Christian Sadem Kenfack

• PhD in Condensed Matter Physics + PhD in Physical Oceanography and Applications
• Professor (Associate) at University of Dschang

In this work, we investigated the mobility and decoherence of bipolaron in transition metal dichalcogenides pseudodot quantum qubit using the Huybrecht method. We investigated the mobility of the bipolaron and the ground and first excited state energies and highlighted that the qubit can be formed in superposition state of the system. The decoheren...

We theoretically study the effect of the quadratic coupling strength on optomechanical systems subjected to a continuous external force. Quadratic coupling strength originates from strong coupling between the optical and the mechanical degrees of freedom. We show that the quadratic coupling strength reduces the amplitude of the dispersion spectra a...

The magnetocaloric Effect (MCE) of a quantum pseudodot was investigated by considering the influence of spin–orbit interaction (SOI). The entropy and internal energy change have been calculated using the Tsallis formulation. Our results reveal that both the SOI effect and external parameters have a significant impact on the entropy and internal ene...

Recent research works on ultra cold quantum gases demonstrated that dipolar Bose–Einstein condensates (BECs) exhibit rich spatiotemporal dynamic where both local and nonlocal interactions are considered. We explore theoretically the possibility of controlling the formation and dynamics of soliton molecules in binary dipolar condensates with spin-or...

We report ab initio DFT calculations to investigate the effect of the BN layer on the electronic and optical properties of graphene. The electronic properties of graphene/h-BN bilayers have been calculated with the Generalized Gradient Approximation (GGA) and modified Becke-Johnson (mBJ) exchange potential. This latter potential is used in the aims...

The relaxation of excitonic polaron and the transport properties in two-dimensional monolayers of transition metal dichalcogenides (TMDCs) such as MoS2, MoSe2, WSe2, and WS2 are investigated under the influence of a magnetic barrier and an electric field using the relaxation-time approximation and the Kubo formula. We find that the presence of magn...

Due to their physical properties and potential importance to the understanding of the electron mobility in a wide variety of materials, polarons are currently the subject of intensive research. Using one of the world most powerfull trapping entity, we investigated the influence of surrounding environment on the dynamic of Fröhlich polaron with the...

We investigate the Magnetocaloric Effect (MCE) of a quantum pseudodt taking into account the effect of spin orbit interaction (SOI). The entropy change and internal energy change been derived using the Tsallis formalism. we observed that the SOI effect and external parameters strongly affect the entropy change and internal energy change of a quantu...

The letter presents a Ginzburg-Landau model of fluctuations in superconductors in the zero-dimensional (0D) limit. The central descriptive tool is a complex order parameter interpreted as a self-consistent field describing the centre-of-mass motion of electrons pairs and highlighting a resistance between Cooper pairs. We describe the temperature an...

We theoretically investigate the properties of exciton-polaron moving through a magnetic barrier in monolayers (1Ls) transition metal dichalcogenides (TMDs): MoS2, WS2, MoSe2, and WSe2. We find that the exciton-polaron has the highest ground state energy in WS2 and the lowest one in MoSe2. It is seen that the magnetic barrier stabilizes the exciton...

Taking into account an infinite confinement potential, including the influence of external electric field applied in different directions, we have systematically examined the different factors that lead to changes in the ground state binding energy between the hydrogen impurity and the electron, which are confined in a wedge-shaped cylindrical quan...

In this paper, we study the impacts of an initial axial force and the surface effects on the dynamic characteristics of an embedded bioliquid filled microtubule (MT) under a walking motor protein. We model the microtubule using the orthotropic Timoshenko Beam (TB) model. The impact of the surrounding cytoplasm is considered by modelling it as a two...

This work focused on studying the energy changes due to a cylindrical quantum dot (CQD) deformation compared to a toroidal quantum dot (TQD). The energies and the electronic states are studied as a function of the TQD geometrical parameters(RC, Rg, φ0, θ0). The transition energy between the ground and first excited states is also studied. In the fr...

We developed and obtained close-form solutions for the buckling growth rate of microtubule (MT) bundles using the Timoshenko beam theory. We took into consideration the surface effects and the Poisson’s ratio of the microtubules surrounded by neighbouring filaments in the viscous cytosol. We developed the motion equation by using the modified coupl...

The relaxation and the transport of excitonic polaron are theoretically investigated in two-dimensional (2D) monolayer (ML) transition metal dichalcogenides (TMDCs): MoSe2, WSe2, WS2, MoS2. It is found that the exciton-polaron relaxation time occurs when the exciton effective kinetic energy is higher than phonon energy. For each TMDC, it decreases...

