The duality of a single particle with an n-dimensional internal degree of freedom

The wave-particle duality of a single particle with an n-dimensional internal degree of freedom is re-examined theo- retically in a Mach-Zehnder interferometer. The famous duality relation D2 ＋ V2 〈 1 is always valid in this situation, where D is the distinguishability and V is the visibility. However, the sum of the particle information and the wave information, D2 V2, can be smaller than one for the input of a pure state if this initial pure state includes the internal degree of freedom of the particle, while the quantity D2~ V2 is always equal to one when the internal degree of freedom of the particle is excluded.     

On the tunneling through a time dependent barrier

Tunneling of a nucleon through a monotonically shrinking rectangular barrier is solved exactly. Some consequences for the nucleon-transfer in the approach phase of two colliding heavy nuclei are discussed.     

Nonlinear tunneling through a strong rectangular barrier

Nonlinear tunneling is investigated by analytically solving the one-dimensional Gross–Pitaevskii equation(GPE)with a strong rectangular potential barrier. With the help of analytical solutions of the GPE, which can be reduced to the solution of the linear case, we find that only the supersonic solution in the downstream has a linear counterpart. A critical nonlinearity is explored as an up limit, above which no nonlinear tunneling solution exists. Furthermore, the density solution of the critical nonlinearity as a function of the position has a step-like structure.     

Complete tunneling of light through a barrier with anisotropic metamaterial

We construct a barrier with anisotropic metamaterial to explore the complete tunneling conditions of light through it. And then we take a semiconductor metamaterial as an example to discuss the dispersive properties of the barrier and show a possible application as a flat-top filter.     

Dynamical tunneling of bound systems through a potential barrier: Complex way to the top

A semiclassical method of complex trajectories for the calculation of the tunneling exponent n systems with many degrees of freedom is further developed. It is supplemented with an easily implemented technique that enables one to single out the physically relevant trajectory from the whole set of complex classical trajectories. The method is applied to semiclassical transitions of a bound system through a potential barrier. We find that the properties of physically relevant complex trajectories are qualitatively different in the cases of potential tunneling at low energy and dynamical tunneling at energies exceeding the barrier height. Namely, in the case of high energies, the physically relevant complex trajectories describe tunneling via creation of a state close to the top of the barrier. The method is checked against exact solutions of the Schrödinger equation in a quantum-mechanical system of two degrees of freedom.     

Particle tunneling and scattering in a three-dimensional potential with a barrier

The particle tunneling through a 3-D rectangular potential barrier has been studied. The simplest model for multiple internal reflections has been assumed. The explicit expression for all the transmission and reflection probability amplitudes have been derived, as well as the tunneling and reflection phase times.      

Lateral tunneling through the controlled barrier between edge channels in a two-dimensional electron system

A study is made of the lateral tunneling between edge channels at the depletion-induced edges of a gated two-dimensional electron system, through a gate-voltage-controlled barrier arising when the donor layer of the heterostructure is partly removed along a fine strip by means of an atomic force microscope. For a sufficiently high barrier the typical current-voltage characteristic is found to be strongly asymmetric, having, in addition to the positive tunneling branch, a negative branch that corresponds to the current overflowing the barrier. It is established that the barrier height depends linearly on both the gate voltage and the magnetic field, and the data are described in terms of electron tunneling between the outermost edge channels. Pis’ma Zh. éksp. Teor. Fiz. 69, No. 8, 561–566 (25 April 1999) Published in English in the original Russian journal. Edited by Steve Torstveit.     

Room-temperature tunnel magnetoresistance and spin-polarized tunneling through an organic semiconductor barrier

Electron spin-polarized tunneling is observed through an ultrathin layer of the molecular organic semiconductor tris(8-hydroxyquinolinato)aluminum (Alq3). Significant tunnel magnetoresistance (TMR) was measured in a Co/Al2O3/Alq3/NiFe magnetic tunnel junction at room temperature, which increased when cooled to low temperatures. Tunneling characteristics, such as the current-voltage behavior and temperature and bias dependence of the TMR, show the good quality of the organic tunnel barrier. Spin polarization (P) of the tunnel current through the Alq3 layer, directly measured using superconducting Al as the spin detector, shows that minimizing formation of an interfacial dipole layer between the metal electrode and organic barrier significantly improves spin transport.     

