Title:	Computational modeling of solid-state surface and interface properties
DNr:	NAISS 2025/5-546
Project Type:	NAISS Medium Compute
Principal Investigator:	Sophie Weber <sophiewe@chalmers.se>
Affiliation:	Chalmers tekniska högskola
Duration:	2025-10-01 – 2026-10-01
Classification:	10304
Homepage:	https://www.chalmers.se/en/persons/sophiewe/
Keywords:

Abstract

The importance of solid-state surfaces for many applications, from electronics to heterogenous catalysis, has been known for decades. Less established is the fact that surfaces are also a platform for emergent phenomena, such as a net surface magnetization, or a net surface polarization, that are forbidden by symmetry constraints from existing deep inside the material bulk. These emergent surface phenomena have the potential to transform current device architectures, in particular for spintronics applications where the electron spin degree of freedom, in addition to its charge, is used to store and transport information. Although the theoretical concept of low-symmetry surface properties has been been known (but under-recognized) for some time, first-principles calculations that quantitatively predict and characterize these emergent surface properties in realistic materials are still in their infancy. In the ongoing and upcoming projects which will be enabled by this medium compute project, we will use first-principles density functional theory (DFT) supplemented with Wannier-based tight binding models and Monte Carlo simulations to achieve two broad goals related to advancing the qualitative and quantitative understanding of surface phenomena. First we will continue to leverage symmetry analysis combined with the above computational methods to predict and characterize new emergent magnetic, electronic and structural properties at solid-state surfaces, interfaces and in low-dimensional materials. A second, closely related theme is to combine ab-initio calculations with model Hamiltonians to understand how surface effects can manifest in realistic materials subjected to experimental conditions, such as at finite temperatures and under applied electromagnetic fields. A few specific projects for which we plan to use this medium compute project are the following: 1. Symmetry and DFT-based investigation of interface properties, in particular their "penetration" depth away from the interface. (Contingent on a VR grant application; if successful the PhD student would start next year) 2. Combined DFT and Monte Carlo studies of deterministic magnetic-field based domain selection in antiferromagnets (ongoing) 3. Consequences of surface magnetization on the surface electronic structure of antiferromagnets (began this September, project of a PhD student funded from my startup package) 4. Symmetry-guided realization of low-dimensional magnetoelectric quantum magnets: combined high-throughput search with DFT-based evaluation of most promising candidates. Funded by the Nano and Materials Areas of Advance at Chalmers, this project will start in Jan. 2026. I have already hired a postdoc. The broad range of properties to be investigated in this proposal necessitates a variety of methods with differing levels of computational overhead. To account for localized unpaired electrons DFT+U will be used. Constrained, noncollinear DFT will also be leveraged to explore energy landscapes as a function of magnetic. For low-dimensional magnetoelectric properties, we will simulate applied electric fields within DFT at various levels of theory. Tight-binding models using Wannier90 will enable calculations of larger slabs than is tractable within DFT, which may be necessary for certain surface properties. Finally, we will evaluate temperature and field-dependent magnetic properties using Monte Carlo simulations.