Width Of Potential Well Research Articles

Resonant tunnelling of wave packet

This paper examines tunnelling through potential well protected by double barriers as well as the motion of a wave packet encountering this type of potential. Various options for the left and right barriers’ penetration factors are taken into consideration. When one of the penetration factors has limiting value of 0.5, the transmission coefficients turns out to be independent of incoming energy of the particle and the width of potential well. When both penetration factors have a limiting value of 0.5, a scenario similar to resonance tunneling is achieved. Furthermore, by doing the wave packet analysis, we found that the width and height of potential barriers have a negligible impact on the probability of finding the particle inside the potential well in the limit of large penetration factors.

Two-dimensional electron gas in piezotronic devices

Recent developments of piezotronic devices start to focus on the quantum behaviors of the nanostructured system going beyond the conventional device applications. Piezotronic devices utilize piezoelectric field to control the charge carrier behaviors at the junction, contact or interface of piezoelectric semiconductor, such as ZnO, GaN, and two-dimensional materials. In this study, we theoretically investigate the piezoelectric field effect on two-dimensional electron gas (2DEG) in AlGaN/GaN heterostructure by employing an approximate triangular potential model. Basic electronic properties such as wave function, electronic energy, electronic density distribution and the width of potential well are explored under the influence of the externally applied strain. From the electronic density, bound state can be eliminated or created by properly changing the external strain, meaning the effective modulation of piezotronic effect on quantum states. The piezoelectric field in 2DEG system is perpendicular to the electronic transport, which has remarkable advantage over the parallel case in switching devices. Furthermore, piezoelectric modulation of intrasubband transition enriches the fundamental theory of piezo-photonics and provides guidance for designing strain-gated infrared devices.

A method of calculating and analyzing wear rate of materials under fretting condition

Fretting phenomena exist widely in structural engineering. In recent years, it has attracted more attention from scientists and technicians. In order to study the fretting wear in depth, we establish a new method of calculating the wear rate of material in vibratory environment. Firstly, according to the characteristics of friction pair and fretting wear process in fretting friction system, the asymmetric double potential well model is proposed and the potential energy function of the model is given. The transfer of particles between the two kinds of materials during the fretting is regarded as the motion of the particles in the two potential wells which are asymmetrical, and the particle motion equation in the potential well is established. Furthermore, considering the characteristics of the randomness, time-varying and irreversibility of particle motion in fretting friction system, a theoretical model is established by using the non-equilibrium statistical theory, which is based on the particle equation motion, combined with the Langevin equation in random theory and the Foker-Planck equation in the non-equilibrium statistical theory. The probability density distribution function of particles moving from the interior of the material to the material surface at any time is obtained. A method of calculating the wear rate is proposed by integrating the probability density distribution function. Secondly, by calculating the wear rate of the friction pair which consists of metal materials Mg and Fe, we obtain the potential energy function of the asymmetric double potential well model as the different surface energies of both materials. Furthermore, the probability density distribution function of particles moving in this friction pair is calculated. Then, the change of wear rate with wear time and width of potential well is derived, and the effect of normal force on wear rate is further analyzed. The results of calculation and analysis show that the wear rate of material decreases with the decrease of the width of the potential well in the friction pair system, decreases with the increase of wear time and increases with the increase of the normal force of the load, and the surface of the relatively soft material in the friction pair system is more likely to wear off. Finally, the conclusions of the theoretical model accord with the experimental results, illustrating the applicability of the theoretical model.

Voltage-tunable group delay of an electron wave packet through a single quantum potential well

It is shown that the group delay of an electron wave packet through a potential well can be either negative or positive and is tunable by finite electric fields. The group delay depends not only on the width of potential well and the incident energy, but also on the electric field strength. It is also proved that the transmission time and reflection time for two propagation directions satisfy reciprocal relation, resulting from the time reversal invariance in quantum mechanism.

Controllable negative and positive group delay in transmission through a single quantum well at finite magnetic fields

We investigate the controllable negative and positive group delay in transmission through a single quantum well at the finite longitudinal magnetic fields. It is shown that the magneto-coupling effect between the longitudinal motion component and the transverse Landau orbits plays an important role in the group delay. The group delay depends not only on the width of potential well and the incident energy, but also on the magnetic-field strengthen and the Landau quantum number. The results show that the group delay can be changed from positive to negative by the modulation of the magnetic field. These interesting phenomena may lead to the tunable quantum mechanical delay line.

Negative group delay for Dirac particles traveling through a potential well

The properties of group delay for Dirac particles traveling through a potential well are investigated. A necessary condition is put forward for the group delay to be negative. It is shown that this negative group delay is closely related to its anomalous dependence on the width of the potential well. In order to demonstrate the validity of stationary-phase approach, numerical simulations are made for a Gaussian-shaped temporal wave packet. A restriction to the potential-well's width is obtained that is necessary for the wave packet to remain distortionless in the traveling. Numerical comparison shows that the relativistic group delay is larger than its corresponding nonrelativistic one.