Interfacial effects on the spin density wave in FeSe/SrTiO3thin films

Abstract

Recently, the signs of both superconducting transition temperature (T c ) beyond 60 K and spin density wave (SDW) have been observed in FeSe thin film on SrTiO 3 (STO) substrate, which suggests a strong interplay between superconductivity and magnetism. With the first-principles calculations, we find that the substrate-induced tensile strain tends to stabilize the SDW state in FeSe thin film by enhancing of the next-nearest-neighbor superexchange antiferromagnetic interaction bridged through Se atoms. On the other hand, we find that when there are oxygen vacancies in the substrate, the significant charge transfer from the substrate to the first FeSe layer would suppress the magnetic order there, and thus the high-temperature superconductivity could occur.In addition, the stability of the SDW is lowered when FeSe is on a defect-free STO substrate due to the redistribution of charges among the Fe 3d-orbitals. Our results provide a comprehensive microscopic explanation for the recent experimental findings, and build a foundation for the further exploration of the superconductivity and magnetism in this novel superconducting interface.

Dual role of Fe dopants in enhancing stability and charge transfer in(Li0.8Fe0.2)OHFeSesuperconductors

“…3 [9]. We note that the computed J 11 and J 12 in FeSe are quite close to previous results [12,29]. The order of the coupling strength is: (Fig.…”

“…We first perform lattice-constant relaxation of (Li 0.8 Fe 0.2 )OHFeSe with different functionals and van der Waals (vdW) approaches, in order to choose the proper theoretical framework that can describe the systems under investigation here [9]. In constructing the supercells, we followed two considerations: (1) (Li 0.8 Fe 0.2 )OH layers have an occupation of Li/Fe with a ratio of ∼4 [1], and thus the smallest cell is √ 5 × √ 5; (2) as discussed explicitly below, the ground-state magnetic order is found to be collinear AFM for FeSe, consistent with several previous studies of the FeSe/SrTiO 3 (FeSe/STO) system [10][11][12] The optimized lattice parameters are shown in Table I, calculated from the energy dependence on the lattice constants. The magnetic spin texture was simultaneously optimized, and the ground-state magnetism will be discussed below in Figure 3.…”

Tuning the band structure and superconductivity in single-layer FeSe by interface engineering

“…Particularly, the interfacial tensile strain has been proposed to be a critical factor 6 that normally would significantly enhance the antiferromagnetic superexchange interactions across the Fe-SeFe 8 . However, with the lattice expansion by 5.5% in FeSe BU compared with FeSe BR , T g is enhanced by only 5 K (Fig.…”

“…A burst of researches have been conducted recently on FeSe S , suggesting that the high T c might originate from epitaxial strain, interfacial electron-phonon coupling and/or charge transfer [6][7][8][9][10] . Here we directly manipulate these interfacial factors by heterostructure design.…”

Electronic evidence of an insulator–superconductor crossover in single-layer FeSe/SrTiO 3 films

“…The latest discovery of possible high-temperature superconductivity in the single-layer FeSe films grown on a SrTiO 3 substrate has attracted much attention both experimentally (19)(20)(21)(22)(23)(24)(25)(26)(27) and theoretically (28)(29)(30)(31)(32). The reduced dimensionality with enhanced interfacial effect makes this system distinct from its bulk counterpart.…”