Fermi surface topology and low-lying quasiparticle dynamics of parent Fe$_{1+x}$Te/Se Superconductor by orbital-polarization resolved ARPES

TL;DR

This study uses ARPES to explore the electronic structure of Fe$_{1+x}$Te, revealing unique Fermi surface features and magnetic properties that differ from other iron-based superconductors, suggesting a different mechanism for superconductivity.

Contribution

First ARPES investigation of Fe$_{1+x}$Te revealing its distinct Fermi surface topology and magnetic order, highlighting differences from pnictide superconductors.

Findings

Nearly electron-hole compensated Fermi pockets

Absence of spin-density-wave gap

Shadow hole pocket at X-point

Abstract

We report the first photoemission study of Fe$_{1+x}$Te - the host compound of the newly discovered iron-chalcogenide superconductors (maximum T$_c$ $\sim$ 27K). Our results reveal a pair of nearly electron-hole compensated Fermi pockets, strong Fermi velocity renormalization and an absence of a spin-density-wave gap. A shadow hole pocket is observed at the X-point of the Brillouin zone which is consistent with a long-range ordered magneto-structural groundstate. No signature of Fermi surface nesting instability associated with Q=($\pi$/2, $\pi$/2) is observed. Our results collectively reveal that the Fe$_{1+x}$Te series is dramatically different from the high T$_{c}$ pnictides and likely harbor unusual mechanism for superconductivity and magnetic order.