Electric Polarization in Magnetic Topological Nodal Semimetal Thin Films

Yuya Ominato,Ai Yamakage,Kentaro Nomura

doi:10.3390/condmat3040043

Yuya Ominato, Ai Yamakage + Show 1 more

Open Access

https://doi.org/10.3390/condmat3040043

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Abstract

We theoretically study the electric polarization in magnetic topological nodal semimetal thin films. In magnetically doped topological insulators, topological nodal semimetal phases emerge once the exchange coupling overcomes the band gap. Changing the magnetization direction, nodal structure is modulated and the system becomes topological nodal point or line semimetals. We find that nodal line semimetals are characterized by non-linear electric polarization, which is not observed in nodal point semimetals. The non-linear response originates from the existence of the surface states. Screening effect is self consistently included within a mean field approximation and the non-linear electric polarization is observed even in the presence of screening effect.

Highlights

Topological semimetals are characterized by topological numbers and topological responses [1,2,3,4]
We find that nodal line semimetals exhibit non-linear electric polarization, which originates from the existence of the surface states
We found that the system becomes topological nodal semimetal phases when the exchange coupling exceeds the band gap and the topological property of the band structure is modulated by changing the magnetization direction

Summary

Introduction

Topological semimetals are characterized by topological numbers and topological responses [1,2,3,4]. We theoretically study electric polarization in magnetic topological nodal semimetal thin films. The topological property of the band structure depends on the direction of the magnetization and the system becomes the nodal point and line semimetals by changing the direction of the magnetization [2,21,22]. We numerically calculate the band structure of the topological semimetal thin films in the presence of the external potential. The nodal line semimetal phase is characterized by the non-linear electric polarization.

Model Hamiltonian

Electric Polarization Induced by the Screened Potential

Numerical Results

Conclusions