Resonant Zener Tunneling Research Articles

Chirped dual periodic structures for photonic Bloch oscillations and Zener tunneling.

Experimental evidence of photon Wannier-stark ladders (WSLs) and Zener tunneling (ZT) in one dimensional dual-periodical (DP) optical superlattices based on Porous Silicon (PSi), is presented. An introduction of linear gradient in physical thickness of the layers, composed of five stacks of two different periodic substructures, resulted in the appearance of four WSLs resonances and resonant Zener tunneling of nearest resonances of two consecutive WSLs. Theoretical analysis of time-resolved reflection spectra as a function of gradient reveals the presence of photonic Bloch oscillations (BOs) and an eventual tunneling at a specific value of linear gradient (20%), has been demonstrated through scattering maps. Measured reflection from different DP photonic structures confirm the presence of minibands, WSLs and ZT in the near infrared region.

Plasmonic Bloch oscillations and resonant Zener tunneling in subwavelength metal-dielectric-air waveguide superlattices

In this paper, we study the propagation properties of surface plasmon polaritons in plasmonic single-cavity superlattices and two-cavity superlattices which are composed of two kinds of alternately stacked subwavelength metal-dielectric-air waveguides with large dispersion. Theoretical predictions of plasmonic time-resolved Bloch oscillations existing in single-cavity superlattices and resonant Zener tunneling (ZT) occurring in two-cavity superlattices by the transfer matrix method (TMM) are well demonstrated by the numerical simulations on the propagation of SPPs pulse in the two kinds of superlattices by the finite-difference time-domain (FDTD) method. The two proposed superlattices can be conveniently fabricated by present nanotechnology, and the study may promote the realization of plasmonic BO and resonant ZT in nanoscale devices experimentally.

Zener tunneling in semiconductor superlattices

Characteristics of miniband tunneling and Wannier–Stark levels in semiconductorsuperlattices are studied as regards their dependence on the symmetry of the unit cells andthe type of miniband structure. We modify the k ⋅ p method into a k ⋅ v form and on this basis generalize the Zener formula for the inter-band tunneling inhomogeneous semiconductors to the case of inter-miniband tunneling in superlattices,account being taken of the inhomogeneity of the electron effective mass. The correspondingsum rule for the effective masses in such structures is obtained. We develop a unifiedmatrix approach for the calculation of the inter-miniband tunneling and Wannier–Starklevels in the case of an arbitrary number of minibands. We study the electric fielddependence of the probability of inter-miniband tunneling for an electron transferredthrough the Brillouin minizone only once. The peculiarities of the inter-minibandtransitions for the case where this transfer is repeated are also examined for various unitcells and miniband structures of the superlattice. In addition, we discuss mechanisms andspecific features of the resonant Zener tunneling and its manifestations in electrontransport.

Optical Bloch oscillation and resonant Zener tunneling in one-dimensional quasi-period structures containing single negative materials

We studied the optical Bloch oscillation and resonant Zener tunneling in macroscopic quasi-period structures of alternatively stratified single negative and dielectric slabs. By a decrease in the thicknesses of the dielectric slabs, the electronic potential of crystals subjected to external dc electric fields is mimicked and the optical Wannier–Stark ladder (WSL) is realized. Both scattering states and the time-resolved transmission of a short pulse are provided to show the existence of the optical analogue of electronic Bloch oscillation. At a critical gradient, the resonant photon Zener tunneling is demonstrated both from the amplitude and the time delay in the transmitted signal of a short pulse.

Momentum filter using resonant Zener tunneling

We consider the formation of a double barrier structure which includes both the valence and conduction bands in an $\mathrm{In}\mathrm{Sb}∕\mathrm{In}\mathrm{Al}\mathrm{Sb}$ quantum well system and demonstrate basic features of the transport process through this structure, which exhibits Zener tunneling. In particular, we employ an eight-band model and the Landauer-B\"uttiker formalism [Phys. Rev. B 31, 6207 (1985)] to investigate the transport process which under high confinement involves resonant energy levels due to the induced quasibound states in the valence bands. The mechanism of momentum filtering, taking advantage of resonant Zener tunneling, is shown to give improved performance at elevated temperatures compared with a unipolar double barrier resonant tunneling structure.

