New classes of two-dimensional (2D) materials beyond graphene, including layered and non-layered, and their heterostructures, are currently attracting increasing interest due to their promising applications in nanoelectronics, optoelectronics and clean energy, where thermal transport is a fundamental physical parameter. In this paper, we systematically investigated the phonon transport properties of the 2D orthorhombic group IV–VI compounds of GeS, GeSe, SnS and SnSe by solving the Boltzmann transport equation (BTE) based on first-principles calculations. Despite their similar puckered (hinge-like) structure along the armchair direction as phosphorene, the four monolayer compounds possess diverse anisotropic properties in many aspects, such as phonon group velocity, Young's modulus and lattice thermal conductivity (κ), etc. Especially, the κ along the zigzag and armchair directions of monolayer GeS shows the strongest anisotropy while monolayer SnS and SnSe show almost isotropy in phonon transport. The origin of the diverse anisotropy is fully studied and the underlying mechanism is discussed in details. With limited size, the κ could be effectively lowered, and the anisotropy could be effectively modulated by nanostructuring, which would extend the applications to nanoscale thermoelectrics and thermal management. Our study offers fundamental understanding of the anisotropic phonon transport properties of 2D materials, and would be of significance for further study, modulation and applications in emerging technologies.

A new family of topological magnon insulators with intrinsic gap-tunability is realized in 2D van der Waals ferromagnets.

By means of extensive ab initio calculations, a new two-dimensional (2D) atomic material tin selenide monolayer (coined as tinselenidene) is predicted to be a semiconductor with an indirect gap (~1.45 eV) and a high hole mobility (of order 10000 cm²V⁻¹S⁻¹) and will bear an indirect-direct gap transition under a rather low strain (<0.5 GPa). Tinselenidene has a very small Young’s modulus (20–40 GPa) and an ultralow lattice thermal conductivity (<3 Wm⁻¹K⁻¹ at 300 K), making it probably the most flexible and most heat-insulating material in known 2D atomic materials. In addition, tinseleniden has a large negative Poisson’s ratio of −0.17, thus could act as a 2D auxetic material. With these intriguing properties, tinselenidene could have wide potential applications in thermoelectrics, nanomechanics and optoelectronics.

The thermal conductivity of monolayer CrI ₃ is enlarged more than two orders of magnitude by the spin–lattice coupling, which would be large enough for its applications in nanoelectronics and magnetic storage.

The properties of Kitaev materials are attracting ever increasing attention owing to their exotic properties. In realistic two-dimensional materials, the Kitaev interaction is often accompanied by the Dzyaloshinskii-Moriya interaction, which poses a challenge for distinguishing their magnitudes separately. In this paper, we demonstrate that it can be done by accessing magnonic transport properties. By studying honeycomb ferromagnets exhibiting Dzyaloshinskii-Moriya and Kitaev interactions simultaneously, we reveal nontrivial magnonic topological properties accompanied by intricate magnonic transport characteristics as given by thermal Hall and magnon Nernst effects. We also investigate the effect of a magnetic field, showing that it does not only break the symmetry of the system but also brings drastic modifications to magnonic topological transport properties, which serve as hallmarks of the relative strength of anisotropic exchange interactions. Based on our findings, we suggest strategies to estimate the importance of Kitaev interactions in real materials.

Carbon materials exhibit diverse mechanical properties, from hard diamond to soft graphite. However, carbon materials with high ductility are rare, because of strong covalent bonds between carbon atoms. Here, we propose that the structures of triangular lattice have higher ductility than those of hexagonal or quadrangle lattice. A two-dimensional (2D) carbon network, named a carbon Kagome lattice (CKL), is used as an example to verify the point. The carbon structure has a Kagome lattice similar to the triangular lattice. Because empirical potentials cannot well simulate mechanical properties of carbon structures with triangular carbon rings, we work out a neuroevolution potential (NEP) based on a machine learning method. Structural evolution and phase transition under strain have been studied based on the NEP. The results indicate that the ductility of 2D CKL can approach 80%, and even at a high temperature, the ductility can reach 48%. The ductile values are the highest in all 2D crystal materials except the molecular materials. The high ductility is attributed to the phase transition of 2D CKL under tensile strain. It transits to another carbon allotrope, named Carbon Ene-Yne graphyne, which can also sustain a large tensile strain. Our work not only proposes that the materials with triangular lattice have high ductile ability but also finds a 2D carbon material with the highest ductility, extending mechanical applications of materials.