Pseudogap in a crystalline insulator doped by disordered metals

Abstract

A key to understand how electrons behave in crystalline solids is the band structure that connects the energy of electron waves to their wavenumber (k). Even in the phase of matter with only short-range order (liquid or amorphous solid), the coherent part of electron waves still possesses a band structure. Theoretical models for the band structure of liquid metals were formulated more than 5 decades ago, but thus far, bandstructure renormalization and pseudogap induced by resonance scattering have remained unobserved. Here, we report the observation of this unusual band structure at the interface of a crystalline insulator (black phosphorus) and disordered dopants (alkali metals). We find that a conventional parabolic band structure of free electrons bends back towards zero k with the pseudogap of 30-240 meV from the Fermi level. This is k renormalization caused by resonance scattering that leads to the formation of quasi-bound states in the scattering potential of alkali-metal ions. The depth of this potential tuned by different kinds of alkali metal (Na, K, Rb, and Cs) allows to classify the pseudogap of p-wave and d-wave resonance. Our results may provide a clue to the puzzling spectrum of various crystalline insulators doped by disordered dopants, such as the waterfall dispersion in cuprates.

References in corpus (15)

• Scanning tunneling spectroscopy of high-temperature superconductors
• Observation of tunable bandgap and anisotropic Dirac semimetal state in black phosphorus
• Observation of a $d$-wave gap in electron-doped Sr${}_2$IrO${}_4$
• A universal high energy anomaly in angle resolved photoemission spectra of high temperature superconductors - possible evidence of spinon and holon branches
• Emergence of Two-Dimensional Massless Dirac Fermions, Chiral Pseudospins, and Berry's Phase in Potassium Doped Few-Layer Black Phosphorus
• "Waterfalls" phenomenon in superconducting cuprates
• "Waterfalls" in cuprates
• Momentum and excitation energy dependence of the "waterfalls" in cuprates
• Pseudogap of metallic layered nickelate R2-xSrxNiO4 (R=Nd, Eu) crystals measured using angle-resolved photoemission spectroscopy
• Electronic Structure of Electron-doped Sm1.86Ce0.14CuO4: Strong `Pseudo-Gap' Effects, Nodeless Gap and Signatures of Short Range Order
• Anisotropic two-dimensional screening at the surface of black phosphorus
• Evolution of charge order topology across a magnetic phase transition in cuprate superconductors
• Radial Band Structure of Electrons in Liquid Metals
• Isotropic charge screening of the anisotropic black phosphorus revealed by potassium adatoms
• Abrupt Onset of Second Energy Gap at Superconducting Transition of Underdoped Bi2212

Cited by in corpus (7)

• Angle-resolved photoemission spectroscopy
• Observation of spin-momentum locked surface states in amorphous Bi${}_2$Se${}_3$
• Evolution of the electronic structure of ultrathin MnBi2Te4 Films
• Spontaneous gap opening and potential excitonic states in an ideal Dirac semimetal Ta${}_2$Pd${}_3$Te${}_5$
• Establishing Coherent Momentum-Space Electronic States in Locally Ordered Materials
• Electronic rotons and Wigner crystallites in a two-dimensional dipole liquid
• Mesoscale variations of chemical and electronic landscape on the surface of Weyl semimetal Co${}_3$Sn${}_2$S${}_2$ visualized by ARPES and XPS