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説明:

Transition metal dichalcogenide (TMD)-based moiré superlattices exhibit strong electron-electron correlations, thus giving rise to strongly correlated quantum phenomena such as generalized Wigner crystal states, a delicate electron crystalline phase. The evidence of Wigner crystal in TMD moire superlattice has been widely reported in various optical spectroscopy and electrical conductivity measurements, while their microscopic nature remains mostly unknown. Previous work on imaging of 2D Wigner crystal only provided limited information such as lattice structure. Important physical properties of the Wigner crystal such as its elementary excitations and the corresponding energy gaps are still unclear microscopically. Theoretical studies predict that unusual quasiparticle excitations across the correlated gap between upper and lower Hubbard bands can arise due to long-range Coulomb interactions in generalized Wigner crystal states. The microscopic probe of such quasiparticle excitations, however, is non-trivial because of the fragility and low excitation energy of the Wigner crystal. Here we describe a new scanning single-electron charging (SSEC) spectroscopy technique with nanometer spatial resolution and single-electron charge resolution that enables us to directly image electron and hole wavefunctions and to determine the thermodynamic gap of generalized Wigner crystal states in twisted WS2 moiré heterostructures. High-resolution SSEC spectroscopy was achieved by combining scanning tunneling microscopy (STM) with a monolayer graphene sensing layer, thus enabling the generation of individual electron and hole quasiparticles in generalized Wigner crystals. We show that electron and hole quasiparticles have complementary wavefunction distributions and that thermodynamic gaps of order 50meV exist for the 1/3 and 2/3 generalized Wigner crystal states.

権利情報:

• In Copyright
  This version of the article has been accepted for publication, after peer review (when applicable) and is subject to Springer Nature’s AM terms of use, but is not the Version of Record and does not reflect post-acceptance improvements, or any corrections. The Version of Record is available online at: http://dx.doi.org/10.1038/s41565-023-01594-x

キーワード: Generalized Wigner crystal, TMD moiré superlattices, SSEC spectroscopy

刊行年月日: 2024-01-29

出版者: Springer Science and Business Media LLC

掲載誌:

• Nature Nanotechnology (ISSN: 17483395) vol. 19 issue. 5 p. 618-623

研究助成金:

原稿種別: 著者最終稿 (Accepted manuscript)

MDR DOI:

公開URL: https://doi.org/10.1038/s41565-023-01594-x

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更新時刻: 2025-09-03 15:51:03 +0900

MDRでの公開時刻: 2025-09-04 08:19:22 +0900