arXiv subjects

Nguyen Dung Chinh

Publications and source records attributed to Nguyen Dung Chinh.

4 recordsLinked to original sources

arXiv2025

Tuning the lasing threshold of quantum well exciton-polaritons under a magnetic field in Faraday geometry: a theoretical study

Polariton lasing is a promising phenomenon with potential applications in next-generation lasers that operate without the need for population inversion. Applying a perpendicular magnetic field to a quantum well (QW) significantly alters the properties of exciton-polaritons. In this theoretical study, we investigate how the lasing threshold of QW exciton-polaritons depends on the magnetic field. By modifying the exciton's effective mass and Rabi splitting, the magnetic field induces notable changes in the relaxation kinetics, which directly affect the lasing threshold. For low-energy pumping, an increase in the magnetic field delays the lasing threshold, while for high-energy pumping, the threshold is reached at much lower pump intensities. Furthermore, increasing both the pump energy and the magnetic field enhances relaxation efficiency, leading to a substantially larger number of condensed polaritons. Our result gives insights into the modulation of exciton-polariton condensation through magnetic fields, with potential implications for the design of low-threshold polariton lasers.

cond-mat.mes-hall↗

arXiv2025

Significant Enhancement of Carrier Mobility in Finite vs. Infinite Square Quantum Wells: A Comparative Study of GaAs/In$_x$Ga$_{1-x}$As/GaAs Heterostructures

The geometry of quantum wells (QWs) critically influences carrier mobility, yet systematic comparisons between finite and infinite square QWs remain scarce. We present a comprehensive study of GaAs/In$_x$Ga$_{1-x}$As/GaAs heterostructures using a variational-subband-wave-function model, analyzing key scattering mechanisms: remote impurities (RI), alloy disorder (AD), surface roughness (SR), acoustic (ac) and piezoelectric (PE) phonons, and longitudinal optical (LO) phonons. The mobility ratio $R=μ_{fin}/μ_{inf}$ reveals distinct trends: $R_{RI}$ and $R_{LO}<$ 1 (long-range Coulomb/inelastic scattering), while $R_{AD}$, $R_{ac}$, $R_{PE}$, $R_{SR}>$ 1 (static potentials). Finite QWs achieve higher mobility at low temperatures (77 K), narrow widths ($<$ 100 Å), and low densities, enhanced by high indium content. Conversely, infinite QWs outperform at 300 K due to dominant LO scattering. These findings provide actionable guidelines for optimizing QW-based devices such as HEMTs and lasers across operational regimes.

cond-mat.mes-hall↗

arXiv2024

Impact of cut-off frequency effect on resonance energy transfer and Casimir-Polder interaction

Using the Green's function approach, we investigate the resonance energy transfer (RET) rate between two parallel, identical two-level atoms in the presence of three types of cylindrical system: a distributed Bragg reflector (DBR), a perfectly reflecting wall (PRW), and a two-layer silicon fiber. Our analysis, incorporating the cut-off frequency condition, reveals significant suppression of the RET rate for atoms positioned along the axis of the cylinder with the PRW. In contrast, for atoms located within the DBR, the RET rate is enhanced in the far zone. Additionally, we find that for atoms oriented radially are placed inside or near the surface of the silicon fiber, the RET rate is entirely inhibited. We also investigate the Casimir-Polder (CP) interaction between a cut-off-frequency DBR and an excited atom, discovering a fully attractive potential towards the surface for the atom within the waveguide.

physics.optics↗

arXiv2024

Effect of magnetic field on the Bose-Einstein condensation of quantum well exciton-polaritons

We theoretically investigate the nonlinear effects of a magnetic field on the relaxation process of exciton-polaritons toward Bose-Einstein condensation in GaAs quantum wells. Our study reveals that the modification of the exciton's effective mass, Rabi splitting, and dispersion significantly alters the relaxation rate of polaritons as they approach condensation. By employing a quasi-stationary pump, we clarify the dynamics of the total and condensed polariton populations in response to varying magnetic field strengths. Notably, we demonstrate that under low-energy pumping conditions, the presence of a magnetic field significantly suppresses condensation. This suppression is attributed to the decreased scattering rate between energy levels, which is a consequence of the reduced steepness in the high-energy dispersion. Conversely, increasing both the pump energy and the magnetic field can enhance relaxation efficiency, leading to a substantially larger number of condensed polaritons.

quant-ph↗