Computational discovery of two-dimensional rare-earth iodides: promising ferrovalley materials for valleytronics

Journal Article · Fri Dec 23 00:00:00 EST 2022 · 2D Materials

DOI:https://doi.org/10.1088/2053-1583/acab72· OSTI ID:1922633

Sharan, Abhishek  ^[1]; Lany, Stephan  ^[2]; Singh, Nirpendra  ^[1]

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1. Khalifa University of Science and Technology, Abu Dhabi (United Arab Emirates)
2. National Renewable Energy Laboratory (NREL), Golden, CO (United States)

Two-dimensional Ferrovalley materials with intrinsic valley polarization are rare but highly promising for valley-based nonvolatile random access memory and valley filter devices. These ferromagnetic materials exhibit valleys at or near the Fermi level with intrinsic magnetism. The strong coupling between magnetism and spin–orbit coupling induces intrinsic valley polarization. Using Kinetically Limited Minimization, an unconstrained crystal structure prediction algorithm, and prototype sampling based on first-principles calculations, we have discovered new Ferrovalley materials, rare-earth iodides RI₂, where R is a rare-earth element belonging to Sc, Y, or La-Lu, and I is Iodine. The rare-earth iodides are layered and demonstrate either 2H, 1T, or 1T_d phase as the ground state in bulk, analogous to transition metal dichalcogenides (TMDCs). The calculated exfoliation energy of monolayers (MLs) is comparable to that of graphene and TMDCs, suggesting possible experimental synthesis. The MLs in the 2H phase exhibit ferromagnetism due to unpaired electrons in d and f orbitals. Throughout the rare-earth series, d bands have valley polarization at K and $$\overline{K}$$ points in the Brillouin zone in the vicinity of the Fermi level. Large intrinsic valley polarization in the range of 15–143 meV without external stimuli is observed in these Ferrovalley materials, which can be enhanced further by applying an in-plane bi-axial strain. These valleys can selectively be probed and manipulated for information storage and processing, potentially offering superior performance beyond conventional electronics and spintronics. Here we further show that the 2H ferromagnetic phase of RI₂ MLs possesses non-zero Berry curvature and exhibits anomalous valley Hall effect with considerable anomalous Hall conductivity. Our work will incite exploratory synthesis of the predicted Ferrovalley materials and their application in valleytronics and beyond.

• Research Organization: National Renewable Energy Laboratory (NREL), Golden, CO (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES); Khalifa University of Science and Technology
• Grant/Contract Number: AC36-08GO28308; FSU-2020-11/2020
• OSTI ID: 1922633
• Report Number(s): NREL/JA-5K00-85182; MainId:85955; UUID:6449d426-aa41-49f5-81a1-557f04fecd96; MainAdminID:68603
• Journal Information: 2D Materials, Vol. 10, Issue 1; Related Information: 83386; ISSN 2053-1583
• Publisher: IOP Publishing
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
97 MATHEMATICS AND COMPUTING
2D materials
materials discovery
valleytronics