309 research outputs found
Exact Solutions of Fractional Chern Insulators: Interacting Particles in the Hofstadter Model at Finite Size
We show that all the bands of the Hofstadter model on the torus have an
exactly flat dispersion and Berry curvature when a special system size is
chosen. This result holds for any hopping and Chern number. Our analysis
therefore provides a simple rule for choosing a particularly advantageous
system size when designing a Hofstadter system whose size is controllable, like
a qubit lattice or an optical cavity array. The density operators projected
onto the flat bands obey exactly the Girvin-MacDonald-Platzman algebra, like
for Landau levels in the continuum in the case of , or obey its
straightforward generalization in the case of . This allows a mapping
between density-density interaction Hamiltonians for particles in the
Hofstatder model and in a continuum Landau level. By using the well-known
pseudopotential construction in the latter case, we obtain fractional Chern
insulator phases, the lattice counterpart of fractional quantum Hall phases,
that are exact zero-energy ground states of the Hofstadter model with certain
interactions. Finally, the addition of a harmonic trapping potential is shown
to lead to an appealingly symmetric description in which a new Hofstadter model
appears in momentum space.Comment: 15 pages, 8 figures; Published versio
Degeneracy between even- and odd-parity superconductivity in the quasi-1D Hubbard model and implications for Sr2RuO4
Based on a weak coupling calculation, we show that an accidental degeneracy
appears between even- and odd-parity superconductivity in the quasi-1D limit of
the repulsive Hubbard model on the square lattice. We propose that this effect
could be at play on the quasi-1D orbitals Ru and of Sr2RuO4,
leading to a gap of the form which
could help reconcile several experimental results.Comment: 13 pages, 2 figure
Adiabatic Continuation of Fractional Chern Insulators to Fractional Quantum Hall States
We show how the phases of interacting particles in topological flat bands, known as fractional Chern insulators, can be adiabatically connected to incompressible fractional quantum Hall liquids in the lowest Landau-level of an externally applied magnetic field. Unlike previous evidence suggesting the similarity of these systems, our approach enables a formal proof of the equality of their topological orders, and furthermore this proof robustly extends to the thermodynamic limit. We achieve this result using the hybrid Wannier orbital basis proposed by Qi [Phys. Rev. Lett. 107, 126803 (2011)] in order to construct interpolation Hamiltonians that provide continuous deformations between the two models. We illustrate the validity of our approach for the groundstate of bosons in the half filled Chern band of the Haldane model, showing that it is adiabatically connected to the nu=1/2 Laughlin state of bosons in the continuum fractional quantum Hall problem
Origin and Limit of the Recovery of Damaged Information by Time Reversal
Recently it was found that scrambled information can be partially recovered
by a time-reversed evolution, even after being damaged by an intruder. We
reconsider the origin of the information recovery, and argue that the presence
of classical chaos does not preclude it and only leads to a quantitative
reduction of the recovery ratio. We also show how decoherence (i.e.
entanglement with the intruder) limits the recovery, by proving an upper bound
on the recovery ratio in terms of the entangling power of the intruder's
action.Comment: 5 pages, 4 figures; v2: accepted version; added an appendi
Minimal model for the flat bands in copper-substituted lead phosphate apatite
Two recent preprints gave evidence that a copper-substituted lead apatite,
denoted as CuPb(PO)OH and also known as LK99, could be a
room-temperature superconductor. While other research groups have not yet
replicated the superconductivity in this material, a recent Density Functional
Theory (DFT) calculation indicated the presence of two nearly flat bands near
the Fermi level. Such flat bands are known to exhibit strongly correlated
physics, which could potentially explain the reported high-
superconductivity. In order to facilitate the theoretical study of the
intriguing physics associated with these two flat bands, we propose a minimal
tight-binding model which reproduces their main features. We also discuss
implications for superconductivity
Evidence for deconfined gauge theory at the transition between toric code and double semion
Building on quantum Monte Carlo simulations, we study the phase diagram of a
one-parameter Hamiltonian interpolating between trivial and topological Ising
paramagnets in two dimensions, which are dual to the toric code and the double
semion. We discover an intermediate phase with stripe order which spontaneously
breaks the protecting Ising symmetry. Remarkably, we find evidence that this
intervening phase is gapless due to the incommensurability of the stripe
pattern and that it is dual to a gauge theory exhibiting Cantor
deconfinement.Comment: 8 pages, 4 figures, supplemental material included (6 pages, 8
figures
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