In this paper, we study the dynamical properties of the exciton-polaron in the microtubule. The study was carried out using a unitary transformation and an approximate diagonalization technique. Analytically, the modeling of exciton-polaron dynamics in microtubules is presented. From this model, the ground state energy, mobility, and entropy of the...

This paper gives a detailed description of a high-performance polariton condensate for a quantum mechanical two-level system (TLS). We propose a transition metal dichalcogenides (TMDs) setup and theoretically carry out the spectroscopy of these polariton condensates. Through theoretical and numerical analysis, we obtain many features in two dimensi...

We investigate the dynamics and decoherence of the exciton polaron in a 2D transition metal dichalcogenides modulated by a magnetic field barrier. Using the Huybrechts method and an approximate diagonalization of exciton-phonon operators is performed to derive the fundamental energy, the first excited state energy, the effective mass and the mobili...

We studied the optical signature of bipolaron and its effects on the bandgap modulation in the single-layer Transition Metal Dichalcogenides (TMDs) under magnetic field. Using the Huybrecht method, we derived the ground state energies in the modified zero Landau levels for all Fröhlich coupling constants. We take into account both intrinsic longitu...

Optical bipolaron properties in the symmetric quantum dot were investigated using the Lee-Low-Pines-Huybrechts method and the Tokuda linear combination operator method. Algebraic expressions are derived for the energies of the fundamental and first excited states, the effective mass, mobility, binding energy and oscillation period of the optical bi...

In this paper, we theoretically investigate the effect of Electron–phonon coupling on the dynamic and optical absorption of exciton-polaron in Transition Metal Dichalcogenides (MoS2, WS2, MoSe2, and WSe2) under magnetic field using Huybrechts method. Both surface optical phonon mode and longitudinal phonon mode are taken into account. It is seen th...

In the present paper, we theoretically study the dynamics and decoherence of polaron in monolayer graphene. We obtain the energies of ground and first excited states by using linear combination operator and applying a variational method of Pekar. Then, we evaluate some polaron's properties such as the effective mass, the mobility, optical absorptio...

In this paper, we study the microtubule as a ferroelectric system. The behaviour of microtubules around the critical temperature was evaluated, and the effect of the electric field produced by the microtubules on its environment was determined. Also, the mean-field theory approximation (MFTA) was used to evaluate the total polarization and free ene...

We studied the optical signature of bipolaron and its effects on the bandgap modulation in the single-layer Transition Metal Dichalcogenides (TMDs) under magnetic field. Using the Huybrecht method, we derived the ground state energies in the modified zero Landau levels for all Fröhlich coupling constants. We take into account both intrinsic longitu...

We study in this paper, the dynamic and decoherence of polaron in transition metal dichalcogenides (TMDs) under electric field using Lee–Low Pines (LLP) method. We derived the fundamental and first excited states energies of polaron, the mobility in the two states and the lifetime of polaron. Due to the polaron’s superposition states in TMDs, the q...

Careful analysis of long-term wind data in a broad area is essential to estimate the wind energy potential of a region. For this purpose, knowledge of wind speed distribution is an essential task. This paper proposes a comprehensive statistical evaluation of monthly, annual, and interannual variabilities of mean wind speeds and wind power densities...

In this work, we use the variational method to investigate thermal properties and optical absorption of polaron in monolayer graphene under laser field. We have shown that the energies and the optical absorption of the system strongly depend on laser parameters and graphene characteristics. We found that the simple model adopted to calculate the op...

In this work, we are studying thermodynamics properties and optical absorption of bipolaron in graphene under a laser field using the variational method. We obtain the ground and first excited states of the bipolaron which strongly depend on laser parameter and graphene characteristics. It is seen that the optical absorption of a bipolaron in graph...

The dynamics and decoherence of excitonic polaron in a two-dimensional monolayer transition metal dichalcogenides (TMDCs) in quantum dot have been investigated using a variational method. We focused on confinement and temperature effects on dynamics properties and decoherence of exciton polaron, and found that the entropy increases with increasing...

This work treats entropy and heat capacity of a monolayer transition metal dichalcogenide quantum dot under magnetic field using the canonical ensemble approach. We consider four following TMDs: MoSe2, MoS2, WSe2 and WS2. At low temperature heat capacity increases steadily, shows a shoulder and thereafter becomes constant for high temperatures. MoS...