Vapor control of resonant Zener tunneling of light in a photonic crystal

AbstractWe show a vapor controlled one‐dimensional photonic crystal built with a silicon‐based dielectric mesoporous material, in which the refractive index can be continuously tuned by flowing organic vapors through the pores. Exposure of the crystal to vapors induces an inhomogeneous change in the refractive index through the depth and results in a tilted photonic band structure. We drive the photonic crystal to the optical Zener breakdown condition, introducing an enhanced transmission channel through the crystal. This phenomenon closely resembles the electronic Zener breakdown in a reverse‐biased p–n junction. The effect is reversible and opens new perspectives for physics in photonic crystals and novel device concepts based on sensing, switching and processing of light. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Acoustic Analogue of Electronic Bloch Oscillations and Resonant Zener Tunneling in Ultrasonic Superlattices

We demonstrate the existence of Bloch oscillations of acoustic fields in sound propagation through a superlattice of water cavities and layers of methyl methacrylate. To obtain the acoustic equivalent of a Wannier-Stark ladder, we employ a set of cavities with different thicknesses. Bloch oscillations are observed as time-resolved oscillations of transmission in a direct analogy to electronic Bloch oscillations in biased semiconductor superlattices. Moreover, for a particular gradient of cavity thicknesses, an overlap of two acoustic minibands occurs, which results in resonant Zener-like transmission enhancement.

Resonant Zener tunneling in two-dimensional periodic photonic lattices

We study Zener tunneling in two-dimensional photonic lattices and derive, for the case of hexagonal symmetry, the generalized Landau-Zener-Majorana model describing resonant interaction between high-symmetry points of the photonic spectral bands. We demonstrate that this effect can be employed for the generation of Floquet-Bloch modes and verify the model by direct numerical simulations of the tunneling effect.

Tuning of resonant Zener tunneling by vapor diffusion and condensation in porous optical superlattices

We study a vapor-controlled optical superlattice realized with a silicon-based dielectric mesoporous material. By flowing organic vapors through the nanometer-sized pores, the position dependent refractive index can be continuously tuned, resulting in a tilted photonic band structure. A careful design of pore size distribution, close to the critical radius of capillary condensation of vapor, makes the superlattice sensitive to the flow direction. We drive the optical superlattice to the resonant Zener tunneling condition, introducing an enhanced transmission channel through the photonic crystal. Our results show that vapor capillary condensation can be used to modify the properties of optical superlattices allowing, e.g., to realize fast gas sensing devices due to their advantage to respond to vapor flow fronts.

Nonresonant and resonant Zener tunneling

The Zener tunneling rate is derived by quantum-mechanical perturbation theory, using the Kane functions as base functions. This result is able to describe both nonresonant and resonant tunneling and is in line with recent experimental findings on Zener tunneling in superlattices. In contrast, the result published in the literature, which is the state of art up until now, does not adequately describe resonant Zener tunneling and is not an improvement over the semiclassical theory. The reason for that is a misconception about the initial condition.

Terahertz emission due to interminiband resonant Zener tunneling in wide-miniband GaAs/Al0.3Ga0.7As superlattices

We have investigated terahertz (THz) emission induced by high-field electron transport in biased wide-miniband GaAs/Al0.3Ga0.7As superlattices. With increasing bias electric fields, two distinct regimes are observed in the bias-field dependence of the emitted THz intensity. These two regimes are attributed to the intraminiband transport and interminiband Zener tunneling regimes, respectively. In the Zener tunneling regime, quasiperiodic structures are observed in the bias field dependence of the emitted THz intensity and are identified to be due to the resonant Zener tunneling between the Wannier–Stark ladders associated with the ground and excited minibands.