Tunneling through a disordered potential barrier

Tunnelling through a weakly disordered potential barrier is studied analytically. A perturbative approach is developed to calculate all statistical moments of the tunnelling transmission coefficient, and its probability distribution function. It is shown that on average disorder enhances the tunnelling conductance, resistance, and the coherent component of the transmitted field.On leave from the Institute of Low-Temperature Physics and Engineering, Kharkov 310164, Ukraine.     

Quasiparticle tunneling through a barrier in the fractional quantum hall regime

Tunneling of fractionally charged quasiparticles (QPs) through a barrier is considered in the context of a multiply connected geometry. In this geometry global constraints do not prohibit such a tunneling process. The tunneling amplitude is evaluated and the crossover from mesoscopic QP-dominated to electron-dominated tunneling as the system's size is increased is found. The presence of disorder enhances both electron and QP-tunneling rates.     

Electron tunneling through thin barrier with smooth potential at GaAs/AlAs(001) heterointerfaces

The influence of actual microscopic potential on the characteristics of resonant electron tunneling from the Γ valley in GaAs through the AlAs barrier with thickness of one lattice constant has been investigated by the methods of pseudopotential and scattering matrix factorized by the irreducible representations of the symmetry group of the heterostructure. The transition regions between the potentials of components and the barrier region are treated as the components of the Ga₂Al₂As₄ superlattice spacing to provide the continuity of the crystal potential at the boundaries of the matching of wave functions. It is demonstrated that, compared to the results obtained in the abrupt-interface model, the inclusion of the actual potential in the calculation leads to changes in the number and location of the Fano resonances, an enhancement in the localization of electron density within the barrier, and a drastic increase in the tunneling time.     

Photon tunneling in a frustrated total internal reflection structure with a lossy indefinite metamaterial barrier

We study the phenomenon of photon tunneling through a frustrated total internal reflection structure with a dispersive lossy indefinite metamaterial barrier. The tunneling coefficient, lateral shift, and tunneling time for different incident light waves through the barrier are obtained by employing the stationary-phase approximation. The properties of tunneling time and lateral shift are discussed for different metamaterial parameters. It is shown that negative lateral shift and tunneling time can appear in the cutoff and always cutoff metamaterials. The lateral shift can be enhanced by adjusting the light frequency, the barrier thickness, and the permittivity or permeability of the indefinite metamaterial. In addition, it is found that the lateral shift can be resonantly amplified due to the weak loss of the indefinite metamaterial slab. The Hartman effects of the lateral shift and tunneling time are also demonstrated. PACS 42.50.Ct; 42.25.Bs; 73.43.Jn; 73.40.Gk; 42.70.Qs     

Electron tunneling through a barrier that depends linearly on time

We discuss the creation of a negative molecular ion via the decay of a self-captured electron state — the fluctuon — in a nonideal dipole-molecule gas. The creation probability of the negative ion is evaluated in the classical approximation using Green's function methods. We assume that the potential barrier through which the electron tunnels from the potential well of the fluctuon to that of the molecule depends linearly on time.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 84–88, September, 1987.     

Resonance bands in a two degree of freedom Hamiltonian system

In perturbations of integrable two degree of freedom Hamiltonian systems, the invariant (KAM) tori are typically separated by zones of instability or resonance bands inhabited by elliptic and hyperbolic periodic orbits and homoclinic orbits. We indicate how the Melnikov method or the method of averaging can asymptotically predict the widths of these bands in specific cases and we compare these predictions with numerical computations for a pair of linearly coupled simple pendula. We conclude that, even for low order resonances, the first order asymptotic results are generally useful only for very small coupling (ε10^-4).