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THz Radiation Using Gases/Plasmas
Published in Hitendra K. Malik, Laser-Matter Interaction for Radiation and Energy, 2021
Ionization involves an electron escape from the atom (or molecule) via crossing the potential barrier. Classically, an electron must have a higher amount of energy compared with that of the potential barrier and only then it is allowed to leave the atom (or molecule). But with the application of an external field, the height of the potential barrier can be suppressed, and the electron can easily tunnel through the potential instead of going all over the way due to its wave nature. This distortion of potential barrier, due to intense electric field, permits the electron to escape from the atom. This quantum mechanical phenomenon where ionization happens due to quantum tunneling, which is forbidden by the classical laws, is known as tunnel ionization. Tunnel ionization allows the particle to escape from the distorted Coulomb potential barrier with non-zero probability. The probability of an electron's tunneling through the barrier with the width of the potential barrier drops off exponentially. Therefore, an electron with higher energy encounters a thinner potential barrier, which further increases the tunneling probability.
Theoretical study of electron tunneling time through a single/double barrier(s), and the effect of wave packet spread
Published in Jong-Chun Woo, Yoon Soo Park, Compound Semiconductors 1995, 2020
Figure 3 shows various simulated times, theoretical time, and the classical time. The simulation is performed for the first resonant level tunneling in a symmetric double-barrier structure with barrier height of 300meV, barrier width of 3nm, and well width of 5nm. Excitation time is the time elapse between the moment when the peak of the incident wave packet reaches the front potential barrier and the moment when trapped electron probability becomes maximum. Decay time is the time elapse between the moment when the trapped electron probability becomes maximum and the momentum when it is reduced to half of its maximum. Tunneling time is the time elapse between the moment when the peak of the incident wave packet reaches the front potential barrier and the moment when the peak of the transmitted wave packet leaves the right barrier. Classical time is the pass time of an electron with the same energy across the same region in the absence of the potential barriers. Figure 4 is for the case of 5nm barrier thickness with other conditions equal to those for Figure 3.
Elements of Quantum Electronics
Published in Michael Olorunfunmi Kolawole, Electronics, 2020
Another fabrication technique to building these qubits is scanning tunneling microscope (STM). STM is an instrument for imaging surfaces at the atomic level, based on the concept of quantum tunneling. Tunneling is a functioning concept that describes the behavior of a quantum object (with a very small mass, such as the electron) when it hits a barrier. If the barrier is thick, the object bounces off. However, if the barrier is thin enough, the object may sometimes get through. The thinner the barrier, the more likely the object passes. A metal is made up of quantum atoms and electrons. If we approach a very thin tip electrically powered, it may tear the electrons from the metal by tunnel effect. By measuring the electric current passing through the tip, we can reconstruct where the atoms are. This is the principle of STM. Using STM concept, the University of New South Wales, Sydney Australia, proved for the first time and fabricated a working quantum transistor consisting of a single atom placed precisely in a silicon crystal [37]. Figure 9.31 illustrates the operation of a single atom transistor. A voltage is applied across the phosphorus electrodes, which induces a current that forms electrical leads for a single phosphorus atom positioned precisely in the center of the silicon crystal.
Energy Analysis of Metal QCA Circuits Behavior Based on Particle-Wave Duality
Published in IETE Journal of Research, 2022
Masoumeh Shirichian, Reza Akbari-Hasanjani, Reza Sabbaghi-Nadooshan
A metal QCA cell consists of four metal islands sitting in four corners of a square cell, inside which two free electrons are confined (Figure 1(a) and (b)). These electrons are allowed to tunnel between quantum dots. Quantum dots are shown in Figure 1 means infinite potential wells one of which is shown as one-dimensional in Figure 2. There is the possibility of tunneling by electrons between potential wells. But, tunneling between adjacent cells is impermissible. Coulomb's repulsion law states that electrons can only occupy antipodal sites in the cell; hence, polarization states P = −1 and P = +1 can be made by electrons. Quantum measurement can determine whether the quantum number of each electron is positive or negative [25]. In QCA cells, reverse polarization or rotation can be detected through the electron position, which can change based on external electrostatic energy. In this article, particle-wave duality formalism is used that when the electrons are stationary, they have fixed positions and act like particles, and the laws of classical physics can be used to describe their behavior. But when they are moving, for tunneling between the quantum dots to achieve a specific polarization, they act as waves and should be treated by the laws of quantum mechanics, which was corrected on page 3 and shown in green.
The electric and magnetic field effects on the optical absorption in double QWs with squared, U-shaped and V-shaped confinement potentials
Published in Philosophical Magazine, 2023
Redouane En-nadir, Haddou El-ghazi, Hassan Abboudi, Ibrahim Maouhoubi, Anouar Jorio, Izeddine Zorkani, Mohammed El-Ganaoui
The linear and nonlinear optical properties of these systems have been extensively studied [15–19]. There has been a lot of previous work on the evaluation of the optical and electronic properties of electrons in quantum wells. Particularly, the investigation of multiple quantum wells and full 2D wells to understand optical and electronic properties in Ga-based systems and also taken into account the incorporation of doping effects on electrostatic potential to give a more realistic treatment of these systems [20–22]. Moreover, the optical absorption coefficients in these systems can be affected by many external and internal parameters such as electric and magnetic field; structure geometry, impurities (donors and/or acceptors), hydrostatic pressure, temperature, compositions, etc. One of these nanostructures is the double quantum well (DQW) structure. The latter offers the possibility of tunneling the particle through the barrier, which gives rise to new quantum phenomena that could be useful for the innovation of new technologies [23]. Many electronic and optoelectronic applications require electron tunneling through barriers such as laser diodes, photodetectors and LEDs. These devices are mainly based on quantum well (QW) resonant tunneling diodes (RTDs). RTDs are nano-devices that have negative differential resistance (NDR) characteristics. They allow electrons to pass through various resonance states at specific energy levels. Therefore, RTDs are used in digital and analogue circuits to reduce power dissipation. The efficiency of modelling semi-polar, polar and non-polar InGaN has been investigated in a previously [24].
Bound state solutions, Fisher information measures, expectation values, and transmission coefficient of the Varshni potential
Published in Molecular Physics, 2021
E. Omugbe, O. E. Osafile, I. B. Okon, E. A. Enaibe, M. C. Onyeaju
On the other hand, the expectation values or mean values of quantum mechanical observables play an important role in quantum mechanics in that it can be applied to determine the most probable position of an electron confined in a nucleus over a range of radial distance [27]. Also, the mean values may be used to determine the variance and uncertainty of an observable. Furthermore, the tunnelling properties of a quantum particle may be exploited in electronic devices. It may also help in explaining Gamow’s alpha decay theory or the escape of alpha particles from the nuclei of heavy elements and the skin depth effect for a classical electromagnetic wave reflecting from a conducting surface [27,28].