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Effects of Shannon entropy and electric field on polaron in RbCl triangular quantum dot

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Chinese Physics B 2016年第4期25卷 432-435页

作者： M Tiotsop A J Fotue S C Kenfack N Issofa H Fotsin L C Fai mesoscopic and multilayers structures laboratory Department of Physics Faculty of Science University of Dschang laboratory of Electronics and Signal Processing Department of Physics Faculty of Science University of Dschang

In this paper, the time evolution of the quantum mechanical state of a polaron is examined using the Pekar type variational method on the condition of the electric-LO-phonon strong-coupling and polar angle in RbC1 triangular quantum dot. We obtain the eigenenergies, and the eigenfunctions of the ground state, and the first excited state respectively. This system in a quantum dot can be treated as a two-level quantum system qubit and the numerical calculations are performed. The effects of Shannon entropy and electric field on the polaron in the RbC1 triangular quantum dot are also studied.

关键词： Shannon entropy polaron electric field triangular quantum dot

Thermodynamic Properties and Decoherence of a Central Electron Spin of Atom Coupled to an Anti-Ferromagnetic Spin Bath

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Journal of Quantum Information Science 2013年第1期3卷 10-15页

作者： Martin Tchoffo Georges Collince Fouokeng Lukong Cornelius Fai Mathurin Esouague Ateuafack mesoscopic and multilayer structures laboratory Department of Physics Faculty of Science University of Dschang Dschang Cameroon

The decoherence of a central electron spin of an atom coupled to an anti-ferromagnetic spin bath in the presence of a time varying B-Field (VBF) is investigated applying the Holstein-Primak off and Bloch transformations approaches. The Boltzmann entropy and the specific heat capacity at a given temperature are obtained and show the correlation of the coupling of the spin bath and the electron spin of the central atom. At low frequencies the coherence of the coupled system is dominated by the magnetic field intensity. At low VBF intensity, there is decrease in entropy and heat capacity at increase external magnetic field that show the decoherence suppression of the central electron spin atom. The crossing observed in the specific heat capacity corresponds to the critical field point Bc of the system which represents the point of transition from the anti-ferromagnetic system to the ferromagnetic one.

关键词： Entropy Specific Heat Capacity Varying B-Field Decoherence

Energy levels of magneto-optical polaron in spherical quantum dot—Part 1:Strong coupling

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Journal of Semiconductors 2015年第9期36卷 1-8页

作者： A.J.Fotue S.C.Kenfack N.Issofa M.Tiotsop H.Fotsin E.Mainimo L.C.Fai mesoscopic and multilayers structures laboratory Department of PhysicsFaculty of ScienceUniversity of Dschang laboratory of Electronics and Signal Processing Department of PhysicsFaculty of ScienceUniversity of Dschang

We investigate the influence of a magnetic field on the ground state energy of a polaron in a spherical semiconductor quantum dot （QD） using the modified LLP method. The ground state energy is split into sub-energy levels and there is a degeneracy of energy levels. It is also observed that the degenerate energy increase with the electron-phonon coupling constant and decrease with the magnetic field. The numerical results show that, under the influence of magnetic field and the interaction with the total momentum along the z-direction, the split energy increases and decreases with the longitudinal and the transverse confinement length, respectively.

关键词： magnetic field total momentum modified LLP polaron energy quantum dot

Surface plasmon polariton and mode transformation in a nanoscale lossy metallic cylindrical cable

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Chinese Physics B 2008年第10期17卷 3880-3893页

作者：杨鹏飞古英龚旗煌 State Key laboratory for mesoscopic Physics Department of Physics Peking University

A theoretical investigation on the surface plasmon polariton in a gold cylindrical nanocable is presented. By solving a complete set of Maxwell＇s equations in the nanocable （with a 50 nm radius gold nanocore, 10-300 nm silica layer, and 30-200nm gold nanocladding）, the dispersion relations on the optical frequency and on the silica thickness are discussed. When the silica thickness varies from 50 to 250 nm, at a fixed waveleltgth, the strong coupling between the gold nanocore and the nanocladding leads to a symmetric-like surface mode and an antisymmetric-like surface mode in the nanocable. The transformation between the surface mode and the waveguide mode in this structure is also investigated. The results will be helpful for understanding the surface waves in the subwavelength structures.