We have investigated the dynamic of cooled and trapped polariton state using Landau–Zener–Stückelberg interferometry theory (LZSIT). The effects of exciton–cavity coupling and the laser cooling over the qubit dynamics are analyzed in multi-crossing scenarios, supporting some of our basic results (Kenfack et al. in Comput Condens Matter 11:47–54, 20...

Optical bipolaron’s stability and decoherence confined in the symmetric quantum dot are investigated utilizing the modified Lee, Low, and Pines variational method. The binding energy of optical bipolaron in symmetrical quantum dot systems is obtained by computing the energy of the fundamental state, the energy of the ground state of the single pola...

Microtubules as essential biopolymers implicated into electrical intracellular transport open a lot of questions about their intrinsic character of dynamic instability. Both experimental and theoretical investigations are used to understand their behavior in order to mimic and build powerful and smart biomaterials. So, in this paper, by analytical...

We investigate the dynamics of microtubules (MTs) under the influence of the electric field using the Ising model. The mean-field theory is used to compute the thermodynamic properties of the model such as polarization, critical temperature, and free energy in the absence and presence of the external electric field. The results show that the magnit...

We studied the effect of polar vibration modes on optical absorption of polaron and the rate of disorder in a graphene monolayer. Our investigation focused more particularly on the role played by phonons. We found that the amplitude of optical absorption decreases with increasing photon energy and with increasing magnetic field. We also found that...

In this paper, we have investigated the lifetime, mobility and effective mass of polaron and bipolaron in graphene under laser field by using the well-known Lee–Low–Pines transformations. In this study, it is seen that the laser affects mostly the dynamics parameters of polaron and bipolaron in graphene. We found that the laser reduces the lifetime...

We study the dynamic of magneto-polaron condensate in monolayer two dimensional (2D) transition metal dichalcogenides (TMDs) materials of 2H types in triangular quantum well potential. Within both the quantum mechanical Schrödinger approach (QMSA) and the improved Wigner-Brillouin theory (IWBT), Landau energies levels (LELs) are derived. We have sh...

In this paper, we investigated the possible formation of polarons and bipolarons in graphene under a laser field. The LLP framework is used to solve the stated problem. We see that the laser greatly affects the properties of the polaron in graphene. We show that the laser also increases the first energy level of the polaron in the structure. It is...

This work presents the important role played by the spin-orbit interaction in nanostructures such as disk quantum dot when subjected to an external field. Here by using the LLP variational method, the Rashba effect on polaron in this nanostructure with Gaussian confinement potential under electromagnetic field is investigated. The polaron ground, f...

This work treats the polaron's magnetic and thermal properties with delta confinement and interacting with external magnetic and electric areas have been investigated under Rashba effect. We used the Schrodinger equation to find the wave function and the quantified energies of the system. We found that the corresponding wave function can be separat...

Cells actively modify their behavior in on account of changes in their environment. The most important intrinsic parameter related to the intracellular environment is the temperature, the variations of which modify the dynamical behaviors of biomolecules. Indeed, an increase in temperature leads to an increase in fluidity which can damage the prote...

The chemical properties of the hydrogen molecule under a magnetic field in a transverse configuration and in the presence of phonons are investigated using the Density Functional Theory. The hydrogen molecule is considered as a two-electron system confined in a Coulomb type parabolic external potential. It is shown that the electron density and the...

This paper gives a detailed description of a high-performance tunneling wire “flying qubit” for a quantum mechanical two-level system. We propose a simple double-wire interferometer setup and theoretically carry out the spectroscopy of these flying qubits. As such, we present a tight binding theoretical model which effectively mimicks the experimen...

The possibility of controlling a polaron in an asymmetric quantum dot with external magnetic field and laser light is examined in this paper. Analytical studies are done using a modified Lee-Low-Pines method. We calculate the fundamental and first state energies which form a single qubit and further determine the probability density and the Shannon...

An investigation into the superconducting order parameter thermodynamic fluctuations and their manifestations on paraconductivity in cuprate superconductors is done using a renormalized Gaussian approach based on the Ginzburg–Landau theory. The temperature dependence of paraconductivity is affected by repulsive interactions between Cooper pairs and...

The contributions of bulk and surface phonons to the properties of a polaron in a Zn1 −XCdXSe∕ZnSe heterojunction confined in a triangular potential have been studied using the Lee-Low-Pines variational method and the Tokuda linear-combination operator method. We obtain expressions for the wave function of the system, the ground state energy, effec...

