arXiv subjects

Mohammad Mortezaei Nobahari

Publications and source records attributed to Mohammad Mortezaei Nobahari.

3 recordsLinked to original sources

arXiv2025

Photoinduced topological phase transition in monolayer 1T$^\prime$-MoS$_2$

We investigate the nonequilibrium topological phases of monolayer 1T$^\prime$--MoS$_2$ under high-frequency circularly polarized driving using a low-energy $k\!\cdot\!p$ Hamiltonian combined with a van Vleck expansion. The off-resonant field generates spin- and valley-dependent mass corrections that reshape the Berry curvature profile and shift the conditions for band inversion. By evaluating the quasienergy bands, Berry curvatures, Hall conductivities, and spin- valley-resolved Chern numbers, we identify a sequence of light-controlled topological transitions marked by well-defined gap closings. Depending on the Floquet coupling strength and the electric-field parameter, the system evolves between the equilibrium quantum spin Hall (QSH) state and a set of driven phases including spin-polarized quantum Hall insulator (S-QHI), quantum valley Hall (QVH or BI) and photo-induced quantum Hall insulator (P-QHI) regimes. The results establish 1T$^\prime$--MoS$_2$ as a tunable platform where circular driving selectively manipulates spin and valley degrees of freedom, enabling controlled access to non-equilibrium topological phases in transition-metal dichalcogenides.

cond-mat.mes-hall↗

arXiv2025

Topological phase transition in monolayer 1T$^{\prime}$-MoS$_2$

1T$^{\prime}$ phase of the monolayer transition metal dichalcogenides has recently attracted attention for its potential in nanoelectronic applications. We theoretically prove the topological behavior and phase transition of 1T$^{\prime}$-MoS$_2$ using $k.p$ Hamiltonian and linear response theory. The spin texture in momentum space reveals a strong spin-momentum locking with different orientations for the valence and conduction bands. Also, Berry curvature distributions around the Dirac points highlight the influence of $α$ parameter demonstrating a topological phase transition in 1T$^\prime$-MoS$_2$. For $α<1$ the spin Hall conductivity is the only non-zero term $(C_s=1$ and $C_v=0)$, corresponding to a quantum spin Hall insulator (QSHI) phase, while for $α>1$, valley Hall conductivity prevails, indicating a transition to a band insulator (BI). Further analysis explores the spin-valley-resolved Hall conductivity and Chern numbers across varying values of $α$, $V$, and Fermi energy, uncovering regions of non-trivial and trivial topological phases (TTP) and the role of the edge modes. The zero total Nernst coefficient across energy ranges suggests strong cancellation between spin and valley contributions, providing insights into the material's potential for thermoelectric applications and spintronic devices.

cond-mat.mes-hall↗

arXiv2024

Spin-Hall conductivity and optical characteristics of noncentrosymmetric quantum spin Hall insulators: the case of PbBiI

Quantum spin Hall insulators have attracted significant attention in recent years. Understanding the optical properties and spin Hall effect in these materials is crucial for technological advancements. In this study, we present theoretical analyses to explore the optical properties, Berry curvature and spin Hall conductivity of pristine and perturbed PbBiI using the linear combination of atomic orbitals and the Kubo formula. The system is not centrosymmetric and it is hosting at the same time Rashba spin-splitting and quantized spin Hall conductivity. Our calculations reveal that the electronic structure can be modified using staggered exchange fields and electric fields, leading to changes in the optical properties. Additionally, the spin Berry curvature and spin Hall conductivity are investigated as a function of the energy and temperature. The results indicate that due to the small dynamical spin Hall conductivity, generating an ac spin current in PbBiI requires the use of external magnetic fields or magnetic materials.

cond-mat.mes-hall↗