Scattering of a Single Plasmon by Three Non-equally Spaced Quantum Dots System Coupled to One-Dimensional Waveguide

Scattering properties of a single plasm on interacting with three non-equally spaced quantum dots coupled to one-dimensional surface plasmonic waveguide is investigated theoretically via the real-space approach. It is demonstrated that the transmission and reflection of a single plasmon can be switched on or off by controlling the detuning and changing the interparticle distances between the quantum dots. By controlling the transition frequencies and interparticle distances of QDs, one can construct a half-transmitting mirror with three QDs system. We also showed that controlling the transition frequencies and interparticle distances of QDs results in the complete transmission peak near the zero detuning

The effect of Magnetic Field on Spin Injection of DMS/FM Heterostructure

We discuss spin injection efficiency as a function of Fermi energy in DMS/FM heterostructures by spin injection efficiency equation and Landauer formula. The higher electric field, the stronger spin injection efficiency, and its velocity of increase gets lower and approaches to the equilibrium state. Additionally, the higher is interface conductivity, the weaker is spin injection efficiency, and the transmission as a function of Fermi energy for spin up and spin down is different from each other. This result causes the effect of the exchange interaction term in DMS. Finally, according to the investigation of spin injection efficiency as a function of the magnetic field in the same structure, the spin injection efficiency vibrates sensitively with the magnetic field. This result allows us to expect the possibility of spintronic devices with high sensitivity to magnetic field

Switching of a Single Photon by Two {\Lambda}-type Three-Level Quantum Dots Embedded in Cavities Coupling to One-Dimensional Waveguide

Switching of a single photon interacting with two {\Lambda}-type three-level quantum dots embedded in cavities coupled to one-dimensional waveguide is investigated theoretically via the real-space approach. We demonstrated that switching of a single photon can be achieved by tuning the classic driving field on or off, and by controlling the QD-cavity coupling strength, Rabi frequency and the cavity-waveguide coupling rate. The transmission properties of a single photon by such a nanosystem discussed here could find the applications in the design of next-generation quantum devices and quantum information.Comment: Accepted for publication to Plasmonics (Springer

Supersymmetric Matrix Quantum Mechanics with Non-Singlet Sector

We consider a supersymmetric matrix model which is related to the non-critical superstring theory. We find new non-singlet terms in the supersymmetric matrix quantum mechanics. The new non-singlet terms give rise to nontrivial interactions. These new non-singlet terms from fermions, can eliminate other non-singlet terms from generators of U(N) subalgebra and from time periodicity. The non-singlet terms from the generators violate the T-duality on the target space which is a circle. Therefore, we can retain the T-duality with a process of the elimination.Comment: 10 pages, two colum

New discrete method for investigating the response properties in finite electric field

In this paper we develop a new discrete method for calculating the dielectric tensor and Born effective charge tensor in finite electric field by using Berry's phase and the gauge invariance. We present a new method to overcome non-periodicity of the potential in finite electric field due to the gauge invariance, and construct the dielectric tensor and Born effective charge tensor that satisfy translational symmetry in finite electric field. In order to demonstrate the correctness of this method, we also perform calculations for the semiconductors AlAs and GaAs under the finite electric field to compare with the preceding method and the experiment.Comment: arXiv admin note: text overlap with arXiv:cond-mat/0612442 by other author

Entanglement of Two Quantum Dots with the Flip-Flop Interaction coupled to Plasmonic Waveguide

We investigate theoretically the entanglement of two quantum dots (QDs) coupled to metallic nanowaveguide in the presence of the flip-flop interaction with the analytical solutions of eigenvalue equations of the coupled system. High entanglement of two QDs could be achieved by adjusting the direct coupling strength of the QDs, the interaction of QDs with near-zero waveguide modes, interparticle distance of the QDs, total dissipation and detuning even when two QDs are resonant with the incident single plasmon. The discussed system with the flip-flop interaction provides us rich way to realize the quantum information processing such as quantum communication and quantum computation

Exciton-Plasmon Coupling Effects on the Nonlinear Optical Susceptibility of Hybrid Quantum Dot-Metallic Nanoparticle System

We have studied theoretically the exciton-plasmon coupling effects on the third-order optical nonlinearity of a coherently coupled hybrid system of a metal nanoparticle and a semiconductor quantum dot in the presence of a strong control field with a weak probe field

Influence of halide composition on the structural, electronic, and optical properties of mixed CH3_3NH3_3Pb(I1−x_{1-x}Brx_x)3_3 perovskites calculated using the virtual crystal approximation method

We investigate the structural, electronic and optical properties of mixed bromide-iodide lead perovskite solar cell CH$_3$NH$_3$Pb(I$_{1-x}$Br$_x$)$_3$ by means of the virtual crystal approximation (VCA) within density functional theory (DFT). Optimizing the atomic positions and lattice parameters increasing the bromide content $x$ from 0.0 to 1.0, we fit the calculated lattice parameter and energy band gap to the linear and quadratic function of Br content, respectively, which are in good agreement with the experiment, respecting the Vegard's law. With the calculated exciton binding energy and light absorption coefficient, we make sure that VCA gives consistent results with the experiment, and the mixed halide perovskites are suitable for generating the charge carriers by light absorption and conducting the carriers easily due to their strong photon absorption coefficient, low exciton bindign energy, and high carrier mobility at low Br contents. Furthermore analyzing the bonding lengths between Pb and X (I$_{1-x}$Br$_x$: virtual atom) as well as C and N, we stress that the stability of perovskite solar cell is definitely improved at $x$=0.2

Influence of Pulse width and Rabi frequency on the Population dynamics of three-level system in two-photon absorption process

We investigate the population dynamics of the three-level system in the two-photon absorption (TPA) process, mainly focusing the influence of pulse width and Rabi frequency on the population dynamics of the system. We observe the dependency of the population with the Rabi frequency and the pulse width. We also show that the arbitrary superposition state consisted in two states, upper state and lower state, is possible by controlling the pulse width and Rabi frequency. The results obtained can be used to the case of more complex multilevel system and they can be valuable for coherent quantum control in quantum information processing.Comment: arXiv admin note: text overlap with arXiv:quant-ph/0402155 by other authors without attributio

Control of the Optical Response of an Artificial Hybrid Nanosystem Due to the Plasmon-Exciton Plasmon Coupling Effect

The optical response of an artificial hybrid molecule system composed of two metallic nanoparticles (MNPs) and a semiconductor quantum dot (SQD) is investigated theoretically due to the plasmon-exciton-plasmon coupling effects on the absorption properties of the hybrid nanosystem, which depends on the interaction between the induced dipole moments in the SQD and the MNPs, respectively. We show that the strong coupling of exciton and localized surface plasmons in such a hybrid molecules leads to appealing, tunable optical properties by adjusting the symmetry of the hybrid molecule nanosystem with controllable interparticle distances. We also address here the influence of the size of the MNPs and dielectric constant of the background medium on the optical absorption of the MNPs and SQD, respectively, which results in the interparticle Foster resonance energy transfer (FRET). Our results will open an avenue to deal with the surface-enhanced spectroscopies and potential application of the quantum information