This study evaluates the ability of the Regional Climate Model (RegCM4) to reproduce the observed rainfall and wind over West and Central Africa (WCA) during two contrasting years of the Atlantic Cold Tongue (ACT): the very cold in 1992 and very warm in 2007 depicted by the Caniaux et al. (2011)'s index. The convective schemes of Kuo, Massachusetts...

An interaction between matter and light remains the most important physical mechanism which open path to explore the fundamental principles of quantum mechanics. In this paper, the dynamical behavior of the system of cooled and trapped polariton is studied. In particular, we analytically and numerically studied decoherence in a system of cooled pol...

We have studied the transition probability and decoherence time of levitating polaron in helium film thickness. By using a variational method of Pekar type, the ground and the first excited states of polaron are calculated above the liquid-helium film placed on the polar substrate. It is shown that the polaron transits from the ground to the excite...

An interaction between electrons with photon is an important phenomenon in physics and, particularly, condensed matter and theoretical physics. The result of this interaction yields a quasi-particle called, polariton. In this study we investigated the role of polariton in cooling and trapping processes. We observed that the probability of finding c...

We study the quantum tunneling of a two-level multi-crossing system in an accelerating one-dimensional optical parabolic potential manifested in a 3D heterostructure magnetic quantum wire. By direct integration using the Dynamic matrix approach (DMA), we establish the time and magnetic field dependencies of the generalized analytic expressions of t...

In this paper, we investigate decoherence caused by a system of polaron in asymmetric quantum wire (AQW) using an all coupling variational method. We have derived the ground and first excited energy states, which describe the two states of polaron in an AQW. The two quantum states formed by the polaron in quantum wire can form a quantum bit due to...

Using Pekar variational method, Eigen energies of the ground and first excited states of the polaron in triangular bound and Coulomb potential quantum dot are derived in view of investigating the density of probability, the decoherence time and the Shannon entropy. Numerical analysis show that the decoherence time is decreasing function of polaron...

In this paper, we examine the time evolution of the quantum mechanical state of a polaron in asymmetry cylindrical quantum dot using the Pekar type variational method under the condition of electric-LO-phonon and magnetic-LO-phonon strong coupling. We obtain the Eigen energies and the Eigen functions of the ground state and the first excited state,...

Principal Component Analysis (PCA) is one of the popular statistical methods for feature extraction. The neural network model has been performed on the PCA to obtain nonlinear principal component analysis (NLPCA), which allows the extraction of nonlinear features in the dataset missed by the PCA. NLPCA is applied to the monthly Sea Surface Temperat...

Using the Pekar variational method, the ground and first excited state energy of the magnetopolaron in a RbCl triangular quantum dot are derived. This system in a quantum dot is treated as a two-level quantum dot system. The density of probability and the Shannon entropy are derived and the influence of the magnetic field on the Shannon entropy is...

We studied the effect of the tunable potential and decoherence of polaron in nanostructures. We have arbitrarily chosen eight potentials: the elliptical potential, square potential, triangular potential, the quadratic potential, the delta potential, the Gaussian potential, the pseudo-harmonic potential and Coulombic potential. In order to evaluate...

The ground and first excited state energy of bound polaron in RbCl triangular quantum dot are obtained by employing the linear combination operator and unitary transformation methods. Effects of temperature and electric field, the influence of polaron radius and polar angle on lifetime and energy levels are studied. Numerical results show the decre...

IMPACT OF ANTHROPOGENIC AEROSOLS ON CLIMATE VARIABILITY OVER CENTRAL AFRICA using RegCM4

Landau-Zener-Stückelberg interferometry is extensively investigated in a 3D heterostructure magnetic quantum wire. Local magnetic fields are used to coherently manipulate and control a qubit's quantum state. For our numerical calculations, a parabolic confinement is assumed. Energy eigenvalues, non-adiabatic and adiabatic transition probabilities a...

Using the Pekar variational method, the effects of the temperature, impurity and electromagnetic fields on the transition are investigated through the eigenenergies of the ground and first-excited states of the polaron in a triangular potential quantum dot. Those parameters are essential for the transition of the polaron from the ground state to th...

In the following study, the time evolution of the quantum mechanical state of a magnetopolaron using the Pekar type variational method on the electric-LO-phonon was considered. A strong coupling of polaron in triangular RbCl quantum dot with Coulomb impurity was duly derived. The Eigen energies and the Eigen functions of the ground state and the fi...

