10 research outputs found
On the coexistence of antiferromagnetism and d + i d superconducting correlations in the graphene bilayer
We discuss t-J-U model on a honeycomb monolayer that has the same low-energy
description of the kinetic term as graphene bilayer, and in particular study
coexistence of antiferromagnetism and superconducting correlations that
originate from Cooper pairs without phase coherence. We show that the model is
relevant for the description of graphene bilayer and that the presence of the d
+ i d superconducting correlations with antiferromagnetism can lead to
quadratic dependence in small magnetic fields of the gap of the effective
monolayer consistent with the transport measurements of Velasco et al. on the
graphene bilayer.Comment: 6 pages, 1 figure, references adde
Charge fluctuations, hydrodynamics and transport in the square-lattice Hubbard model
Recent experimental results suggest that a particular hydrodynamic theory
describes charge fluctuations at long wavelengths in the square-lattice Hubbard
model. Due to the continuity equation, the correlation functions for the charge
and the current are directly connected: the parameters of the effective
hydrodynamic model thus determine the optical conductivity. Here we investigate
the validity of the proposed hydrodynamic theory in the full range of
parameters of the Hubbard model. In the non-interacting case, there is no
effective hydrodynamics, and the charge fluctuations present a rich variety of
non-universal behaviors. At weak coupling, the optical conductivity is
consistent with the hydrodynamic theory: at low frequency one observes a
Lorentzian-shaped Drude peak, but the high-frequency asymptotics is necessarily
different; the high-temperature limit for the product of the two hydrodynamic
model parameters is also in agreement with numerical data. At strong coupling,
we find that a generalization of the proposed hydrodynamic law is consistent
with our quantum Monte Carlo, as well as the finite-temperature Lanczos results
from literature. Most importantly, the temperature dependence of the
hydrodynamic parameters as well as the dc resistivity are found to be very
similar in the weak and the strong-coupling regimes.Comment: 27 pages, 23 figure
Dipole representation of half-filled Landau level
We introduce a variant of dipole representation for composite fermions in a
half-filled Landau level, taking into account the symmetry under exchange of
particles and holes. This is implemented by a special constraint on composite
fermion and composite hole degree of freedom (of an enlarged space), that makes
the resulting composite particle, dipole, a symmetric object. We study an
effective Hamiltonian, that commutes with the constraint on the physical space,
and fulfills the requirement for boost invariance on the Fermi level. The
calculated Fermi liquid parameter F2 is in a good agreement with numerical
investigations in [Phys. Rev. Lett. 121, 147601 (2018)].Comment: 9 pages, 4 figure
Charge fluctuations, hydrodynamics and transport in the square-lattice Hubbard model
25 pages, 21 figuresRecent experimental results suggest that a particular hydrodynamic theory describes charge fluctuations at long wavelengths in the square-lattice Hubbard model. Due to the continuity equation, the correlation functions for the charge and the current are directly connected: the parameters of the effective hydrodynamic model thus determine the optical conductivity. Here we investigate the validity of the proposed hydrodynamic theory in the full range of parameters of the Hubbard model. In the non-interacting case, there is no effective hydrodynamics, and the charge fluctuations present a rich variety of non-universal behaviors. At weak coupling, the optical conductivity is consistent with the hydrodynamic theory: at low frequency one observes a Lorentzian-shaped Drude peak, and the high-temperature limit for the relation between the two hydrodynamic model parameters is reproduced; However, the high-frequency asymptotics is necessarily different. At strong coupling, we find that a generalized hydrodynamic law is consistent with our quantum Monte Carlo, as well as the finite-temperature Lanczos results from literature. Most importantly, the temperature dependence of the hydrodynamic parameters as well as the dc resistivity are found to be very similar in the weak and the strong-coupling regimes
Charge fluctuations, hydrodynamics and transport in the square-lattice Hubbard model
25 pages, 21 figuresRecent experimental results suggest that a particular hydrodynamic theory describes charge fluctuations at long wavelengths in the square-lattice Hubbard model. Due to the continuity equation, the correlation functions for the charge and the current are directly connected: the parameters of the effective hydrodynamic model thus determine the optical conductivity. Here we investigate the validity of the proposed hydrodynamic theory in the full range of parameters of the Hubbard model. In the non-interacting case, there is no effective hydrodynamics, and the charge fluctuations present a rich variety of non-universal behaviors. At weak coupling, the optical conductivity is consistent with the hydrodynamic theory: at low frequency one observes a Lorentzian-shaped Drude peak, and the high-temperature limit for the relation between the two hydrodynamic model parameters is reproduced; However, the high-frequency asymptotics is necessarily different. At strong coupling, we find that a generalized hydrodynamic law is consistent with our quantum Monte Carlo, as well as the finite-temperature Lanczos results from literature. Most importantly, the temperature dependence of the hydrodynamic parameters as well as the dc resistivity are found to be very similar in the weak and the strong-coupling regimes