Possible Excitonic Insulating Phase in Quantum-Confined Sb Nanoflakes

Zhi Li, Muhammad Nadeem, Zengji Yue, David Cortie, Michael Fuhrer, Xiaolin Wang

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In the 1960s, it was proposed that in small indirect band-gap materials, excitons can spontaneously form because the density of carriers is too low to screen the attractive Coulomb interaction between electrons and holes. The result is a novel strongly interacting insulating phase known as an excitonic insulator. Here we employ scanning tunnelling microscopy (STM) and spectroscopy (STS) to show that the enhanced Coulomb interaction in quantum-confined elemental Sb nanoflakes drives the system to the excitonic insulator state. The unique feature of the excitonic insulator, a charge density wave (CDW) without periodic lattice distortion, is directly observed. Furthermore, STS shows a gap induced by the CDW near the Fermi surface. Our observations suggest that the Sb(110) nanoflake is an excitonic insulator.

Original languageEnglish
Pages (from-to)4960-4964
Number of pages5
JournalNano Letters
Issue number8
Publication statusPublished - 14 Aug 2019


  • antimony
  • Excitonic insulating phase
  • quantum confinement
  • STM

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