Electric-Field Control of Bound States and Optical Spectrum in Window-Coupled Quantum Waveguides

TL;DR

This paper investigates how an applied transverse electric field influences bound states and optical properties in window-coupled quantum waveguides, revealing electric-field-induced state switching and optical spectrum modifications.

Contribution

It provides a detailed analysis of electric-field effects on bound states, including critical widths and optical responses, in coupled quantum waveguides, a novel insight into quantum control mechanisms.

Findings

Electric field decreases ground state energy with increasing intensity.

Critical window widths for excited states increase with electric field and can diverge.

Optical properties like oscillator strength and absorption spectrum show maxima at certain electric fields.

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 $\pmb{\mathscr{E}}$ 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 $\mathscr{E}$ 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 $s_{cr_n}$, $n=1,2,\ldots$, at which new excited localized orbitals emerge, strongly depend on the transverse voltage; in particular, the field leads to the increase of $s_{cr_n}$, 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 $\mathscr{E}$ 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.