Riemann tensor of the ambient universe, the dilaton, and Newton’s constant

Ivanov, Rossen I.; Prodanov, Emil M.

doi:10.1103/physrevd.70.044013

Cited by 38 publications

(79 citation statements)

References 21 publications

(12 reference statements)

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“…(3) Although Ψ SF is unstable toward phase separation for t ′ /t ∼ 0 in accordance with the feature in the t-J model, 61 Ψ SF restores stability against inhomogeneity for t ′ /t ∼ −0.3. This aspect is similar to that of AF states.…”

Section: Discussionmentioning

confidence: 55%

“…35,38,[112][113][114] For the t-J model, an SF state has also been shown to be unstable toward phase separation in a wide range of δ for t ′ /t = 0. 61 Therefore, we need to check this instability in the present case. To this end, we consider the charge compressibility κ or equivalently the charge susceptibility χ c (= n 2 κ), the inverse of which is given as…”

Section: Frustrated Square Latticementioning

confidence: 96%

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Staggered Flux State in Two-Dimensional Hubbard Models

2016

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The stability and other properties of a staggered flux (SF) state or a correlated d-density wave state are studied for the Hubbard (t-t ′ -U) model on extended square lattices, as a low-lying state that competes with the d x 2 −y 2 -wave superconductivity (d-SC) and possibly causes the pseudogap phenomena in underdoped high-T c cuprates and organic κ-BEDT-TTF salts. In calculations, a variational Monte Carlo method is used. In the trial wave function, a configurationdependent phase factor, which is vital to treat a current-carrying state for a large U/t, is introduced in addition to ordinary correlation factors. Varying U/t, t ′ /t, and the doping rate (δ) systematically, we show that the SF state becomes more stable than the normal state (projected Fermi sea) for a strongly correlated (U/t 5) and underdoped (δ 0.16) area. The decrease in energy is sizable, particularly in the area where Mott physics prevails and the circular current (order parameter) is strongly suppressed. These features are consistent with those for the t-J model. The effect of the frustration t ′ /t plays a crucial role in preserving charge homogeneity and appropriately describing the behavior of holeand electron-doped cuprates and κ-BEDT-TTF salts. We argue that the SF state does not coexist with d-SC and is not a 'normal state' from which d-SC arises. We also show that a spin current (flux or nematic) state is never stabilized in the same regime.

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Section: Discussionmentioning

confidence: 55%

Section: Frustrated Square Latticementioning

confidence: 96%

Staggered Flux State in Two-Dimensional Hubbard Models

2016

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“…[12] With such a numerical work, it has been established that the elementary excitations are indeed visons, that is the gap in the vison excitation sector (non-local in terms of dimers) is lower than that in the dimer sector. [13] Dimer excitations are then interpreted as composite two-vison states.…”

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confidence: 99%

Crystallization of the resonating valence bond liquid as vortex condensation

et al. 2007

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We show that the liquid-to-crystal quantum phase transition in the Rokhsar-Kivelson dimer model on the two-dimensional triangular lattice occurs as a condensation of vortex-like excitations called "visons". This conclusion is drawn from the numerical studies of the vison spectrum in the liquid phase by using the Green's function Monte Carlo method. We find that visons remain the lowest excitation throughout the liquid phase and that their gap decreases continuously to zero at the phase transition. The nature of the crystal phase and the second order of the phase transition are in agreement with the earlier prediction of Moessner and Sondhi [Phys. Rev. B 63, 224401 (2001)].The resonating valence bond (RVB) liquid is one of the most intriguing concepts of today's condensed-matter physics. Conjectured over thirty years ago for frustrated spin systems, [1] it still lacks an adequate quantitative description, and even its emergence in real physical materials or in realistic spin models is not rigorously established. In the early days of the RVB paradigm, it has been realized that such a state should be characterized by a Z 2 topological order whose most prominent consequence is the vortex-like excitation [2] later dubbed "vison".[3] This type of excitations should be important for the thermodynamics of RVB spin liquids and serve as a "smoking gun" of the RVB phase. Numerically, low-lying singlet excitations have been found in the Kagome spin-1/2 Heisenberg antiferromagnet, [4] the most promising candidate for the RVB spin-liquid state, and these singlets have been interpreted as RVB states in the subspace of nearest-neighbor singlet dimers.[5] Experimentally, the spin-1/2 Kagome system with a possible spin-liquid phase has been realized recently in the ZnCu 3 (OH) 6 Cl 2 compound.[6] A variational study of this system with Gutzwiller-projected wave functions also predicts lowlying excitations of the gauge field [U(1) instead of Z 2 ]. [7] Thus the properties of the low-lying collective singlet excitations is one of the central questions in the study of RVB states.To model the vison branch of excitations in the RVB state, it has been proposed to use dimer models instead of spin ones. [8] In dimer models, the spin degrees of freedom are explicitly frozen, and only the vison excitations survive. Regardless of its relation to microscopic spin models, the quantum dimer model (QDM) of Rokhsar and Kivelson (RK) has attracted a lot of attention as a promising way to investigate RVB physics, especially on the triangular lattice. The QDM is defined by:where the sum runs over all plaquettes (rhombi) including the three possible orientations. The kinetic term controlled by the amplitude t flips the two dimers on every flippable plaquette, i.e., on every plaquette with two parallel dimers, while the potential term controlled by the interaction V describes a repulsion (V > 0) or an attraction (V < 0) between nearest-neighbor dimers. For dimer models, the situation is much more definite than for spin systems: The RVB phase is firml...

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“…Elementary excitations are visons [6,7], massive bosonic particles. The visons are non-local excitations; singlet density fluctuations involves at least two visons [8,9]. Vison-dispersion can be determined by Z 2 gauge theory [1,29].…”

Section: General Formulationmentioning

confidence: 99%

“…The low energy excitations are Z 2 vortices, "visons" [6,7]. While a single vison is a non-local object, excitations of even number of visons correspond to dimer density fluctuations [8,9].…”

Section: Introductionmentioning

confidence: 99%

Detecting nonmagnetic excitations in quantum magnets

Hao

2012

Phys. Rev. B

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Many unconventional quantum phases host special non-magnetic excitations such as photons and visons. We discuss two possible ways to detect these excitations experimentally. Firstly, spin-lattice coupling mixes the excitations with phonons. The phonon spectral function acquires new features that can be detected by neutron or X-ray scattering. Secondly, valence-bond fluctuations translate into charge density fluctuations on non-bipartite lattices. Such charge fluctuations can be characterized by conventional spectroscopies such as Terahertz spectroscopy. As by-products, we discuss the general mechanisms of spin-Peierls transitions in two and three dimensional spin liquids.

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Riemann tensor of the ambient universe, the dilaton, and Newton’s constant

Cited by 38 publications

References 21 publications

Staggered Flux State in Two-Dimensional Hubbard Models

Staggered Flux State in Two-Dimensional Hubbard Models

Crystallization of the resonating valence bond liquid as vortex condensation

Detecting nonmagnetic excitations in quantum magnets

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