In this paper, we examine the three-level optical Stark effect of excitons in InGaAs/InAlAs quantum dots using renormalized wavefunction formulation. The system was assumed to be irradiated by two lasers in which a strong laser dynamically couples electron-quantized levels, while a weaker laser probes interband absorption. Our results show that, in the presence of the resonant strong laser, two new absorption peaks of excitons appear in the absorption spectrum as a clear indication of the effect. In addition, we propose that the formation of the effect in lowdimensional structures could have connection to the splitting of electron levels. Furthermore, we seek to explain the essential dependence of the amplitude and position of two peaks on pump field detuning.

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This paper presents a theoretical investigation of quantum beats of excitons in GaAs/AlGaAs circular cylindrical quantum wires. A three-level model of excitons, including a ground state and two excited states, has been applied to derive the renormalized wavefunctions and the time-dependent absorption intensity of excitons when the system is irradiated by a strong pump laser resonating with the distance between the two excited-levels. Our results show that a periodic oscillation form of the absorption intensity, obvious evidence of the quantum beat behavior, has appeared. Furthermore, the mechanism of the generation, as well as the effects of the wire radius and the pump laser detuning on the frequency (period) and amplitude of quantum beats, have been explained in detail. These results suggest potential applications in the fabrication of some quantum computation devices.

In this paper, we study the exciton absorption spectra in InGaAs prolate ellipsoidal quantum dots when a strong pump laser resonant with electron quantized levels is active. Our obtained results by renormalized wavefunction theory show that, under suitable conditions, the initial exciton absorption peak is split into two new peaks as the evidence of the existence of the three-level optical Stark effect of excitons. We have suggested an explanation of the origin of the effect as well as investigating the effect of pump field energy, size, and geometric shape of the quantum dots on effect characteristics. The comparison with the results obtained in the spherical quantum dots implies the important role of geometric shape of the quantum structures when we examine this effect.

The crystal structure, electronic structure, and diffusion mechanism of Na ions in the cathode material Na 2 Mn 3 (SO 4 ) 4 are investigated based on the Heyd−Scuseria−Ernzerhof hybrid density functional method. The simultaneous motion model of polaron−sodium vacancy complexes was used to reveal the diffusion mechanism of Na ions in this material. Polaron formation at the Mn third-nearest neighbor to the Na vacancy was found. Two crossing and two parallel elementary diffusion processes of the polaronNa vacancy complex were explored. The most preferable elementary diffusion process has an activation energy of 852 meV, which generates a zigzag-like pathway of Na-ion diffusion along the [001] direction in the whole material. Possessing a voltage of 4.4 V and an activation energy of 852 meV, Na 2 Mn 3 (SO 4 ) 4 is expected to be a good cathode material for rechargeable sodium ions.