关键词： nanocable surface plasmons mode transformation

Electro-magnetic weak coupling optical polaron and temperature effect in quantum dot

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Journal of Semiconductors 2015年第10期36卷 9-15页

作者： M.Tiotsop A.J.Fotue S.C.Kenfack N.Issofa A.V.Wirngo M.P.Tabue Djemmo H.Fotsin L.C.Fai mesoscopic and multilayers structures laboratory Department of PhysicsFaculty of ScienceUniversity of Dschang laboratory of Mechanics and Modeling of Physical Systems Faculty of ScienceUniversity of Dschang laboratory of Electronics and Signal Processing Department of PhysicsFaculty of ScienceUniversity of Dschang

We investigate the influence of the electric field and magnetic fields on the ground state energy of a polaron in a spherical semiconductor quantum dot （QD） using the modified Lee Low Pines （LLP） method. The numerical results show the increase of the ground state energy with the increase of the electric field and the electron- phonon coupling constant, and the decrease with the magnetic field and the longitudinal confinement length. It is also seen that the temperature is an increasing function of the cyclotron frequency and the coupling constant whereas it decreases with the electric field strength. The modulation of the electric field, the magnetic field and the confinement length leads to the control of decoherence in the system.

关键词： electric field magnetic field modified LLP polaron energy quantum dot temperature

Electric and magnetic optical polaron in quantum dot—Part 1: strong coupling

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Journal of Semiconductors 2015年第7期36卷 1-6页

作者： A.J.Fotue N.Issofa M.Tiotsop S.C.Kenfack M.P.Tabue Djemmo H.Fotsin and L.C.Fai mesoscopic and multilayers structures laboratory Department of PhysicsFaculty of ScienceUniversity of Dschang laboratory of Mechanics and Modeling of Physical Systems Faculty of ScienceUniversity of Dschang laboratory of Electronics and Signal Processing Department of PhysicsFaculty of ScienceUniversity of Dschang

We investigated the influence of electric field and magnetic field on the ground state energy ofpolaron in spherical semiconductor quantum dot （QD） using a modified Lee Low Pines （LLP） method. The numerical results show the increase of the ground state energy with the increase of the electric field and the decreasing with the magnetic field. The modulation of the electric field, magnetic field and the confinement lengths lead to the control of the decoherence of the system.

关键词： electric field magnetic field modified LLP polaron energy quantum dot

Tapered dielectric structure in metal as a wavelength-selective surface plasmon polariton focuser

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Chinese Physics B 2009年第11期18卷 4865-4869页

作者：张洋赵清廖志敏俞大鹏 State Key laboratory for mesoscopic Physics and Electron Microscopy LaboratorySchool of PhysicsPeking University

Symmetric tapered dielectric structures in metal have demonstrated applications such as the nanofocusing of surface plasmon polaritons, as well as the waveguiding of V-channel polaritons. Yet the fabrication of smooth-surfaced tapered structure remains an obstacle to most researchers. We have successfully developed a handy method to fabricate metal-sandwiched tapered nanostructures simply with electron beam lithography. Though these structures are slightly different from conventional symmetric V-shaped structures, systematic simulations show that similar functionality of surface plasmon polariton nanofocusing can still be achieved. When parameters are properly selected, wavelength- selective nanofocusing of surface plasmon polaritons can be obtained.

关键词： tapered structure surface plasmon focusing finite-difference time-domain

Linear and Nonlinear Intersubband Optical Absorptions and Refractive Index Changes in InGaN Strained Single Quantum Wells： Strong Built-in Electric Field Effects

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Chinese Physics Letters 2007年第8期24卷 2376-2379页

作者：池月萌史俊杰 State Key laboratory for mesoscopic Physics and School of Physics Peking University Beijing 100871

Considering the strong built-in electric field （BEF） effects due to the spontaneous and piezoelectric polarizations, the intersubband optical absorptions and refractive index changes for an InxGa1-xN/AlyGa1-yN strained single quantum well are studied theoretically within the framework of the density matrix method and effective-mass approximation. The linear, third-order nonlinear and total absorption coefficients and refractive index changes are calculated as a function of the incident optical intensity and photon energy. Our results show that both the incident optical intensity and the strong BEF have great influence on the total absorptions and refractive index cllanges. The results are significant for designing some important photodetectors and the photonic crystal devices with adjustable photonic band structures.

关键词： coated conductor buffer layer self-epitaxy CeO2

Effect of a Two-Dimensional Periodic Dielectric Background on Complete Photonic Band Gap in Complex Square Lattices

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Chinese Physics Letters 2008年第1期25卷 144-147页

作者：张艳史俊杰 State Key laboratory for mesoscopic Physics and School of Physics Peking University Beijing 100871

A two-dimensional photonic crystal model with a periodic square dielectric background is proposed. The photonic band modulation effects due to the two-dimensional periodic background are investigated in detail. It is found that periodic modulation of the dielectric background greatly alters photonic band structures, especially for the Epolarization modes. The number, width and position of the photonic band gaps sensitively depend on the dielectric constants of the two-dimensional periodic background. Complete band gaps are found, and the dependence of the widths of these gaps on the structural and material parameters of the two alternating rods/holes is studied.

关键词： SPONTANEOUS EMISSION CRYSTALS