Single-layer antiferromagnetic semiconductor CoS2 with pentagonal structure

Abstract

Structure-property relationships have always been guiding principles in discovering new materials.Here we explore the relationships to discover novel two-dimensional (2D) materials with the goal of identifying 2D magnetic semiconductors for spintronics applications. In particular, we report a density functional theory + U study of single-layer antiferromagnetic (AFM) semiconductor CoS2 with the pentagonal structure forming the so-called Cairo Tessellation. We find that this singlelayer magnet exhibits an indirect bandgap of 1.06 eV with light electron and hole effective masses of 0.03 and 0.10 m0, respectively, which may lead to high carrier mobilities. The hybrid density functional theory calculations correct the bandgap to 2.24 eV. We also compute the magnetocrystalline anisotropy energy (MAE), showing that the easy axis of the AFM ordering is out of plane with a sizable MAE of 153 µeV per Co ion. We further calculate the magnon frequencies at different spin-spiral vectors, based on which we estimate the Néel temperatures to be 20.4 and 13.3 K using the mean field and random phase approximations, respectively. We then apply biaxial strains to tune the bandgap of single-layer pentagonal CoS2. We find that the energy difference between the ferromagnetic and AFM structures strongly depends on the biaxial strain, but the ground state remains the AFM ordering. Although the low critical temperature prohibits the magnetic applications of single-layer pentagonal CoS2 at room temperature, the excellent electrical properties may find this novel single-layer semiconductor applications in optoelectronic nanodevices.

Two‐dimensional magnetic transition metal chalcogenides

“…Cobalt chalcogenides are also promising candidates for 2D magnets with multiple structural phases. CoS 2 and CoSe 2 are pyrite‐type cubic compounds, and CoS 2 is a ferromagnetic metal with T c of 124 K, whereas CoSe 2 is either a Pauli paramagnet or antiferromagnet 76,77 . Ultrathin CoX 2 crystals have been successfully fabricated by CVD, and the thickness can be controlled from a ML to tens of nanometers 78 .…”

Structures and functions of two-dimensional materials: From theoretical prediction to experimental realization

“…(c) Top (upper) and side (bottom) views of geometric structures of penta-PdS 2 and 1T-PdS 2 [48] , Copyright © 2015, Royal Society of Chemistry 提出的一种随机全局优化算法. 吉林大学马琰铭团 队 [43] [49] 、penta-SnX 2 (X=S, Se, Te)单层 [50] 、penta-CoS 2 单层 [51] 以及penta-RuS 4 单层 [52] 等的存在和性质. 2017年, Oyedele等 人 [53] 2007年, Sofo等人 [54] 将完全氢化的石墨烯命名为 石墨烷(graphane), 并基于第一性原理计算(GGA泛函) 首次预测了石墨烷的存在以及其显著增加的带隙, 基 于准粒子GW近似预测的石墨烷带隙为5.4 eV [55] .…”

Stability, electronic and magnetic properties of the penta-CoAsSe monolayer: a first-principles and Monte Carlo study

“…Very recently, a new class of 2D materials based on a pentagonal structure have been discovered, and since the design of Penta-graphene and due to the attractiveness of this specific structure, some similar 2D materials have been reported. 1,7–9 This new allotrope successfully predicted using first-principles calculations has great potential for application in many fields such as electronics, optoelectronics and catalysis. Penta-BCN displays high spontaneous polarization and prominent piezoelectricity making it a good candidate for technological applications.…”

“…Since the discovery of graphene, intensive research efforts have been devoted to developing many promising technological applications based on two-dimensional (2D) crystals, 1–4 in particular, spintronics. 5 Because of its high speed and low power consumption, spintronics is now considered one of the most exciting next-generation information technologies, which uses the spin of electrons for information storage, transport, and processing.…”