Shanghai Key laboratory of High Temperature Superconductors

laboratory of, China

Shanghai Key laboratory of High Temperature Superconductors

laboratory of, China
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Ling Y.,CAS Institute of High Energy Physics | Ling Y.,Shanghai Key Laboratory of High Temperature Superconductors | Xian Z.,CAS Institute of High Energy Physics | Zhou Z.,CAS Institute of High Energy Physics
Journal of High Energy Physics | Year: 2016

In this paper we investigate the ratio of shear viscosity to entropy density, η/s, in hyperscaling violating geometry with lattice structure. We show that the scaling relation with hyperscaling violation gives a strong constraint to the mass of graviton and usually leads to a power law of temperature, η/s ∼ Tκ. We find the exponent κ can be greater than two such that the new bound for viscosity raised in [7] is violated. Our above observation is testified by constructing specific solutions with UV completion in various holographic models. Finally, we compare the boundedness of κ with the behavior of entanglement entropy and conjecture a relation between them. © 2016, The Author(s).


Ling Y.,CAS Institute of High Energy Physics | Ling Y.,Shanghai Key Laboratory of High Temperature Superconductors | Ling Y.,University of Chinese Academy of Sciences | Liu P.,CAS Institute of High Energy Physics | And 2 more authors.
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2017

In this note we remark that the butterfly effect can be used to diagnose the phase transition of superconductivity in a holographic framework. Specifically, we compute the butterfly velocity in a charged black hole background as well as anisotropic backgrounds with Q-lattice structure. In both cases we find its derivative to the temperature is discontinuous at critical points. We also propose that the butterfly velocity can signalize the occurrence of thermal phase transition in general holographic models. © 2017 The Authors


Ling Y.,CAS Institute of High Energy Physics | Ling Y.,Shanghai Key Laboratory of High Temperature Superconductors | Ling Y.,University of Chinese Academy of Sciences | Zheng X.,CAS Institute of High Energy Physics
Nuclear Physics B | Year: 2017

We construct a holographic model with Weyl corrections in five dimensional spacetime. In particular, we introduce a coupling term between the axion fields and the Maxwell field such that the momentum is relaxed even in the probe limit in this model. We investigate the Drude behavior of the optical conductivity in low frequency region. It is interesting to find that the incoherent part of the conductivity is suppressed with the increase of the axion parameter k/T, which is in contrast to other holographic axionic models at finite density. Furthermore, we study the superconductivity associated with the condensation of a complex scalar field and evaluate the critical temperature for condensation in both analytical and numerical manner. It turns out that the critical temperature decreases with k˜, indicating that the condensation becomes harder in the presence of the axions, while it increases with Weyl parameter γ. We also discuss the change of the gap in optical conductivity with coupling parameters. Finally, we evaluate the charge density of the superfluid in zero temperature limit, and find that it exhibits a linear relation with σ˜DC(Tc˜)Tc˜, such that a modified version of Homes’ law is testified. © 2017 The Authors


Kuang X.-M.,Pontifical Catholic University of Valparaíso | Wu J.-P.,Bohai University | Wu J.-P.,Shanghai Key Laboratory of High Temperature Superconductors
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2017

We obtain the black brane solution in arbitrary dimensional Gauss–Bonnet-axions (GBA) gravity theory. And then the thermal conductivity of the boundary theory dual to this neutral black brane is explored. We find that the momentum dissipation suppresses the DC thermal conductivity while it is enhanced by larger GB parameter. The analytical and numerical results of DC thermal conductivity match very well. Also we study the effect of the momentum dissipation and the GB coupling on the AC thermal conductivity and fit the results by Drude-like behavior for low frequency. Finally, we analytical compute the quasi-normal modes (QNM) frequency of the perturbative master field in large dimensions limit. Our analytical QNM frequencies agree well with the numerical results in large enough finite dimensions. © 2017 The Authors


Guo J.,Shanghai University | Guo J.,Shanghai Key Laboratory of High Temperature Superconductors | Zeng X.,Shanghai University | Yan M.,Shanghai University | Yan M.,Shanghai Key Laboratory of High Temperature Superconductors
Physical Review B | Year: 2017

The Dzyaloshinskii-Moriya interaction (DMI) can cause spin-wave (SW) nonreciprocality in extended magnetic films. Here, we report a correlated effect for SWs propagating in a waveguide, namely, a longitudinally magnetized nanowire. Due to the shape confinement, SWs traveling in the wire are quasiquantized along the width direction. In the presence of the DMI, the wave-front lines become oblique with respect to the propagation direction, unlike any ordinary wave pattern. The tilting direction of the wave front is determined by the sign of the DMI constant, manifesting the chiral nature of the DMI. Another remarkable SW property revealed is that the two dynamical magnetization components that jointly characterize a SW mode exhibit different spatial profiles. Mathematically, these extraordinary effects can be attributed to the first-order spatial derivative brought into the wave equation by the DMI. © 2017 American Physical Society.


