Coexistence of Replica Bands and Superconductivity in FeSe Monolayer Films

Identifying a forward-scattering superconductor through pump-probe spectroscopy

“…The normal state band structure for the forward focused case ( Fig. 2e) exhibits different behavior [12]; most notably there is a replica band below the main band, similar to the experimentally observed [10,15,31] features of the FeSe monolayer superconductors that have been explained by forward scattering from phonons. The band is flatter in the vicinity of E F due to the perfect forward scattering limit [27].…”

Multiband full-bandwidth anisotropic Eliashberg theory of interfacial electron-phonon coupling and high−Tc superconductivity in FeSeAperis1, Oppeneer2 2018Phys. Rev. B4110771View full textAdd to dashboardCite

“…Furthermore, angular resolved photoemission spectroscopy (ARPES) measurements [6] reveal an interfaceinduced electron-phonon interaction (EPI) between FeSe electrons and polar STO phonons that is strongly peaked at the q=0 phonon wavevector [6,[14][15][16][17][18]. There is growing experimental evidence for the pivotal role of such interfacial phonons in engineering high-T c heterostructures that involve FeSe [5,9,19] or even FeAs [20] monolayers.Although ab initio calculations confirm the existence of small-q phonons as a strictly interfacial phenomenon in FeSe/STO [12,[21][22][23] and indicate the importance of the coupling between substrate phonons and FeSe electrons [24], the estimated low value of the electron-phonon coupling constant (λ ≤ 0.4) has been widely considered insufficient to explain the impressive T c enhancement unless another, dominant pairing mechanism is at play [6]. On the other hand, Eliashberg calculations within a single band model suggest that interfacial phonons may lead to the high T c with a coupling of merely half of that estimated by experiments [25].…”

“…Furthermore, angular resolved photoemission spectroscopy (ARPES) measurements [6] reveal an interfaceinduced electron-phonon interaction (EPI) between FeSe electrons and polar STO phonons that is strongly peaked at the q=0 phonon wavevector [6,[14][15][16][17][18]. There is growing experimental evidence for the pivotal role of such interfacial phonons in engineering high-T c heterostructures that involve FeSe [5,9,19] or even FeAs [20] monolayers.…”

Comparative Review on Thin Film Growth of Iron-Based Superconductors

“…Nevertheless, the interface superconductivity has also been found in related materials such as FeSe on BaTiO 3 [161], Te-doped FeSe on STO [162], KFe 2 Se 2 on STO [148], FeSe on STO(110) [163,164], and FeSe on anatase TiO 2 [165]. In addition, replica bands were also observed in monolayer FeSe on anatase TiO 2 [166]. The mechanism for the enhancement of superconductivity is considered to be the same among these materials, and thus, comprehensive study including these materials will enrich understanding of the interface superconductivity in FeSe on STO.…”