Two -dimensional semimetal AlSb monolayer with multiple nodal-loops and extraordinary transport properties under uniaxial strain.

Two-dimensional (2D) nodal-loop semimetal (NLSM) materials have attracted much attention for their high-speed and low-consumption transporting properties as well as their fantastic symmetry protection mechanisms. In this paper, using systematic first-principles calculations, we present an excellent NLSM candidate, a 2D AlSb monolayer, in which the conduction and valence bands cross with each other forming fascinating multiple nodal-loop (NL) states. The NLSM properties of the AlSb monolayer are protected by its glide mirror symmetry, which was confirmed using a symmetry-constrained six-band tight-binding model. The transport properties of the AlSb monolayer under in-plane uniaxial strains are also studied, based on a non-equilibrium Green's function method. It is found that both compressive and tensile strains from -10% to 10% improve the transporting properties of AlSb, and it is interesting to see that flexure configurations are energetically favored when compressive uniaxial strains are applied. Our studies not only provide a novel 2D NLSM candidate with a new symmetry protection mechanism, but also raise the novel possibility for the detection of out-of-plane flexure in 2D semimetal materials.