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<p>1<i>T</i>-TaS<sub>2</sub> is a non-magnetic Mott insulating transition-metal dichalcogenide with an odd number of electrons per unit cell, making it a potential spin-liquid candidate. This behavior arises from miniband reconstructions in the charge density wave state, producing a nearly flat band at half-filling. We revisit its electronic band structure using a nearest-neighbor tight-binding model, emphasizing the importance of often-neglected “spin-flip” terms in the spin-orbit coupling. By comparing with density functional theory calculations, we estimate the strength of these couplings. We also apply our theory to 1<i>T</i>-TaSe<sub>2</sub>, which is found to be a promising candidate for a topologically non-trivial flat band. Our findings have significant implications for correlated physics in the flat band, including the emergent spin-spin Hamiltonian at half-filling, identified as a <i>J</i>-<i>K</i>-<i>Γ</i>-<InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="41535_2025_747_Article_IEq1.gif" Format="GIF" Height="15" Rendition="HTML" Resolution="72" Type="Linedraw" Width="17" /> </InlineMediaObject> <EquationSource Format="TEX">\(\Gamma ^{\prime}\)</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mrow> <mi mathvariant="normal">Γ</mi> </mrow> <mrow> <mo>′</mo> </mrow> </msup> </math></EquationSource> </InlineEquation> model on a triangular lattice, and for tuning electronic properties away from half-filling.</p>

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Flat band physics in the charge-density wave state of 1T-TaS2 and 1T-TaSe2

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年3月20日

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  • Amir Dalal,
  • Jonathan Ruhman,
  • Jörn W. F. Venderbos

摘要

1T-TaS2 is a non-magnetic Mott insulating transition-metal dichalcogenide with an odd number of electrons per unit cell, making it a potential spin-liquid candidate. This behavior arises from miniband reconstructions in the charge density wave state, producing a nearly flat band at half-filling. We revisit its electronic band structure using a nearest-neighbor tight-binding model, emphasizing the importance of often-neglected “spin-flip” terms in the spin-orbit coupling. By comparing with density functional theory calculations, we estimate the strength of these couplings. We also apply our theory to 1T-TaSe2, which is found to be a promising candidate for a topologically non-trivial flat band. Our findings have significant implications for correlated physics in the flat band, including the emergent spin-spin Hamiltonian at half-filling, identified as a J-K-Γ- \(\Gamma ^{\prime}\) Γ ′ model on a triangular lattice, and for tuning electronic properties away from half-filling.