Effects of strain on the electronic structure, superconductivity, and nematicity in FeSe studied by angle-resolved photoemission spectroscopy

Abstract

One of central issues in iron-based superconductors is the role of structural change to the superconducting transition temperature (Tc). It was found in FeSe that the lattice strain leads to a drastic increase in Tc, accompanied by suppression of nematic order. By angle-resolved photoemission spectroscopy on tensile-or compressive-strained and strain-free FeSe, we experimentally show that the in-plane strain causes a marked change in the energy overlap (∆E h−e ) between the hole and electron pockets in the normal state. The change in ∆E h−e modifies the Fermi-surface volume, leading to a change in Tc. Furthermore, the strength of nematicity is also found to be characterized by ∆E h−e . These results suggest that the key to understanding the phase diagram is the fermiology and interactions linked to the semimetallic band overlap.

Universal scaling behavior of the upper critical field in strained FeSe0.7Te0.3 thin films

“…The films have different a-axis lengths due to different in-plane compressive strain resulting mainly from the large thermal misfit between the substrates and the FeSe 1−x Te x layer [21,22,[28][29][30][31][32]. It is apparent that the superconducting transition temperature T c decreases linearly with increasing a-axis lattice parameter for the FeSe 0.7 Te 0.3 films, which is consistent with reports of other groups [33][34][35]. A linear dependence of T c on the crystallographic a-axis was also found for Ba(Fe,Co) 2 As 2 thin films [28].…”

“…CC-BY 4.0 https://creativecommons.org/licenses/by/4.0/. chemical potential resulting in a considerable change of the small ε F value or even the appearance of a Lifshitz transition [34]. These changes of the electronic structure can affect T c as was demonstrated before for the 122 system [30].…”

Investigation of Transport Properties for FeSe1−xTex Thin Films under Magnetic Fields

“…However, the Dirac points of FeSe films on CaF 2 are at some distance from E F , compared with that for FeSe single crystals. 33) The difference in the band structures may lead to the difference in R H between single crystals and films on CaF 2 at low temperatures.…”

Stabilization and heteroepitaxial growth of metastable tetragonal FeS thin films by pulsed laser deposition

“…Here it should be noted that the structure of all the t-FeS films obtained was expanded along the c-axis and contracted along the a-axis compared with the corresponding values for a t-FeS single crystal. In a t-FeSe thin film, in-plane lattice variation should affect superconductivity more strongly than out-of-plane lattice variation [35]. Moreover, superconductivity in t-FeS bulk disappears by applying external pressure [36].…”