A Study Of The Photoconductive Properties Of Triple Fermions

After the concept of topology was introduced into physics,the classification of materials became more and more extensive.Topological materials such as topological semimetal and topological insulators have ushered in a hot wave of research.Physicists have theoretically pre-dicted many topological materials,but not many have been experimentally confirmed,so there is still a lot of room for exploration.With more and more people studying topological materials,there are more and more kinds of topological materials,such as two-dimensional topologi-cal insulators,three-dimensional topological insulators,Dirac semimetals,Weyl semimetals,nodal-line semimetals,triple fermion semimetals and so on.Exploring the properties of these materials can explore some strange topological properties theoretically or experimentally.We hope that these exotic properties will lead to practical applications.There are many kinds of topological materials.This paper briefly describes how topological materials are classified and the different properties of topological materials under different classification.We will focus on the analysis of the optical conductivity properties of triple fermions semimetals.The study of electronic properties of solid materials generally starts from the system Hamiltonian,which generally has two forms:lattice model and continuous model.The tight binding model is a common lattice model.Generally,the lattice model can be obtained by expanding the continuous model at a point near Brillouin zone.We use a Hamiltonian model conforming to triple fermions such as H=d·?,which is represented by a matrix,and its band structure and conductivity can be obtained by finding the eigenvalue or Green's function of the matrix.It is found that the model has three bands,one of which is flat band,and a triple degeneracy point at the zero band.The existence of flat bands results in optical conductivity related to transitions between the zero band and the conduction band,reflecting the band structure of conducting electrons that is different from other materials.Based on the optical conductivity formula derived from the Kubo formula,the optical conductivity characteristics of different monopole charges under continuous model and lattice model are calculated by theoretical calculation and numerical simulation respectively,and some special results are found.We hope that our research can provide a theoretical reference for practical materials.In the continuous model,it is found by theoretical analysis that the diagonal conductivity is highly anisotropic,and the value of non-diagonal conductivity is zero.The dependence of?on the interband conductivity of different monopole charges in the low energy model is different.The real part of?_xxbetween bands is always linearly dependent on the optical fre-quency,whereas the real part of?_zzis proportional to?^2/n-1(n is a monopole),which may be a unique fingerprint of the monopole charge.For the lattice model,it is found that the anomalous hall conductivity still exists through numerical simulation,and the simulation results show that the symbol changes.For the extreme points appearing in the lattice model,the characteristic frequencies of the node structure are strictly calculated.The work in this paper will help us to build a basic picture of the linear optical response of topological triple fermions semimetals and help to identify them from other materials.It is hoped that there will be more and more topological materials and they will bring convenience to human beings in practical application.