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Excitonic charge density waves in moiré ladders

Paula Mellado1,*, Francisco Muñoz2, and Javiera Cabezas-Escares2

  • *Contact author: paula.mellado@uai.cl
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APS Open Sci. 1, 000003 – Published 29 April, 2026

DOI: https://doi.org/10.1103/clc3-57sk

Abstract

An incommensurate charge density wave (CDW) is a periodic modulation of charge that breaks translational symmetry incongruently with the underlying lattice. Its low-energy excitations, the phasons, are collective, gapless phase fluctuations. We study a half-filled, four-band ladder model where a shift δ=p/q between the legs leads to a supercell of q composite cells. The moiré potential narrows minibands near the Fermi level, resulting in additional peaks in the density of states, whose separation is controlled by δ. The inclusion of short-range Coulomb interactions leads to an excitonic incommensurate CDW state. We identify the oscillations in its amplitude with a gapped Higgs collective mode and a lowest-energy Goldstone mode, realized by long-lived neutral phasons whose propagation velocity is governed by the shift δ and the interleg tunneling amplitude. Our results show that even the slightest interlayer mismatches can strongly modify both charge-ordering patterns and low-energy bosonic excitations in layered materials, and suggest that the enigmatic CDW phase in the quasi-one-dimensional compound HfTe3 is excitonic in nature.

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Sliding phasons in moiré ladders

Paula Mellado, Francisco Muñoz, and Javiera Cabezas-Escares
Phys. Rev. B 113, 165152 (2026)

Article Text

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APS Open Sci. 1, 000003– Published 29 April, 2026
Vol. 1
  • Received 5 December 2025
  • Accepted 9 March 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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