arXiv subjects

Adrian Bahri

Publications and source records attributed to Adrian Bahri.

4 recordsLinked to original sources

arXiv2026

Electronic and Magnonic Properties of $g$-Wave Altermagnetism in Intercalated Transition Metal Dichalcogenides

Altermagnetism is a recently identified class of magnetic order characterized by unconventional momentum-dependent spin splitting in the absence of net magnetization, and understanding its electronic and magnetic properties is essential for revealing its fundamental physics and potential applications. In this work we investigate two intercalated transition-metal dichalcogenides, Fe$_{1/4}$NbS$_2$ and V$_{1/3}$NbS$_2$, as candidate altermagnetic materials by using effective tight-binding and spin models complemented by first-principles calculations. We show that the $g$-wave electronic spin splitting originates from bond-dependent hopping anisotropy, leading to material-dependent nodal structures. For the magnetic excitations, the emergence of chiral splitting in the magnon dispersion is controlled by single-ion anisotropy, which manifests as altermagnetic-like nodal structures when spins are oriented along an easy-axis. Conversely, this altermagnetic signature disappears when the spins are aligned in an easy-plane. Beyond linear spin-wave theory, we find that $1/S$ corrections from magnon--magnon interactions preserve the symmetry and nodal structure of the band splitting while generally reducing its magnitude, with strong antiferromagnetic exchange leading to a non-negligible renormalization of the chiral splitting. Our findings establish intercalated transition-metal dichalcogenides as promising platforms for understanding the interplay between crystal symmetry, non-relativistic spin splitting, and magnetic properties in altermagnets.

cond-mat.str-el↗

arXiv2026

Self-Assembled H2NC Molecular Lattices as a Platform for Tunable Quantum Superlattices

Compared to van der Waals moir\'e systems, molecular assembly has emerged as an exciting alternative platform for superlattice engineering via heterointegration. The electronic properties of the self-assembled square lattice monolayer molecular crystal of metal-free naphthalocyanine (H$_2$Nc), in particular the electronic band dispersion and their tunability by metal substrates, remain less explored. Using density functional theory, supported by angle-resolved photoemission and scanning tunneling microscopy, we compare the electronic structure of a free-standing H$_2$Nc monolayer with that of H$_2$Nc lattice assembled on noble metal substrates. In the free-standing film, we identify both nearly flat, molecule-localized states and more dispersive bands, and we show that each can be compactly described by an anisotropic tight-binding Hamiltonian that yields band-resolved hopping anisotropies. We further show theoretically the wide tunability in the inter-site hopping and Coulomb interaction based on dielectric and screening environment, and show two experimental realizations using Ag(100) and Au(111) substrates. On Ag(100), orbital hybridization between molecular frontier states and the substrate drives finite spectral weight at the Fermi level and local interfacial polarization. This hybridization enhances the effective intermolecular hopping roughly thirty-fold, drastically reducing $U/t$. Complementary angle-resolved photoemission spectroscopy resolves substantial interfacial charge redistribution and enhanced bandwidth of the HOMO band, consistent with theoretical predictions. These results clarify how metal substrates and gates convert H$_2$Nc from isolated molecules into a tunable 2D lattice, and highlight molecular superlattices as a promising platform in which the effective interaction parameters can be engineered over a wide range.

cond-mat.mtrl-sci↗

arXiv2024

Altermagnetism and Strain Induced Altermagnetic Transition in Cairo Pentagonal Monolayer

Altermagnetism, a recently discovered class of magnetic order characterized by vanishing net magnetization and spin-splitting band structures, has garnered significant research attention. In this work, we introduce a novel two-dimensional system that exhibits $g$-wave altermagnetism and undergoes a strain-induced transition from $g$-wave to $d$-wave altermagnetism. This system can be realized in an unconventional monolayer Cairo pentagonal lattice, for which we present a realistic tight-binding model that incorporates both magnetic and non-magnetic sites. Furthermore, we demonstrate that non-trivial band topology can emerge in this system by breaking the symmetry that protects the spin-polarized nodal points. Finally, \emph{ab initio} calculations on several candidate materials, such as FeS$_2$ and Nb$_2$FeB$_2$, which exhibit symmetry consistent with the proposed tight-binding Hamiltonian, are also presented. These findings open new avenues for exploring spintronic devices based on altermagnetic systems.

cond-mat.str-el↗

arXiv2021

Real-time simulation of light-driven spin chains on quantum computers

In this work, we study the real-time evolution of periodically driven (Floquet) systems on a quantum computer using IBM quantum devices. We consider a driven Landau-Zener model and compute the transition probability between the Floquet steady states as a function of time. We find that for this simple one-qubit model, Floquet states can develop in real-time, as indicated by the transition probability between Floquet states. Next, we model light-driven spin chains and compute the time-dependent antiferromagnetic order parameter. We consider models arising from light coupling to the underlying electrons as well as those arising from light coupling to phonons. For the two-spin chains, the quantum devices yield time evolutions that match the effective Floquet Hamiltonian evolution for both models once readout error mitigation is included. For three-spin chains, zero-noise extrapolation yields a time dependence that follows the effective Floquet time evolution. Therefore, the current IBM quantum devices can provide information on the dynamics of small Floquet systems arising from light drives once error mitigation procedures are implemented.

cond-mat.mes-hall↗