arXiv subjects

Issam Mahraj

Publications and source records attributed to Issam Mahraj.

4 recordsLinked to original sources

arXiv2026

Theoretical investigation of the photovoltaic properties of MgSnN$_{2}$ for multi-junction solar cells

The orthorhombic crystal structure of the MgSnN$_2$ compound with Pna2$_1$ symmetry has been investigated as a low-cost, non-toxic material for photovoltaic (PV) applications using density functional theory (DFT) and spectroscopic limited maximum efficiency (SLME) calculations. A detailed analysis of the electronic and optical properties was performed using the mBJ semilocal exchange functional. The bandgap of MgSnN$_2$ is found to be 2.45 eV. SLME photovoltaic analysis suggests that a thin film of MgSnN$_2$ with a thickness of 2 $\mu$m can reach an efficiency of 13.17% at room temperature. This efficiency was further improved through the simulation of a multi-junction device, where the tandem configuration increased the efficiency from 12.80% (single-junction) to 22.42%. Furthermore, introducing cation disorder can further reduce the bandgap, enhancing its suitability for solar cell applications.

cond-mat.mtrl-sci↗

arXiv2025

Topological character of the antiferromagnetic EuMg$_{2}$Bi$_{2}$

Antiferromagnetic EuM$_{2}$Pn$_{2}$ compounds, where M is a metal element and Pn is a pnictogen element, have been recognized as candidates for realizing a topologically nontrivial electronic structure. In this paper, we focus on EuMg$_2$Bi$_2$, whose topological nature still remains unclear. We present a comprehensive study based on several experimental and theoretical techniques. Magnetic susceptibility, electrical resistivity, and specific heat capacity measurements confirm the existence of an antiferromagnetic ordering. The electronic band structure was investigated by high-resolution angle-resolved photoemission spectroscopy (ARPES), supported by ab initio calculations. ARPES measurement reveals that the electronic structure of this system is dominated by linearly dispersive hole-like bands near the Fermi level. Theoretical analyses of the electronic band structure indicates that EuMg$_2$Bi$_2$ is a strong topological insulator, which should be reflected in the presence of a metallic surface state. We also theoretically examine the magnetic-field-induced anomalous Hall conductivity, confirming previously reported observations.

cond-mat.mtrl-sci↗

arXiv2025

Phonon Weyl points and chiral edge modes with unconventional Fermi arcs in NbSi$_{2}$

NbSi$_{2}$ crystallizes in the P6$_{2}$22 symmetry, featuring chiral chains of Si atoms. The absence of inversion symmetry, combined with its chiral structure, gives arise to unique physical properties. The breaking of inversion symmetry leads to the emergence of Weyl points, while the chiral structure enables the formation of chiral edge modes. As a result, NbSi$_{2}$ serves as an ideal platform for exploring the interplay between phonon Weyl points and chiral phonon edge modes. For example, we identify the presence of a structure consisting of three Weyl points with a Chern number of $\mathcal{C} = +1$ around the $\bar{\text{K}}$ point. These nodes form unconventional Fermi arcs connecting the $\bar{\Gamma}$ or $\bar{\text{K}}$ points, which mimic an effective Chern number of $\mathcal{C} = -2$.

cond-mat.mtrl-sci↗

arXiv2024

Chiral phononic and electronic edge modes of EuPtSi

Systems with P2$_{1}$3 symmetry are characterized by the realization of chiral edge modes, propagating in one direction along closed loops around some high symmetry points of the Brillouin zone. We study the phononic and electronic properties of EuPtSi, which crystallizes with P2$_{1}$3 symmetry. EuPtSi is also characterized by intriguing magnetic properties, such as the realization of the skyrmion lattice. Here, using ab initio techniques, we study bulk and slab properties of EuPtSi. The bulk phononic and electronic band structures exhibit a spin-1 Weyl point and a charge-2 Dirac point at the $\Gamma$ and R points, respectively. Consequently, the surface states exhibit chiral edge modes. Such features are present in both the phononic and electronic surface spectra. The chiral phononic edge mode is associated with the vibration of the atoms in close vicinity, while the chiral electronic surface states correspond to carrier accumulation at the edge of chiral atomic chains.

cond-mat.mtrl-sci↗