From Topological Nodal-Line Semimetal to Insulator in ABW-Ge: A New Member of the Germanium Allotrope.

Topological semimetals have attracted much attention because of their excellent properties, such as ultra-high speed, low energy consumption quantum transport, and negative reluctance. Searching materials with topological semimetallic properties has become a new research field for Group-IV materials. Herein, using first-principles calculations and tight-binding modeling, we proposed a topological nodal-line semimetal ABW-Ge when spin-orbit coupling (SOC) is ignored, which is composed of pure germanium atoms in a zeolite framework ABW.

First-Principles Study on Mechanical, Electronic, and Magnetic Properties of Room Temperature Ferromagnetic Half-Metal MnNCl Monolayer.

Two-dimensional ferromagnetic (FM) half-metals are highly desirable for the development of multifunctional spintronic nano-devices due to their 100% spin polarization and possible interesting single-spin electronic states. Herein, using first-principles calculations based on density functional theory (DFT) with the Perdew-Burke-Ernzerhof (PBE) functional, we demonstrate that the MnNCl monolayer is a promising FM half-metal for spintronics. Specifically, we systematically investigated its mechanical, magnetic, and electronic properties.

Intrinsic spin-valley-coupled Dirac state in Janus functionalized β-BiAs monolayer.

Recently, a new class of 2D Dirac materials, spin-valley-coupled Dirac semimetals (svc-DSMs), was proposed in strained SbAsX monolayers (MLs) and transition metal dichalcogenide-supported graphene. Owing to the superb properties, including Dirac spin-valley Hall effect and dissipationless transport, svc-DSMs provide an ideal platform for exploring the integration of Dirac physics, spintronics and valleytronics. However, the predicted candidate materials are all extrinsic, requiring tensile strain or proximity effect.

T-C: a low-density transparent superhard carbon allotrope assembled from C cage-like cluster.

Owing to the various ways of chemical bonding, carbon can form abundant allotropes with different frameworks, which harbor rich mechanical and electronic properties. Taking the cage-like isomer of C cluster as a building block, we design a new low-density carbon allotrope, which has tetragonal symmetry (I4/mmm) and a 56-atom unit cell, hence termed as T-C. Our first-principles calculations reveal that T-C is not only energetically, dynamically, thermally (above 1800 K) and mechanically stable, but even more stable than the experimentally synthesized C20-sc and T-carbon.

All-Silicon Topological Semimetals with Closed Nodal Line.

Because of the natural compatibility with current semiconductor industry, silicon allotropes with diverse structural and electronic properties provide promising platforms for next-generation Si-based devices. After screening 230 all-silicon crystals in the zeolite frameworks by first-principles calculations, we disclose two structurally stable Si allotropes (AHT-Si and VFI-Si) containing open channels as topological node-line semimetals with Dirac nodal points forming a nodal loop in the k = 0 plane of the Brillouin zone. Interestingly, their nodal loops protected by inversion and time-reversal symmetries are robust against SU(2) symmetry breaking because of the very weak spin-orbit coupling of Si.