Realization of continuously electron doping in bulk iron selenides and identification of a new superconducting zone

TL;DR

This study successfully synthesized a new bulk iron selenide compound with continuous electron doping, revealing a superconducting dome with a Lifshitz transition and unique electronic structure features, advancing understanding of iron-based superconductivity.

Contribution

It introduces a new bulk iron selenide family with continuous doping and maps the electronic and structural evolution across the superconducting dome.

Findings

Continuous superconducting dome with Lifshitz transition

Anion height deviates from pnictides and pressurized FeSe

Optimal superconductivity occurs with intermediate orbital correlations

Abstract

It is known that iron selenide superconductors exhibit unique characteristics distinct from iron pnicitides, especially in the electron-doped region. However, acomprehensive study of continuous carrier doping ang the corresponding crystal structures of FeSe is still lacking, mainly due to the difficulties in controlling the carrier density in bulk materials. Here, we report the successful synthesis of a new family of bulk Lix(C3H10N2)0.37FeSe, which features a continue superconducting dome harboring Lifshitz transition within the wide range of 0.06~0.68. We demonstrate that with electron-doped, the anion height of FeSe layers deviates lineraly away from the optimized values of pnictides and pressurized FeSe. This feature leads to anew superconducting zone with unique doping dependence of the electronic structures and strong orbital-selective electronic correlation. Optimal superconductivity is achieved when the Fe 3d t2g orbitals have almost the same intermediate electronic correlation strength, with moderate mass enhancement between 3~4 in the two separate superconducting zone. Our result shed light on archieving unified mechanism of superconductivity in iron-based materials.