Designing flat bands, localized and itinerant states in TaS2 trilayer heterostructures

Hyeonhu Bae; Roser Valentí; Igor I. Mazin; Binghai Yan

doi:10.1038/s41535-025-00812-0

Designing flat bands, localized and itinerant states in TaS₂ trilayer heterostructures

Hyeonhu Bae^*, Roser Valentí^*, Igor I. Mazin^*, Binghai Yan^*

^*Corresponding author for this work

Department of Condensed Matter Physics

Research output: Contribution to journal › Article › peer-review

1 Citation (Scopus)

Abstract

Stacking and twisting van der Waals materials provides a powerful tool to engineer quantum matter. For instance, 1T-TaS₂ monolayers are Mott insulators, whereas layered 1H-TaS₂ is metallic and superconducting; thus, the T/H bilayer, where heavy fermions and unconventional superconducting phases are expected from localized spins (1T) coexisting with itinerant electrons (1H), has been intensively studied. However, recent studies revealed significant charge transfer that questions this scenario. Here, we propose a T/T/H trilayer heterostructure where the T/T bilayer is a flat-dispersion band insulator with localized electrons, whereas the 1H layer remains metallic with a weak spin polarization. Varying the T/T stacking configuration tunes the flat-band filling, enabling a crossover from a doped-Mott regime to a Kondo-like state. Such a trilayer heterostructure provides, therefore, a rich novel platform to study strong correlation phenomena and unconventional superconductivity.

Original language	English
Article number	92
Journal	npj Quantum Materials
Volume	10
DOIs	https://doi.org/10.1038/s41535-025-00812-0
Publication status	Published Online - 19 Aug 2025

Funding

B.Y. acknowledged the financial support by the Israel Science Foundation (ISF: 2932/21 and 2974/23), German Research Foundation (DFG, CRC-183, A02), and by a research grant from the Estate of Gerald Alexander. I.I.M. was supported by the Office of Naval Research through the grant N00014-23-1-2480. R.V. acknowledges support by the Deutsche Forschungsgemeinschaft (DFG) through QUAST-FOR5249 —449872909 (Project TP4) and Project No. VA117/23-1—509751747.

All Science Journal Classification (ASJC) codes

Electronic, Optical and Magnetic Materials
Condensed Matter Physics

Access to Document

10.1038/s41535-025-00812-0Licence: CC BY-NC-ND

Cite this

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title = "Designing flat bands, localized and itinerant states in TaS2 trilayer heterostructures",

abstract = "Stacking and twisting van der Waals materials provides a powerful tool to engineer quantum matter. For instance, 1T-TaS2 monolayers are Mott insulators, whereas layered 1H-TaS2 is metallic and superconducting; thus, the T/H bilayer, where heavy fermions and unconventional superconducting phases are expected from localized spins (1T) coexisting with itinerant electrons (1H), has been intensively studied. However, recent studies revealed significant charge transfer that questions this scenario. Here, we propose a T/T/H trilayer heterostructure where the T/T bilayer is a flat-dispersion band insulator with localized electrons, whereas the 1H layer remains metallic with a weak spin polarization. Varying the T/T stacking configuration tunes the flat-band filling, enabling a crossover from a doped-Mott regime to a Kondo-like state. Such a trilayer heterostructure provides, therefore, a rich novel platform to study strong correlation phenomena and unconventional superconductivity.",

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AU - Bae, Hyeonhu

AU - Valentí, Roser

AU - Mazin, Igor I.

AU - Yan, Binghai

PY - 2025/8/19

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N2 - Stacking and twisting van der Waals materials provides a powerful tool to engineer quantum matter. For instance, 1T-TaS2 monolayers are Mott insulators, whereas layered 1H-TaS2 is metallic and superconducting; thus, the T/H bilayer, where heavy fermions and unconventional superconducting phases are expected from localized spins (1T) coexisting with itinerant electrons (1H), has been intensively studied. However, recent studies revealed significant charge transfer that questions this scenario. Here, we propose a T/T/H trilayer heterostructure where the T/T bilayer is a flat-dispersion band insulator with localized electrons, whereas the 1H layer remains metallic with a weak spin polarization. Varying the T/T stacking configuration tunes the flat-band filling, enabling a crossover from a doped-Mott regime to a Kondo-like state. Such a trilayer heterostructure provides, therefore, a rich novel platform to study strong correlation phenomena and unconventional superconductivity.

AB - Stacking and twisting van der Waals materials provides a powerful tool to engineer quantum matter. For instance, 1T-TaS2 monolayers are Mott insulators, whereas layered 1H-TaS2 is metallic and superconducting; thus, the T/H bilayer, where heavy fermions and unconventional superconducting phases are expected from localized spins (1T) coexisting with itinerant electrons (1H), has been intensively studied. However, recent studies revealed significant charge transfer that questions this scenario. Here, we propose a T/T/H trilayer heterostructure where the T/T bilayer is a flat-dispersion band insulator with localized electrons, whereas the 1H layer remains metallic with a weak spin polarization. Varying the T/T stacking configuration tunes the flat-band filling, enabling a crossover from a doped-Mott regime to a Kondo-like state. Such a trilayer heterostructure provides, therefore, a rich novel platform to study strong correlation phenomena and unconventional superconductivity.

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