The study of magnetic topological semimetals by first principles calculations

Jinyu Zou,Zhuoran He,Gang Xu

doi:10.1038/s41524-019-0237-5

Jinyu Zou, Zhuoran He + Show 1 more

Open Access

https://doi.org/10.1038/s41524-019-0237-5

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Abstract

Magnetic topological semimetals (TSMs) are topological quantum materials with broken time-reversal symmetry (TRS) and isolated nodal points or lines near the Fermi level. Their topological properties would typically reveal from the bulk-edge correspondence principle as nontrivial surface states such as Fermi arcs or drumhead states, etc. Depending on the degeneracies and distribution of the nodes in the crystal momentum space, TSMs are usually classified into Weyl semimetals (WSMs), Dirac semimetals (DSMs), nodal-line semimetals (NLSMs), triple-point semimetals (TPSMs), etc. In this review article, we present the recent advances of magnetic TSMs from a computational perspective. We first review the early predicted magnetic WSMs such as pyrochlore iridates and HgCr2Se4, as well as the recently proposed Heusler, Kagome layers, and honeycomb lattice WSMs. Then we discuss the recent developments of magnetic DSMs, especially CuMnAs in Type-III and EuCd2As2 in Type-IV magnetic space groups (MSGs). Then we introduce some magnetic NLSMs that are robust against spin–orbit coupling (SOC), namely Fe3GeTe2 and LaCl (LaBr). Finally, we discuss the prospects of magnetic TSMs and the interesting directions for future research.

Highlights

The classification of material phases and description of phase transitions in condensed matter physics have long been given by the Landau theory of spontaneous symmetry breaking, with different phases described by different local order parameters
We review the prediction of magnetic Dirac semimetals (DSMs) CuMnAs and EuCd2As2, in which the “magnetic symmetry” causing Kramers degeneracy are IT and IτT
Topological semimetals extend the topological classification of materials from insulators to metallic systems, and have become one of the most attractive fields of study in condensed matter npj Computational Materials (2019) 96 physics in recent years

Summary

INTRODUCTION

The classification of material phases and description of phase transitions in condensed matter physics have long been given by the Landau theory of spontaneous symmetry breaking, with different phases described by different local order parameters. 1.5 eV, as shown, c, the band structure of AIAO magnetic order calculated by LSDA + SO + U demonstrates 24 Weyl nodes in BZ related by three fold rotation symmetry (same chirality) and IS (opposite chirality). The magnetic frustration, electronic correlation and strong SOC of the 5d orbitals in transition metal elements are crucial for understanding the origin of the WSM phase in pyrochlore iridates, and are a treasury of other topological phenomena such as topological insulators, axion insulators and topological Mott insulators.[92,93]. WSM phase have not been directly confirmed by experiment, the study on pyrochlore iridates through varies of theoretical methods[96–100] and indirect experimental signals[101–103] is lasting to shed light on the Weyl nodes and their stabilities. CdCr2Se4 very well.[113,114] As for HgCr2Se4, The same LDA + U calculations shows that the band inversion remains unless the U is unreasonably large (>8.0 eV)

When considering the new low-energy states at Γ are

DISCUSSION AND OUTLOOK