High-order replica bands in monolayer FeSe/SrTiO3 revealed by polarization-dependent photoemission spectroscopy

Chong Liu,Frederick J Walker,Fengmiao Li,Pinder Dosanjh,George A Sawatzky,Giorgio Levy,Sergey Zhdanovich,Ryan L Roemer,Andrea Damascelli,Charles H Ahn,Michael Schneider,Sangjae Lee,Juan Jiang,Doug Wong,Ryan P Day,Ke Zou,Tor M Pedersen,Sergey Gorovikov

doi:10.1038/s41467-021-24783-5

Abstract

The mechanism of the enhanced superconductivity in monolayer FeSe/SrTiO3 has been enthusiastically studied and debated over the past decade. One specific observation has been taken to be of central importance: the replica bands in the photoemission spectrum. Although suggestive of electron-phonon interaction in the material, the essence of these spectroscopic features remains highly controversial. In this work, we conduct angle-resolved photoemission spectroscopy measurements on monolayer FeSe/SrTiO3 using linearly polarized photons. This configuration enables unambiguous characterization of the valence electronic structure with a suppression of the spectral background. We consistently observe high-order replica bands derived from various Fe 3d bands, similar to those observed on bare SrTiO3. The intensity of the replica bands is unexpectedly high and different between dxy and dyz bands. Our results provide new insights on the electronic structure of this high-temperature superconductor and the physical origin of the photoemission replica bands.

Highlights

IntroductionFit peaks βδ Cumulated fit 0 −0.6 βδ method such as the spline that cannot yield consistent results measurement parameters makes it arduous to determine the between different measurements appears to be less suitable for intrinsic difference of replica band intensity for different Ephoton quantitative and delicate analysis
Fit peaks βδ Cumulated fit 0 −0.6 βδ method such as the spline that cannot yield consistent results measurement parameters makes it arduous to determine the between different measurements appears to be less suitable for intrinsic difference of replica band intensity for different Ephoton quantitative and delicate analysis. or θ.Photon energy-/emission angle-dependent angle-resolved photoemission spectroscopy (ARPES) results
The doping level determined from the size of the electron pocket is ~0.11 electrons per Fe, while the superconducting gap is ~15.0 meV extracted from the energy distribution curve (EDC) at the Fermi momentum (Supplementary Fig. 2a), indicating high sample quality

Summary

Introduction

Fit peaks βδ Cumulated fit 0 −0.6 βδ method such as the spline that cannot yield consistent results measurement parameters makes it arduous to determine the between different measurements appears to be less suitable for intrinsic difference of replica band intensity for different Ephoton quantitative and delicate analysis. Ke is dependent on incident photon energy Ephoton, and θ is dependent on both ke and the measured in-plane momentum kk in the reciprocal space. Photon polarization has suppressed a great portion of background observed in previous experiments, we found that a complicated Ephoton-dependent (Fig. 5d) and θ-dependent (Fig. 5e–h) background persists, due to the neighboring d bands, the inelastic scattering of photoelectrons, or Debye–Waller effects on photoemission matrix elements[38].

Methods

Results

Conclusion