Quasienergy spectrum and tunneling current in ac-driven triple quantum dot shuttles

TL;DR

This paper investigates the quasienergy spectrum and tunneling behavior in a triple quantum dot system driven by an ac field, revealing conditions for coherent destruction of tunneling and symmetry properties of Floquet states.

Contribution

It extends Floquet theory analysis to a triple quantum dot system with mechanical oscillation, deriving analytical conditions for tunneling suppression and symmetry characteristics.

Findings

Identifies conditions for coherent destruction of tunneling (CDT).

Derives analytical expressions for quasienergies under strong driving.

Shows quasienergy spectrum crossings linked to symmetry properties.

Abstract

The dynamics of electrons in ac driven double quantum dots have been extensively analyzed by means of Floquet theory. In these systems, coherent destruction of tunneling has been shown to occur for certain ac field parameters. In the present work we analyze, by means of Floquet theory, the electron dynamics of a triple quantum dot in series attached to electric contacts, where the central dot position oscillates. In particular, we analyze the quasienergy spectrum of this ac driven nanoelectromechanical system, as a function of the intensity and frequency of the ac field and of external dc voltages. For strong driving fields, we derive, by means of perturbation theory, analytical expressions for the quasienergies of the driven oscillator system. From this analysis we discuss the conditions for coherent destruction of tunneling (CDT) to occur as a function of detuning and field parameters. For zero detuning, and from the invariance of the Floquet Hamiltonian under a generalized parity transformation, we find analytical expressions describing the symmetry properties of the Fourier components of the Floquet states under such transformation. By using these expressions, we show that in the vicinity of the CDT condition, the quasienergy spectrum exhibits exact crossings which can be characterized by the parity properties of the corresponding eigenvectors.