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Pseudogap in a crystalline insulator doped by disordered metals

DOI: 10.1038/s41586-021-03683-0 DOI Help

Authors: Sae Hee Ryu (Yonsei University) , Minjae Huh (Yonsei University; Pohang University of Science and Technology) , Do Yun Park (Yonsei University) , Chris Jozwiak (Advanced Light Source) , Eli Rotenberg (Advanced Light Source) , Aaron Bostwick (Advanced Light Source) , Keun Su Kim (Yonsei University)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Nature , VOL 596 , PAGES 68 - 73

State: Published (Approved)
Published: August 2021
Diamond Proposal Number(s): 25869

Abstract: Key to our understanding of how electrons behave in crystalline solids is the band structure that connects the energy of electron waves to their wavenumber. Even in phases of matter with only short-range order (liquid or amorphous solid), the coherent part of electron waves still has a band structure. Theoretical models for the band structure of liquid metals were formulated more than five decades ago, but, so far, band-structure renormalization and the pseudogap induced by resonance scattering have remained unobserved. Here we report the observation of the 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 wavenumber with a pseudogap of 30–240 millielectronvolts from the Fermi level. This is wavenumber renormalization caused by resonance scattering, leading 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 disordered alkali metal (sodium, potassium, rubidium and caesium) allows the classification of 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 observed in copper oxides.

Journal Keywords: Electronic properties and materials; Superconducting properties and materials; Surfaces, interfaces and thin films; Two-dimensional materials

Subject Areas: Materials, Physics

Instruments: I05-ARPES

Other Facilities: Beamline 7.0.2 (MAESTRO) at Advanced Light Source

Added On: 10/08/2021 09:12

Discipline Tags:

Materials Science Quantum Materials Superconductors Physics Hard condensed matter - structures Surfaces interfaces and thin films

Technical Tags:

Spectroscopy Angle Resolved Photoemission Spectroscopy (ARPES)