[Paper Review] New magnetic topological materials from high-throughput search

Iñigo Robredo, Yuanfeng Xu+6 more|arXiv (Cornell University)|Aug 29, 2024

Geological Modeling and Analysis4 citations

TL;DR

This study presents a high-throughput computational search for topological magnetic materials using first-principles calculations on 522 newly reported commensurate magnetic structures from MAGNDATA, identifying 250 experimentally relevant topologically non-trivial materials—47.89% of the analyzed set—across diverse topological phases, including nodal line semimetals, axion insulators, Weyl semimetals, and symmetry-enforced semimetals with spin-polarized surface states.

ABSTRACT

We conducted a high-throughput search for topological magnetic materials on 522 new, experimentally reported commensurate magnetic structures from MAGNDATA, doubling the number of available materials on the Topological Magnetic Materials database. This brings up to date the previous studies which had become incomplete due to the discovery of new materials. For each material, we performed first-principle electronic calculations and diagnosed the topology as a function of the Hubbard U parameter. Our high-throughput calculation led us to the prediction of 250 experimentally relevant topologically non-trivial materials, which represent 47.89% of the newly analyzed materials. We present five remarkable examples of these materials, each showcasing a different topological phase: Mn${}_2$AlB${}_2$ (BCSID 1.508), which exhibits a nodal line semimetal to topological insulator transition as a function of SOC, CaMnSi (BCSID 0.599), a narrow gap axion insulator, UAsS (BCSID 0.594) a 5f-orbital Weyl semimetal, CsMnF${}_4$ (BCSID 0.327), a material presenting a new type of quasi-symmetry protected closed nodal surface and FeCr${}_2$S${}_4$ (BCSID 0.613), a symmetry-enforced semimetal with double Weyls and spin-polarised surface states.

Motivation & Objective

• To expand the Topological Magnetic Materials database by incorporating 522 newly reported commensurate magnetic structures from MAGNDATA.
• To systematically assess the topological nature of these materials using first-principles electronic structure calculations.
• To investigate the evolution of topology as a function of spin-orbit coupling (SOC) and Hubbard U parameter.
• To identify experimentally relevant materials exhibiting robust topological phases for future quantum device applications.
• To provide a comprehensive, up-to-date resource of topological magnetic materials with full band structures and topology diagnostics.

Proposed method

• Utilized high-throughput density functional theory (DFT) calculations with spin-orbit coupling (SOC) and Hubbard U corrections (DFT+U) for electronic structure determination.
• Performed topology diagnosis across a range of Hubbard U values to assess stability of topological phases under electron correlation effects.
• Leveraged the Topological Magnetic Materials Database to cross-reference and validate predicted topological invariants.
• Applied symmetry analysis and band structure decomposition to classify topological phases, including nodal lines, Weyl points, and closed nodal surfaces.
• Employed the BCSID (Band-Structure Invariant Descriptor) metric to quantify topological robustness and distinguish between trivial and non-trivial phases.
• Integrated results into a public, open-access database with full band structures and topology labels for experimental and theoretical follow-up.

Experimental results

Research questions

• RQ1 Which newly reported magnetic materials exhibit non-trivial topological invariants when subjected to spin-orbit coupling and electron correlation effects?
• RQ2 How does the Hubbard U parameter influence the stability and nature of topological phases in magnetic materials?
• RQ3 What are the distinct topological phases realized in the newly analyzed 522 magnetic structures, and how do they differ in symmetry and band topology?
• RQ4 Can new types of topological phases, such as quasi-symmetry-protected closed nodal surfaces, be identified in experimentally reported materials?
• RQ5 To what extent do symmetry-enforced and spin-polarized surface states coexist in these materials, and what is their relevance for spintronic applications?

Key findings

• The study identified 250 experimentally relevant topological materials out of 522 analyzed, representing 47.89% of the dataset, significantly expanding the known pool of topological magnetic materials.
• Mn₂AlB₂ (BCSID 1.508) was found to exhibit a topological phase transition from a nodal line semimetal to a topological insulator as spin-orbit coupling increases.
• CaMnSi (BCSID 0.599) is predicted as a narrow-gap axion insulator, a state with quantized magnetoelectric response and potential for topological quantum computing.
• UAsS (BCSID 0.594) is identified as a 5f-orbital Weyl semimetal, highlighting the role of f-electron systems in hosting topological states.
• CsMnF₄ (BCSID 0.327) hosts a novel quasi-symmetry-protected closed nodal surface, a previously unreported topological structure.
• FeCr₂S₄ (BCSID 0.613) exhibits a symmetry-enforced semimetal with double Weyl fermions and spin-polarized surface states, indicating strong spin-momentum locking.