Title:	Magneto-optical response in 2D magnetic crystals
DNr:	NAISS 2026/4-358
Project Type:	NAISS Small
Principal Investigator:	Roman Stepanov <roman.stepanov@lnu.se>
Affiliation:	Linnéuniversitetet
Duration:	2026-02-20 – 2027-03-01
Classification:	10304
Homepage:	https://lnu.se/personal/roman.stepanov/
Keywords:

Abstract

This project aims to investigate magneto-optical and topological response as well as quantum transport in topological insulators (TIs), with an emphasis on a variety of 2D materials and van der Waals (vdW) heterostructures. My primary goal is to employ magnetic TIs where interlayer magnetism, hybridisation, and symmetry breaking mechanism provide a control of topological phases and their electromagnetic response. I plan to use first-principles methods based on density functional theory (DFT) as implanted in VASP and Quantum ESPRESSO (QE) packages. I will also use Wannier90, WannierTools, and WannierBerri packages to construct and analyse tight-binding models, enabling efficient calculations of topological invariants, Berry-curvature–driven response functions, and finally Kerr and Faraday angles. In addition, I will compute quantum-transport characteristics of selected nanostructures and heterostructures using NEGF-based transport workflows. Specific aims and objectives for the coming year (February 2026 – January 2027) are: Magneto-optical effects in layered topological magnets and heterostructures: I will perform a systematic study of Kerr/Faraday rotation angles and related optical Hall responses in magnetic TI  thin films and vdW heterostructures. A key goal is to identify robust regimes where the magneto-optical response provides an unambiguous fingerprint of the underlying topological phase, and to quantify sensitivity to thickness, stacking, interlayer exchange, and symmetry breaking. The work will combine first-principles calculations and effective low-energy models (e.g., coupled Dirac-cone models) to clarify microscopic mechanisms and guide experimentally relevant parameter ranges. Quantum transport in TIs  and vdW heterostructures with pristine 2D crystals and magnetic substrates: I will use tight-binding Hamiltonians and NEGF-based transport workflows to compute conductance and selected non-local transport signatures, and to analyze how they depend on magnetic configuration, interface coupling, and device geometry. Nonlinear Kerr/Faraday response in altermagnets: I will initiate a focused study of nonlinear magneto-optical Kerr and Faraday effects in altermagnetic materials. The objective is to establish symmetry-based selection rules, compute nonlinear Kerr/Faraday spectra from Wannier-based models, and identify material/frequency regimes with enhanced and experimentally accessible nonlinear magneto-optical fingerprints of altermagnetic order. Main supervisor: C. M. Canali (Linnaeus University)