In this study, version 4 of the regional climate model (RegCM4) is used to perform 6 years simulation including 1 year for spin-up (from January 2001 to December 2006) over Central Africa using four convective schemes: The Emmanuel scheme (MIT), the Grell scheme with Arakawa-Schulbert closure assumption (GAS), the Grell scheme with Fritsch-Chappell...

In the present study, we have investigated the impacts of anthropogenic aerosols on some relevant atmospheric parameters such as temperature, precipitation, wind and shortwave radiation. For this aim, we use the International Centre for Theoretical Physics (ICTP) regional climate model version 4 named RegCM4. Two sets of simulations with 1 year of...

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 RbCl triangular quantum dot. We obtain the eigenenergies, and the eigenfunctions of the ground state, and the first excited state respectivel...

The real interaction between matter and electromagnetic radiation is too complicated for a complete theoretical investigation. In this paper, we study phase transition of polariton and magnetopolariton in semiconductor microcavity. We have analyzed the polariton and magnetopolariton phase transition via the path integral approach in Dicke model. Nu...

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 consta...

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 cou...

In this paper, we investigate the time evolution of the quantum mechanical state of a polaron using the Pekar type variational method on the electric-LO-phonon and the magnetic-LO-phonon strong coupling in a quantum dot. We obtain the Eigen energies and the Eigen functions of the ground state and the first excited state, respectively. In a quantum...

We investigated the influence of electric field and magnetic field on the ground state energy of polaron 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 m...

We demonstrate that some specific problems of Landau–Zener transitions in a qubit coupled to an environment (problems designed as dissipative) can be matched onto the frame of the original problem without dissipation, providing an appropriate Lie algebra. Focusing on the origin of quantum noises, the cases of bosonic and spin baths are considered a...

We investigate the Landau–Zener (LZ) like dynamics of decaying two- and three-level systems with decay rates ${{\Gamma }_{1}}$ and ${{\Gamma }_{2}}$ for levels with minimum and maximum spin projection. Non-adiabatic and adiabatic transition probabilities are calculated from diabatic and adiabatic bases for two- and three-level systems. We extend th...

In this paper, we investigated the influence of electric field on the ground state energy of polaron in spherical semiconductor quantum dot (QD) using 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 confinement lengths. The modulation of the elec...

In this paper, we investigate the influence of an electric field 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 an increase of the ground state energy with the increase of the electric field and the confinement lengths. The modulation of...

In this paper, we investigate the influence of the magnetic field and the temperature on the ground state energy of a weak coupling polaron in a spherical semiconductor quantum dot (QD) using the modified LLP method. The ground state energy of a weak coupling magneto-optical polaron is split into sub-energy levels and there is the degeneracy of the...

Principal Component Analysis (PCA) is one of the popular statistical methods for feature extraction. The neural network model has been performed on the PCA to obtain nonlinear principal component analysis (NLPCA), which allows the extraction of nonlinear features in the dataset missed by the PCA. NLPCA is applied to the monthly Sea Surface Temperat...

Exact analytical solutions to the dissipative time-dependent Schr\"odinger equation are obtained for a decaying two-state system with decay rates $\Gamma_{1}$ and $\Gamma_{2}$ for levels with extremal spin projections. The system is coherently driven with a pulse whose detuning is made up of two parts: a time-dependent part (chirp) of hyperbolic-ta...

An investigation of the spatial fluctuations and their manifestations in the vicinity of the quantum critical point within the framework of the renormalized $\phi^{4}$ theory is proposed. Relevant features are reported through the Ginzburg-Landau-Wilson (GLW)-based calculations, combined with an efficient non perturbative technique. Both the dimens...

We examine the magnetopolaron state in a cylindrical quantum dot with a transverse parabolic potential and a high rectangular potential well in the longitudinal direction. The quadratic dependence of the magnetopolaron energy versus Fröhlich electron–phonon coupling constant for different cyclotron radii and constant structure radius is modulated b...

A Feynman path integration approach is systematically applied to the polaron problem for the tubular geometry. The method represents a Gaussian approximation. The main quasi particle characteristics of the Fröhlich polaron, namely, the ground state energy and the effective mass are derived for two approaches. Numerical results are obtained with the...

We investigate the effect of plasmon screening on the polaron characteristics following the Feynman variational method and find that the screening considerably reduces the polaron characteristics, as plasmon density increases. We establish that the factor contributing to this screening not only depends on the concentration, but also on the anisotro...