Hybridization between magneto-roton and moiré interband excitations in twisted MoTe2 creates an optically active exciton-roton mode with a characteristic roton minimum that is absent in continuum fractional quantum Hall systems.
Theory of magnetoroton bands in moir\'e materials
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abstract
The recent realization of Hofstadter spectra and fractional Chern insulators in moir\'e materials has introduced a new ingredient, a periodic lattice potential, to the study of quantum Hall phases. While the fractionalized states in moir\'e systems are expected to be in the same universality class as their counterparts in Landau levels, the periodic potential can have qualitative and quantitative effects on physical observables. Here, we examine how the magnetoroton collective modes of fractional quantum Hall (FQH) states are altered by external periodic potentials. Employing a single-mode-approximation, we derive an effective Hamiltonian for the low-energy neutral excitations expressed in terms of three-point density correlation functions, which are computed using Monte Carlo. Our analysis is applicable to FQH states in graphene with a hexagonal boron nitride (hBN) substrate and also to fractional Chern insulator (FCI) states in twisted MoTe$_2$ bilayers. We predict experimentally testable trends in the THz absorption characteristics of FCI and FQH states and estimate the external potential strength at which a soft-mode phase transition occurs between FQH and charge density wave states.
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Numerical calculations reveal a chiral p-wave roton mode at finite momentum and a d-wave nematic mode at zero momentum in the SU(2) symmetric chiral spin liquid phase of the J1-J2-Jχ model.
Tuning reciprocal-lattice Fourier components of density modulations allows arbitrary enhancement of the FCI gap within projected flat-band theory and rescales the full low-energy spectrum to match Landau-level FQHS.
citing papers explorer
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Exciton-roton mode in moir\'e fractional Chern insulators
Hybridization between magneto-roton and moiré interband excitations in twisted MoTe2 creates an optically active exciton-roton mode with a characteristic roton minimum that is absent in continuum fractional quantum Hall systems.
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Collective excitations in chiral spin liquid: chiral roton and long-wavelength nematic mode
Numerical calculations reveal a chiral p-wave roton mode at finite momentum and a d-wave nematic mode at zero momentum in the SU(2) symmetric chiral spin liquid phase of the J1-J2-Jχ model.
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How Similar Can Fractional Chern Insulators Be to Fractional Quantum Hall States? Moir\'e-Enhanced Gaps and Excitation-Spectrum Correspondence
Tuning reciprocal-lattice Fourier components of density modulations allows arbitrary enhancement of the FCI gap within projected flat-band theory and rescales the full low-energy spectrum to match Landau-level FQHS.