Structural-transition-induced quasi two-dimensional Fermi surface in FeSe

TL;DR

This study reveals a quasi-two-dimensional Fermi surface in FeSe induced by structural transition, evidenced by angular-dependent magnetoresistance showing twofold symmetry and Dirac-like states with 2D characteristics.

Contribution

It provides detailed experimental evidence linking the structural transition in FeSe to the emergence of a quasi-2D Fermi surface and Dirac-cone-like states.

Findings

Pronounced twofold symmetric AMR in orthorhombic phase

Quasi-2D Fermi surface induced by structural transition

Dirac-cone-like states exhibit 2D behavior

Abstract

We report detailed study of angular-dependent magnetoresistance (AMR) with tilting angel $\theta$ from $c$-axis ranging from 0$^\circ$ to 360$^\circ$ on a high-quality FeSe single crystal. A pronounced AMR with twofold symmetry is observed, which is caused by the quasi two-dimensional (2D) Fermi surface. The pronounced AMR is observed only in the orthorhombic phase, indicating that the quasi-2D Fermi surface is induced by the structural transition. Details about the influence of the multiband effect to the AMR are also discussed. Besides, the angular response of a possible Dirac-cone-like band structure is investigated by analyzing the detailed magnetoresistance at different $\theta$. The obtained characteristic field ($B^*$) can be also roughly scaled in the 2D approximation, which indicates that the Dirac-cone-like state is also 2D in nature.