Binding energy of excitons in an infinitely deep spherical quantum dot under intense THz laser field
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Binding energy of excitons in an infinitely deep spherical quantum dot under intense THz laser field A OUADGUI
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J DIOURI and J KHAMKHAMI
The Laboratory of System of Information and Telecommunication, Team of Optics and Photonics, Faculty of Sciences, Abdelmalek Essaadi University, Tétouan, Morocco ∗ Corresponding author. E-mail: [email protected] MS received 31 July 2019; revised 23 October 2019; accepted 24 November 2019 Abstract. We study the effects of intense THz laser field on the ground-state binding energy of heavy hole excitons confined in GaAs spherical quantum dots. The calculation is performed using the variational method in the framework of the single band effective mass theory. Our results show that (i) the laser electric field lowers the binding energy for all quantum dot radii, making the exciton clustered near the centre of the dot, (ii) the binding energy is mainly due to the dressed potential making the kinetic part insensitive to the field and (iii) the behaviour of the exciton, under the approximations used, can be modelled by a unique set of plots, depending on the material only via its excitonic units. Keywords. Exciton; quantum dot; laser field; dressed potential; binding energy; variational method. PACS Nos 73.21.La; 73.63.Kv
1. Introduction Over the last decades, confined excitons in quantum dots have been largely investigated experimentally and theoretically for a wide variety of II–VI and III–V semiconductor compounds because of their original properties that allow many interesting applications, namely, producing artificial atoms and molecules, single-electron transistors, quantum dot lasers [1] and quantum-bit [2]. The base of these applications is the large dependence of the exciton binding energy on different and adjustable parameters: the radius of the dot, the effective masses of the carriers, the height and the shape of the confining potential caused by the matrix material in which the exciton is embedded [3–5]. Various external actions, such as magnetic field [6], electric field [7,8] and hydrostatic pressure [9] have already been considered. Recently, some researchers have shown interest in intense terahertz (THz) laser effects on excitons in bulk semiconductor [10,11] and in GaInNAs/GaAs quantum wells [12]. In the former case, calculation of near absorption and transient concludes that the excitons are stabilised against the field ionisation [11]. This counterintuitive effect was confirmed by Lima [10]. By computing the binding energy of excitons in bulk GaAs semiconductor, it is found that this decreases 0123456789().: V,-vol
with increasing field intensity and leads to a quarter of the exciton Rydberg energy [10]. In GaInNAs/GaAs quantum wells, Yesilgul [12] found similar trends for all the widths of the well and showed that the intense THz laser field creates an additional geometric confinement on the ground state of the exciton. This work is an extension of these studies, and the purpose of this work is to examine the case of quantum dot exc
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