Direct evidence of a charge depletion region at the interface of Van der Waals monolayers and dielectric oxides: The case of superconducting FeSe/STO

Abstract

The discovery of two dimensional Van der Waals materials has opened up several possibilities for designing novel devices. Yet a more promising way of designing exotic heterostutures with improved physical properties is to grow a monolayer of these materials on a substrate. For example, in the field of superconductivity it has been demonstrated that the superconducting transition temperature of a monolayer of FeSe grown on some oxide substrates e.g., strontium titanate (STO) is by far higher than its bulk counterpart. Although the system has been considered as a model system for understanding the phenomenon of high-temperature superconductivity, the physical mechanism responsible for this high transition temperature is still highly under debate. Here using momentum and energy resolved high-resolution electron energy-loss spectroscopy we probe the dynamic charge response of the FeSe/STO(001) system and demonstrate that the frequency- and momentum-dependent dynamic charge response is not compatible with a simple film/substrate model. Our analysis reveals the existence of a depletion region at the interface between this Van der Waals monolayer and the substrate. The presence of the depletion layer, accompanied with a considerably large charge transfer from STO into the FeSe monolayer, leads to a strong renormalization of the STO energy bands and a substantial band bending at the interface. Our results shed light on the electronic complexities of the FeSe/oxide interfaces and pave the way of designing novel low-dimensional high-temperature superconductors through interface engineering. We anticipate that the observed phenomenon is rather general and can take place in many two dimensional Van der Waals monolayers brought in contact with dielectric oxides or semiconducting substrates.

arXiv comment12 pages, 3 figures

References in corpus (51)

• Van der Waals heterostructures
• 2D materials and van der Waals heterostructures
• Interface induced high temperature superconductivity in single unit-cell FeSe films on SrTiO3
• Superconductivity in single-layer films of FeSe with a transition temperature above 100 K
• Phase Diagram and High Temperature Superconductivity at 65 K in Tuning Carrier Concentration of Single-Layer FeSe Films
• Near-degeneracy of several pairing channels in multiorbital models for the Fe-pnictides
• Interfacial mode coupling as the origin of the enhancement of Tc in FeSe films on SrTiO3
• Interface-induced superconductivity and strain-dependent spin density wave in FeSe/SrTiO3 thin films
• Electronic Origin of High Temperature Superconductivity in Single-Layer FeSe Superconductor
• Heavily electron-doped electronic structure and isotropic superconducting gap in AxFe2Se2 (A=K,Cs)
• Evolution of high-temperature superconductivity from low-Tc phase tuned by carrier concentration in FeSe thin flakes
• Phonon-enhanced superconductivity at the FeSe/SrTiO3 interface
• Strong Interplay between Stripe Spin Fluctuations, Nematicity and Superconductivity in FeSe
• Critical role of substrate in the high temperature superconductivity of single layer FeSe on Nb:BaTiO${}_3$
• First-principles modeling of electrostatically doped perovskite systems
• Universal Substrate Effect on the Superconductivity of FeSe Monolayer Films
• Nanoscale phase separation of antiferromagnetic order and superconductivity in K${}_{0.75}$Fe${}_{1.75}$Se${}_2$
• Origin of charge transfer and enhanced electron-phonon coupling in single unit-cell FeSe films on SrTiO3
• The Role of SrTiO3 Phonon Penetrating into thin FeSe Films in the Enhancement of Superconductivity
• Enhanced superconductivity accompanying a Lifshitz transition in electron-doped FeSe monolayer
• Anisotropic spin fluctuations in detwinned FeSe
• Ubiquitous strong electron phonon coupling at the interface of FeSe/SrTiO3
• Dynamic interfacial polaron enhanced superconductivity of FeSe/SrTiO3
• Measurement of the dynamic charge response of materials using low-energy, momentum-resolved electron energy-loss spectroscopy (M-EELS)
• High Tc via spin fluctuations from incipient bands: application to monolayers and intercalates of FeSe
• Neutron scattering Measurements of the phonon density of states of FeSe${}_{1-x}$ superconductors
• Interplay between lattice and spin states degree of freedom in the FeSe superconductor: dynamic spin state instabilities
• Electron phonon coupling versus photoelectron energy loss at the origin of replica bands in photoemission of FeSe on SrTiO${}_3$
• 20 K superconductivity in heavily electron doped surface layer of FeSe bulk crystal
• Crossover of Charge Fluctuations across the Strange Metal Phase Diagram
• Evolution of spin excitations from bulk to monolayer FeSe
• Ab initio Study of Cross-Interface Electron-Phonon Couplings in FeSe Thin Films on SrTiO${}_3$ and BaTiO${}_3$
• Charge transfer and electron-phonon coupling in monolayer FeSe on Nb doped SrTiO${}_3$
• Accumulation, inversion, and depletion layers in SrTiO${}_3$
• Dipolar phonons and electronic screening in monolayer FeSe on SrTiO${}_3$
• Heavy non-degenerate electrons in doped strontium titanate
• Lattice Dynamics of Ultrathin FeSe Films on SrTiO3
• Detection of bosonic mode as a signature of magnetic excitation in one unit cell FeSe on SrTiO3
• Eliashberg theory for spin-fluctuations mediated superconductivity -- Application to bulk and monolayer FeSe
• The influence of spin-phonon coupling on antiferromagnetic spin fluctuations in FeSe under pressure: the First-principles calculations with van der Waals corrections
• Universal Structural Influence on the 2D Electron Gas at SrTiO${}_3$ Surfaces
• Interfacial Electron-Phonon Coupling Constants Extracted from Intrinsic Replica Bands in Monolayer FeSe/SrTiO${}_3$
• Unconventional pairing in single FeSe layers
• Dichotomy of the Photo Induced 2-Dimensional Electron Gas on SrTiO${}_3$ Surface Terminations
• Multichannel superconductivity of monolayer FeSe on SrTiO${}_3$: Interplay of spin fluctuations and electron-phonon interaction
• Interplay between band structure and Hund's correlation to increase T${}_c$ in FeSe
• Direct probing of a large spin-orbit coupling in the FeSe superconducting monolayer on STO: Evidence for nontrivial topological states
• On the phonon dispersion relation of single-crystalline $\beta$--FeSe
• Enhanced superconductivity in FeSe/SrTiO${}_3$ from the combination of forward scattering phonons and spin fluctuations
• Theory of spin-polarized high-resolution electron energy loss spectroscopy from nonmagnetic surfaces with a large spin-orbit coupling
• Modulation doping of the FeSe monolayer on SrTiO${}_3$

Cited by in corpus (2)

• Ubiquity of the spin-orbit induced magnon nonreciprocity in ultrathin ferromagnets
• Temperature evolution of the Fermi surface of the FeSe monolayer on SrTiO${}_3$