The spin-wave energy spectrum and transition temperature of the two-dimensional VSe2-like: a retarded Green's function method study

Based on the recent discovery of intrinsic magnetism in monolayer films VSe2, we have constructed a two-dimensional (2D) Heisenberg model incorporating the 1T and 2H structures. These configurations consist of three layers: the upper and lower surface layers and a middle layer. Using the retarded Green's function method, we investigate the spin-wave energy spectrum, spin-wave density of states, and transition temperature of the system. It is found that in the 2H structure, the spin-wave energy spectrum of the system exhibits three direct energy gaps, with one branch being independent of the wave vector. Further analysis shows that at this constant energy, a particular surface state emerges in the 2H structure. In contrast, the spin-wave energy spectrum in the 1T structure features only two energy gaps-one direct energy gap1 and one indirect energy gap3-without forming a unique surface state. Single-ion anisotropy and interlayer interactions between the upper and lower surface layers influence the energy gaps in the spin-wave energy spectrum and the system's transition temperature. This theoretical work sheds light on forming particular surface states in monolayer 2H structure magnetic materials. It provides crucial theoretical support for designing and fabricating next-generation low-dimensional magnetic random-access memory.