Electric-field control of bound states and optical spectrum in window-coupled quantum waveguides

Abstract

Properties of the bound states of two quantum waveguides coupled via the window of the width s in their common boundary are calculated under the assumption that the transverse electric field E E E is applied to the structure. It is shown that the increase of the electric intensity brings closer to each other fundamental propagation thresholds of the opening and the arms. As a result, the ground state, which in the absence of the field exists at any nonzero s, exhibits the energy E 0 decrease for the growing E and in the high-field regime E 0 stays practically the same regardless of the size of the connecting region. It is predicted that the critical window widths s crn , n = 1, 2, . . ., at which new excited localized orbitals emerge, strongly depend on the transverse voltage; in particular, the field leads to the increase in s crn , and, for quite strong electric intensities, the critical width unrestrictedly diverges. This remarkable feature of the electric-field-induced switching of the bound states can be checked, for example, by the change of the optical properties of the structure when the gate voltage is applied; namely, both the oscillator strength and absorption spectrum exhibit a conspicuous maximum on their E dependence and turn to zero when the electric intensity reaches its critical value. Comparative analysis of the two-dimensional (2D) and 3D geometries reveals their qualitative similarity and quantitative differences. a) Electronic address: oolendski@sharjah.ac.ae

Bound-state evolution of Dirichlet waveguide with Neumann window(s) in transverse electric fields

“…The existence of bound states, the discrete energy spectrum, and asymptotics for large radius values were given. While these structures on their own have rich properties, they exhibit exciting phenomena under the influence of external electric [23,29] and magnetic fields [21,30]. The existence of bound states in coupled waveguides under the influence of electric field was confirmed by variational analysis [31].…”

“…The existence of bound states in coupled waveguides under the influence of electric field was confirmed by variational analysis [31]. The influence of the electric field on the appearance of excited states in window coupled waveguides was studied numerically [29]. This was done by finding the critical lengths, the length of the window at which the excited state emerges into the continuum, as a function of the electric field.…”

Quantum computing with quantum-Hall edge state interferometry

“…Here, we review recent proposals for the realization of quantum gates with ESs in the Hall regime at integer FF and results showing the capability of controlling the occupation of ESs up to the level of single carriers [14]. Time-dependent simulations of single-carrier interferometers based on III-V materials indicate the viability of this flying qubit approach, constituting a substantial improvement with respect to earlier proposals based on ballistic electrons in coupled quantum wires [1,2,[15][16][17][18][19][20][21]. Specifically, two different proposals will be illustrated, operating at FF 1 and 2, with the qubit defined as either the ES occupancy or the Landau level (LL) of the electron, respectively.…”