Lan S.,Beijing Normal University | Liu W.,University of Chinese Academy of Sciences | Liu W.,Shanghai Key Laboratory of High Temperature Superconductors | Tian Y.,Beijing Normal University
Physical Review D | Year: 2017

We investigate in detail the m2=0 Abelian Higgs model in AdS4, which is considered as the holographic dual of the most BCS-like superfluid. In homogeneous and isotropic superfluid solutions, we calculate the fourth-sound speeds, the square of which approaches 1/2 with increasing chemical potential (lowering temperature). Then we present the single dark soliton solutions, which becomes thinner with increasing chemical potential. For the first time, we also find the interesting double and triple dark soliton solutions, which is unexpected and shows the possibility of more complicated static configurations. Finally, we investigate vortex solutions. For winding number n=1, the vortex becomes thinner with increasing chemical potential. At a given chemical potential, with increasing winding number, first the vortex becomes bigger and the charge density depletion becomes larger, and then the charge density depletion settles down at a certain value and the growth of the vortex size is found to obey a scaling symmetry. © 2017 American Physical Society.


Ling Y.,CAS Institute of High Energy Physics | Ling Y.,Shanghai Key Laboratory of High Temperature Superconductors | Liu P.,CAS Institute of High Energy Physics | Wu J.-P.,Bohai University | And 2 more authors.
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2017

We introduce a Weyl term into the Einstein–Maxwell-Axion theory in four dimensional spacetime. Up to the first order of the Weyl coupling parameter γ, we construct charged black brane solutions without translational invariance in a perturbative manner. Among all the holographic frameworks involving higher derivative gravity, we are the first to obtain metal-insulator transitions (MIT) when varying the system parameters at zero temperature. Furthermore, we study the holographic entanglement entropy (HEE) of strip geometry in this model and find that the second order derivative of HEE with respect to the axion parameter exhibits maximization behavior near quantum critical points (QCPs) of MIT. It testifies the conjecture in [1,2] that HEE itself or its derivatives can be used to diagnose quantum phase transition (QPT). © 2016 The Author(s)


Guo M.,Beijing Normal University | Lan S.,Beijing Normal University | Niu C.,Gwangju Institute of Science and Technology | Tian Y.,University of Chinese Academy of Sciences | And 3 more authors.
Classical and Quantum Gravity | Year: 2016

In this note, we have addressed various issues on zero temperature holographic superfluids. First, inspired by our numerical evidence for the equality between the superfluid density and particle density, we provide an elegant analytic proof for this equality by a boost trick. Second, using not only the frequency domain analysis but also the time domain analysis from numerical relativity, we identify the hydrodynamic normal modes and calculate out the sound speed, which is shown to increase with the chemical potential and saturate to the value predicted by the conformal field theory in the large chemical potential limit. Third, the generic non-thermalization is demonstrated by the fully nonlinear time evolution from a non-equilibrium state for our zero temperature holographic superfluid. Furthermore, a conserved Noether charge is proposed in support of this behavior. © 2016 IOP Publishing Ltd.


Fu G.,Bohai University | Wu J.-P.,Bohai University | Wu J.-P.,Shanghai Key Laboratory of High Temperature Superconductors | Xu B.,Bohai University | Liu J.,Bohai University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2017

In this letter, we study the charge response from higher derivatives over the background with homogeneous disorder introduced by axions. We first explore the bounds on the higher derivatives coupling from DC conductivity and the anomalies of causality and instabilities. Our results indicate no tighter constraints on the coupling than that over Schwarzschild-AdS (SS-AdS) background. And then we study the optical conductivity of our holographic system. We find that for the case with γ1<0 and the disorder strength αˆ<2/3, there is a crossover from a coherent to incoherent metallic phase as αˆ increases. When αˆ is beyond αˆ=2/3 and further amplified, a peak exhibits again at low frequency. But it cannot be well fitted by the standard Drude formula and new formula for describing this behavior shall be called for. While for the holographic system with the limit of γ1→1/48, the disorder effect drives the hard-gap-like at low frequency into the soft gap and suppresses the pronounced peak at medium frequency. © 2017 The Authors.


Wu J.-P.,Bohai University | Wu J.-P.,Shanghai Key Laboratory of High Temperature Superconductors
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2016

In this letter, we systematically explore the holographic (non-)relativistic fermionic spectrum without/with dipole coupling dual to Born-Infeld anti-de Sitter (BI-AdS) black hole. For the relativistic fermionic fixed point, this holographic fermionic system exhibits non-Fermi liquid behavior. Also, with the increase of BI parameter γ, the non-Fermi liquid becomes even "more non-Fermi". When the dipole coupling term is included, we find that the BI term makes it a lot tougher to form the gap. While for the non-relativistic fermionic system with large dipole coupling in BI-AdS background, with the increase of BI parameter, the gap comes into being again. © 2016 The Author.

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