Weyl Semimetallic States In Transition Metal Monochalcogenide Superlattices

In condensed matter physics research,transition metal chalcogenides as new two-dimensional materials have rich physical properties and have always been the frontier field.Connect with theoretical advancement and experimental development of topological electronic properties,many transition metal chalcogenides have been found to have exotic topological nontrivial states.In the study of topological materials,topological Weyl semimetals have been widely studied due to their novel properties such as unique transport phenomena and chiral anormal phenomena under magnetic fields.But so far,it is still a challenging work for how to obtain ideal topological Weyl semimetals in an effective route.Based on first-principles calculations,we investigate the band properties of artificially designed noncentrosymmetric transition metal monochalcogenide superlattice AX/BX(A,B=Cr,Mo,W,A≠B;X=Se,Te)and combined with the tight-binding approach of the Wannier function,we explore the topological electronic properties of these superlattice structures.In this work,we mainly consider time-reversal symmetry(TRS)MoTe/WTe and MoSe/WSe and TRS broken CrTe/WTe and CrTe/MoTe,which are the Weyl and magnetic Weyl semimetals,respectively.Additionally,CrSe/WSe and CrSe/MoSe have comparatively weaker spin-orbit coupling(SOC)among six superlattices and resulting in the lack of bands crossing when concluding SOC,then making them complementary metals with zero Weyl Points(WPs).The considered systems(MoTe/WTe,MoSe/WSe,CrTe/WTe and CrTe/MoTe)are nodal line semimetals with nodal lines on three mirror planes of the Brillouin zone of hexagonal lattice in the absence of SOC.When considering the SOC,each nodal line opens a gap except for some pairs of WPs on the k_z≠0 planes.The number of WPs is material-dependent:MoTe/WTe has 6 pairs of WPs,MoSe/WSe has 12 pairs of WPs,CrTe/WTe has 6 pairs of WPs and CrTe/MoTe has 4 pairs of WPs.We identify the termination-dependent Fermi arc connection patterns on the(001)and(00(?))surfaces for four Weyl semimetal superlattices AX/BX,and the two-dimensional band dispersion of the WPs confirms that the four structures are all of the Type-ⅡWeyl semimetals.These results provide a theoretical basis to realize the possible applications of these superlattice materials in future topological electronic devices.