Magnetization control of the nematicity direction and nodal points in a superconducting doped topological insulator

TL;DR

This paper investigates how different magnetization directions influence nematic superconductivity and nodal point behavior in doped topological insulators, revealing magnetization-dependent spectral properties and proposing experimental tests.

Contribution

It demonstrates how magnetization orientation controls nematicity, nodal points, and surface states in doped topological insulators with superconductivity, providing new insights into their spectral characteristics.

Findings

Magnetization direction fixes nematicity orientation.

Out-of-plane magnetization favors chiral state over nematic.

Nodal points split or gap depending on magnetization orientation.

Abstract

We study the effects of magnetization on the properties of the doped topological insulator with nematic superconductivity. We found that the direction of the in-plane magnetization fixes the direction of the nematicity in the system. The chiral state is more favorable than the nematic state for large values of out-of-plane magnetization. Overall, the critical temperature of the nematic state is resilient against magnetization. We explore the spectrum of the system with the pinned direction of the nematic order parameter $\Delta_{y}$ in details. Without magnetization, there is a full gap in the spectrum. At strong enough out-of-plane $m_z$ or orthogonal in-plane $m_x$ magnetization, the spectrum is closed at the nodal points that are split by the magnetization. Flat Majorana surface states connect such split bulk nodal points. Parallel magnetization $m_y$ lifts nodal points and opens a full gap in the spectrum. We discuss relevant experiments and propose experimental verifications of our theory.