2025/02/24 by Nisarga Paul, Ahmed Abouelkomsan, Paul, Nisarga +5 · 3 citations
Physics and Astronomy · #Cold Atom Physics and Bose-Einstein Condensates #FOS: Physical sciences #Mesoscale and Nanoscale Physics (cond-mat.mes-hall) #Quantum optics and atomic interactions #Strongly Correlated Electrons (cond-mat.str-el) #Topological Materials and Phenomena
paper · pdf · doi:10.48550/arxiv.2502.17569
openalex publication_date 2025/02/24 · openalex created_date 2025/10/15 · openalex updated_date 2026/07/28
We show that collective excitations and optical responses of moiré fractional Chern insulators (FCIs) drastically differ from those of standard fractional quantum Hall (FQH) states in a Landau level. By constructing a variational wavefunction that incorporates the moiré lattice effect, we capture the collective modes in FCIs across a range of crystal momenta including the roton minimum. Interestingly, new collective modes -- ``fractional excitons'' -- are found in the long wavelength limit (\boldsymbolq → 0) at low energy below the excitation continuum, distinct from the FQH case. Some of these modes are optically active and manifest as sharp peaks in optical conductivity at THz frequency. We further show that intraband optical absorption and spectral weight in twisted \rm MoTe2 are highly tunable by the displacement field. Our work thus establishes optical spectroscopy as a powerful tool to illuminate the unique collective modes of moiré FCIs.