• Accepted Paper

Wilson-loop-ideal bands and general idealization

Awwab A. Azam, Biao Lian, Shinsei Ryu, and Jiabin Yu

Phys. Rev. Lett. - Accepted 16 September, 2026

DOI: https://doi.org/10.1103/vdp3-dcht

Abstract

Quantum geometry is universally bounded from below by Wilson-loop windings. In this work, we define an isolated set of bands to be Wilson-loop-ideal, if their quantum metric saturates the Wilson-loop lower bound. The definition naturally incorporates the known Chern-ideal and Euler-ideal bands, and allows us to define other types of ideal bands, such as Kane-Mele Z2-ideal and inversion-fragile-ideal bands. In particular, we find that in the case of zero total Chern number, an isolated WL-ideal set of two bands with non-singular nonabelian Berry curvature and nontrivial normal Wilson-loop winding always admits a Chern-ideal gauge, without the need of a global good quantum number (such as spin). This enables the direct construction of new topologically ordered states, such as fractional topological insulator wavefunctions. We further propose a general framework of constructing monotonic flows that achieve Wilson-loop-ideal states starting from non-ideal bands through band mixing, where Wilson-loop-ideal states are not energy eigenstates but have smooth projectors similar to isolated bands. We apply the constructed flows to the realistic model of 3.89 twisted bilayer MoTe2, a moir'e Rashba model and another moiré time-reversal-breaking model, and numerically find Chern-ideal, Z2-ideal and inversion-fragile states, respectively, with relative error in the integrated quantum metric below 5×103. Our exact-diagonalization calculations on the numerically ideal states demonstrate the potential of our general definition of Wilson-loop-ideal bands and general procedure of constructing Wilson-loop-ideal states for future study of novel correlated physics.

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