Abstract

We theoretically study the lattice distortion induced first and second order topological phase transition in rectangular FeSe$_{x}$Te$_{1-x}$ monolayer. When compressing the lattice constant in one direction, our first principles calculation shows that the FeSe$_x$Te$_{1-x}$ undergoes a band inversion at $\Gamma$ point in a wide dopping range, say $x\in(0.0,0.7)$, which ensures coexistence of the topological band state and the high-T$_{\rm c}$ superconductivity. This unidirectional pressure also leads to the C$_4$ symmetry breaking which is necessary for the monolayer FeSe$_x$Te$_{1-x}$ to support Majorana corner states in the either presence or absence of time-reversal symmetry. Particularly, we use $k\cdot p$ methods to fit the band structure from the first principles calculation and found that the edge states along the $(100)$ and $(010)$ directions have different Dirac energy due to C$_4$ symmetry breaking. This is essential to obtain Majorana corner states in D class without concerning the details of the superconducting pairing symmetries and Zeeman form, which can potentially bring advantages in the experimental implementation.

Highlights

  • The hybrid of superconductivity and topological band structure can provide an experimentally accessible platform to obtain the Majorana zero modes (MZMs) [1]

  • As the FeSexTe1−x/SrTiO3(110) monolayer has been experimentally observed to be a high-Tc superconductor [49], we further study its topological property in the presence of the superconductivity

  • As this is essential for realizing the second-order topological phase transition, we construct the edge theory to study the effect of the lattice distortion on the edge states

Read more

Summary

INTRODUCTION

The hybrid of superconductivity and topological band structure can provide an experimentally accessible platform to obtain the Majorana zero modes (MZMs) [1]. The implementation of the high-order topological superconductors in iron-based superconductors can provide a promising approach to achieve the MZMs in one large-gap superconductor and avoiding complex heterostructure. Our firstprinciples calculations show that when the in-plane lattice constant in one direction is reduced, the electronic band structure of the monolayer FeSexTe1−x can achieve a strong TI phase within a wide range of composition x values. This results in the first-order topological phase transition (TPT) of the inverted band structures with one pair of helical edge states at each edge. IV, we discuss the experimental reality for our model and give the conclusion

The first-principles calculations of the band structure
The model Hamiltonian and the edge theory
LATTICE DISTORTION INDUCED SECOND-ORDER TPT
High-order TSC in DIII class
High-order TSC in D class
DISCUSSION AND CONCLUSION
Full Text
Published version (Free)

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call