Inter-miniband resonant Zener tunneling in wide-miniband GaAs/Al 0.3Ga 0.7As superlattices investigated by THz emission spectroscopy

We have investigated the high-field transport in biased wide-miniband GaAs/Al 0.3Ga 0.7As superlattice (SL) diodes. Terahertz (THz) emission spectroscopy was performed on the emitted THz electromagnetic wave due to the electron motion in the SLs by using a bolometer as a wideband detector. With the increasing bias fields, two distinct regimes are observed in the bias-field dependence of the emitted THz intensity. These two regimes are attributed to the intra-miniband transport and inter-miniband Zener tunneling regimes, respectively. In the inter-miniband Zener tunneling regime, quasi-periodic structures are observed in the emitted THz intensity. The quasi-periodic peak structure is identified to be due to the resonant Zener tunneling between the Wannier–Stark ladders associated with the ground and the first-excited miniband. Resonant Zener tunneling up to the 9th-nearest-neighbor quantum wells was clearly resolved.

Lifetime of Wannier-Stark states in semiconductor superlattices under strong Zener tunneling to above-barrier bands

For high electric fields, the lifetime of Wannier-Stark ladder states in a periodic potential is reduced by the fundamental process of Zener tunneling. We report on the analysis of the coherence lifetime of such states in semiconductor superlattices by interband spectroscopy. The reduction of lifetime by strong coupling between bands can only in the first approximation be described by the well-known Zener theory. A recently developed theoretical model is applied to calculate directly the tunneling probability of Wannier-Stark states as a function of the electric field. The theoretical results compare well with experiment, reproducing the complex interplay of both nonresonant and resonant Zener tunneling to higher bands. By comparing experiment and theory for a superlattice with a symmetric and one with a nonsymmetric potential, we can draw conclusions on a very general basis about the sensitive dependence of Zener tunneling on the specific dispersion relation of the carriers.

Polarization revival of a Bloch-oscillating wave packet in conjunction with resonant Zener tunneling

We investigate the dynamics of a Bloch-oscillating wave packet in the presence of strong coupling to delocalized above barrier states (Zener tunneling), using time-resolved intraband polarization-sensitive measurements. At a threshold electric field, the resonance of localized and delocalized states causes a quantum beating which is observed as a revival in the intraband polarization. Our numerical simulation visualizes the spatial wave packet decomposition and reformation. The wave packet moves on a ps time scale over a distance of more than 100 nm and sequentially undergoes Bloch oscillations in the below- and above-barrier bands.

Direct resonant interband tunneling into exciton states in multiquantum well structures

Resonant Zener tunneling is investigated in a multiquantum-well p-i-n diode at cryogenic temperatures. Current-voltage characterization in presence of high magnetic fields demonstrates the dominant role of the electron–hole Coulomb interaction in driving this process. After a theoretical modelization in a variational scheme we conclude that tunneling electrons are directly injected into exciton states. We also suggest that similar transport experiments can be an alternative exciton spectroscopic technique with respect to the more conventional optical ones.

Resonant phenomena in compact and extended systems

We consider the dynamics of Josephson junctions in two formulations: one where the phase is defined on a compact interval [0,2\ensuremath{\pi}], and a second where it is defined on an extended interval (-\ensuremath{\infty},\ensuremath{\infty}). We find that in general the two approaches are not equivalent: they have different sets of allowable initial conditions, and similar initial conditions can produce different values for observables. However, they do have identical predictions for the appearance of resonances. These resonances can be understood in a framework of ``resonant Zener tunneling,'' which encompasses resonant tunneling in superlattices, tunneling between Wannier-Stark states in crystals, and Landau-Zener transitions in small metal rings. This framework also reveals a type of resonance in some quantum systems that are strongly driven (i.e., in the sudden limit), wherein the system has a large amplitude to transfer out of the diabatic state.

Resonant Zener tunneling of electrons between valence-band and conduction-band quantum wells

We report the observation of resonant tunneling effects at high applied fields in the reverse-bias current-voltage characteristic of multiple quantum well p-i-n diodes. The Al0.48In0.52As/Ga0.47In0.53As structure (grown by molecular beam epitaxy with 35 periods of 139 Å barriers and 139 Å wells) shows two steps in the dark current. These are associated with Zener tunneling of electrons across the band gap from the lowest subband in the valence-band quantum wells to the first and second subbands of adjacent conduction-band wells.