# Magnetic Lifshitz transition and its consequences in multi-band iron-based superconductors

## TL;DR

This paper investigates how external magnetic fields induce Lifshitz transitions in multi-band iron-based superconductors, revealing two such transitions with implications for understanding experimental phenomena.

## Contribution

It introduces a two-band model capturing Lifshitz transitions in iron-based superconductors, explaining experimental observations in FeSe and Co-doped BaFe2As2.

## Key findings

- Two Lifshitz transitions can occur in the system.
- The first transition occurs within the superconducting phase.
- Model parameters align with experimental band structures.

## Abstract

In this paper we address Lifshitz transition induced by applied external magnetic field in a case of iron-based superconductors, in which a difference between the Fermi level and the edges of the bands is relatively small. We introduce and investigate a two-band model with intra-band pairing in the relevant parameters regime to address a generic behaviour of a system with hole-like and electron-like bands in external magnetic field. Our results show that two Lifshitz transitions can develop in analysed systems and the first one occurs in the superconducting phase and takes place at approximately constant magnetic field. The chosen sets of the model parameters can describe characteristic band structure of iron-based superconductors and thus the obtained results can explain the experimental observations in FeSe and Co-doped BaFe$_{2}$As$_{2}$ compounds.