arXiv subjects

S. Bekhechi

Publications and source records attributed to S. Bekhechi.

9 recordsLinked to original sources

arXiv2025

A computational study of thermoelectric conversion in the PbSe$_{x}$Te$_{1-x}$ semiconductor alloys

The present theoretical study focuses on the structural, electronic and thermoelectric properties of PbTe, PbSe and their ternary alloys PbSe$_{x}$Te$_{1-x}$, using the density functional theory (DFT) by the full potential linearised augmented plane wave (FP-LAPW) method implemented in Wien2k code. Structural properties were performed by using the generalized gradient approximation of Perdew Burke and Ernzenhof (GGA-PBE) scheme. The results show that the calculated lattice parameters are in good agreement with theoretical data previously obtained. For electronic properties, we noticed that for all the compounds of PbSe$_{x}$Te$_{1-x}$, we have a direct band gap in L point. For thermoelectric properties, we used BoltzTraP2 code and Gibbs2 code. Our results show that the PbSe$_{x}$Te$_{1-x}$ compounds have reached a value of 2.55 for the figure of merit, which indicates that our material is a good thermoelectric candidate.

cond-mat.mtrl-sci↗

arXiv2020

Study of the Ashkin Teller model with spins $S$ = $1$ and $σ$ = $3/2$ subjected to different crystal fields using the Monte-Carlo method

Using the Monte-Carlo method, we study the magnetic properties of the Ashkin-Teller model (ATM) under the effect of the crystal field with spins $S = 1$ and $σ= 3/2$. First, we determine the most stable phases in the phase diagrams at temperature $T = 0$ using exact calculations. For higher temperatures, we use the Monte-Carlo simulation. We have found rich phase diagrams with the ordered phases: a Baxter $3/2$ and a Baxter $1/2$ phases in addition to a $\left\langle σS\right\rangle$ phase that does not show up either in ATM spin 1 or in ATM spin $3/2$ and, lastly, a $\left\langle σ\right\rangle = 1/2$ phase with first and second order transitions.

cond-mat.stat-mech↗

arXiv2016

Method of computation of energies in the fractional quantum Hall effect regime

In a previous work, we reported exact results of energies of the ground state in the fractional quantum Hall effect (FQHE) regime for systems with up to $N_{\text{e}} = 6$ electrons at the filling factor $ν= 1/3$ by using the method of complex polar coordinates. In this work, we display interesting computational details of the previous calculation and extend the calculation to $N_{\text{e}} = 7$ electrons at $ν= 1/3$. Moreover, similar exact results are derived at the filling $ν= 1/5$ for systems with up to $N_{\text{e}} = 6$ electrons. The results that we obtained by analytical calculation are in good agreement with their analogues ones derived by the method of Monte Carlo in a precedent work.

cond-mat.str-el↗

arXiv2015

Numerical study of the spin-3/2 Ashkin-Teller model

The study of the Ashkin-Teller model (ATM) of spin-3/2 on a hypercubic lattice is undertaken via Monte Carlo simulation. The phase diagrams are displayed and discussed in the physical parameter space. Rich physical properties are recovered, namely the second order transition and multicritical points. The phase diagrams have been obtained by varying the strength describing the four spin interaction and the single ion potential. This model shows a new high temperature partially ordered phase, called $\langle S\rangle$ and a new Baxter 3/2 ground state which do not exist either in the spin-1/2 ATM or in the spin-1 ATM.

cond-mat.stat-mech↗

arXiv2006

Short-time dynamics of a family of XY noncollinear magnets

Critical scaling and universality in the short-time dynamics for antiferromagnetic models on a three-dimensional stacked triangular lattice are investigated using Monte Carlo simulation. We have determined the critical point by searching for the best power law for the order parameter as a function of time and measured the critical exponents. Our results indicate that it is possible to distinguish weak first-order from second-order phase transitions and confirm that XY antiferromagnetic systems undergo a (weak) first order phase transition.

cond-mat.stat-mech↗

arXiv2004

Chiral mixed phase in disordered 3d Heisenberg models

Using Monte Carlo simulations, we compute the spin stiffness of a site-random 3d Heisenberg model with competing ferromagnetic and antiferromagnetic interactions. Our results for the pure limit yield values of the the critical temperature and the critical exponent $ν$ in excellent agreement with previous high precision studies. In the disordered case, a mixed "chiral" phase is found which may be in the same universality class as 3d Heisenberg spin glasses.

cond-mat.stat-mech↗

arXiv2003

Damage spreading in two dimensional geometrically frustrated lattices: the triangular and kagome anistropic Heisenberg model

The technique of damage spreading is used to study the phase diagram of the easy axis anisotropic Heisenberg antiferromagnet on two geometrically frustrated lattices. The triangular and kagome systems are built up from triangular units that either share edges or corners respectively. The triangular lattice undergoes two sequential Kosterlitz-Thouless transitions while the kagome lattice undergoes a glassy transition. In both cases, the phase boundaries obtained using damage spreading are in good agreement with those obtained from equilibrium Monte Carlo simulations.

cond-mat.stat-mech↗

arXiv2003

Low Temperature Static and Dynamic Behaviour of the Easy-Axis Heisenberg Antiferromagnet on the Kagome Lattice

The antiferromagnetic Heisenberg model with easy-axis exchange anisotropy on the Kagome lattice is studied by means of Monte Carlo simulations. From equilibrium properties, we find that the values of the critical exponents associated with the magnetization at the critical temperature $T_c$ vary with the magnitude of the anisotropy. On the other hand, the spin-spin autocorrelation functions have a stretched exponential behavior with a power law divergence of the relaxation time at a glass-like temperature $T_g \sim T_c$. From non-equilibrium dynamics at a fixed temperature below $T_g$, aging effects are found which obey the same scaling laws as in spin glasses and polymers.

cond-mat.stat-mech↗

arXiv2003

Off Equilibrium Study of the Fluctuation-Dissipation Relation in the Easy-Axis Heisenberg Antiferromagnet on the Kagome Lattice

Violation of the fluctuation-dissipation theorem (FDT) in a frustrated Heisenberg model on the Kagome lattice is investigated using Monte Carlo simulations. The model exhibits glassy behaviour at low temperatures accompanied by very slow dynamics. Both the spin-spin autocorrelation function and the response to an external magnetic field are studied. Clear evidence of a constant value of the fluctuation dissipation ratio and long range memory effects are observed for the first time in this model. The breakdown of the FDT in the glassy phase follows the predictions of the mean field theory for spin glasses with one-step replica symmetry breaking.

cond-mat.stat-mech↗