Schr\odinger equation. The techniques provide an accurate solution for a realistic potential profile in a point-contact structure, and are simple to apply even under magnetic fields. By using this calculation method, we investigate the detection of the propagation from a quantum point-contact injector to a point-contact detector under magnetic fields. We calculate electron-wave propagation and transfer conductance through a wedge-shaped detector, which has a smaller scattering cross section for injected electron waves than ordinary line-shaped detectors, and analyze the interference due to the detector as a function of detector parameters. We conclude that a well-designed wedge-shaped point contact could provide good detection of electron-wave propagation.

Conductance fluctuations in a quasi-ballistic narrow wire confined by split metal gates

Analysing the conductance fluctuations observed in low-temperature magnetoresistance, we study electron wave interference effects in the quasi-ballistic transport regime of a narrow wire, defined by split metal gates, on the two-dimensional electron gas of a GaAs/AlGaAs heterojunction. There is a clear difference in the conductance fluctuations between short and long wires of 2 and 6 μm gate length, respectively. Such a difference can be explained by considering whether some correlated channels exist in the wire or not.

Numerical study of the interference effects of electron waves scattered by impurities or slits in a quasi-one-dimensional system.

We present a useful numerical method of investigating the electron conduction through a region where the obstacles are placed in a quasi-one-dimensional system. Using this method, we have studied the interference effects of electron waves scattered by obstacles such as impurities. Electron conduction through slits in a quantum wire has also been investigated, and it has been found that the conductance is heavily modulated by the interference among the incident wave and electron waves scattered by the edges and potential barriers.

Electron wave interference effects in CMT and quantum-size devices

The authors report on electron interference effects in n-Hg0.8Cd0.2Te (CMT). This narrow-gap semiconductor has a very light effective electron mass and a comparatively long electron wave coherence length. Due to these properties a non-classical conductivity was observed in bulk samples at elevated temperatures up to 35 K. Dimensional crossovers were discovered in samples as large as 1*2.5* 35 mu m3: with decreasing temperature size-quantization from three- via two- to one-dimensional behaviour takes place. The evidence of pronounced electron wave interference effects favours CMT as a candidate for novel quantum size devices, as cutoff wavelength transistors or quantum-valve infrared detectors.

Ballistic electron emission testing of semiconductor heterostructures

In ballistic electron emission microscopy (BEEM) and spectroscopy, ballistic electrons are injected into a sample using a scanning tunneling microscope to probe the electrical properties of buried interfaces. In this communication, a method is proposed that uses the BEEM technique to observe the electron wave optical properties of semiconductor heterostructures. This method provides a three-terminal configuration for characterizing electron wave devices that overcomes many of the limitations encountered in other two- and three-terminal measurement techniques. Specifically, the method provides an injector, which is well isolated from the heterostructure, that injects a collimated beam of ballistic carriers with a precisely controlled energy distribution. These carriers accurately probe the quantum transmittance of a voltage-tunable electron wave interference structure, which can be designed with a light doping to minimize impurity and electron-electron scattering. A general procedure is presented for analyzing this experimental configuration based on a combination of the models used to describe BEEM and ballistic electron transport in semiconductors. Using this procedure, BEEM testing of an electron wave energy filter is modeled and clear quantum interference effects are predicted. This BEEM configuration should allow for the precise characterization of a wide range of ballastic electron transport effects such as quantum reflections from interfaces and electron wave interference effects, phenomena that are presently of wide interest.