Understanding the flat band in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mn>1</mml:mn><mml:mi>T</mml:mi><mml:mtext>−</mml:mtext><mml:msub><mml:mi>TaS</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math> using a rotated basis

Abstract

The emergence of electronic flat bands in moir\'e superlattices has attracted much attention. Actually, a charge density wave (CDW) superlattice can play the same role, and 1$T$-TaS${}_{2}$ represents an example. Although there has been a lively debate on the strongly correlated physics in 1$T$-TaS${}_{2}$, a transparent theoretical understanding of the starting point -- the single-electron band dispersion -- is still elusive. This Letter shows how to understand the flat band in this compound with a rotated basis, a simple trigonometric function, and a 3$\ifmmode\times\else\texttimes\fi{}$3 matrix.

Topics & Concepts