scholarly journals A Weyl-Z2 semimetal from holography

2021 ◽  
Vol 2021 (12) ◽  
Author(s):  
Xuanting Ji ◽  
Yan Liu ◽  
Ya-Wen Sun ◽  
Yun-Long Zhang
Keyword(s):  
Quantum Phase Transitions ◽  
Transport Coefficients ◽  
Effective Field ◽  
Anomalous Transport ◽  
Hall Conductivity ◽  
Chiral Anomaly ◽  
Transport Parameters ◽  
Strongly Coupled ◽  
Topological Quantum ◽  
Two Parameters

Abstract We present effective field theories for the weakly coupled Weyl-Z2 semimetal, as well as the holographic realization for the strongly coupled case. In both cases, the anomalous systems have both the chiral anomaly and the Z2 anomaly and possess topological quantum phase transitions from the Weyl-Z2 semimetal phases to partly or fully topological trivial phases. We find that the topological phase transition is characterized by the anomalous transport parameters, i.e. the anomalous Hall conductivity and the Z2 anomalous Hall conductivity. These two parameters are nonzero at the Weyl-Z2 semimetal phase and vanish at the topologically trivial phases. In the holographic case, the different behavior between the two anomalous transport coefficients is discussed. Our work reveals the novel phase structure of strongly interacting Weyl-Z2 semimetal with two pairs of nodes.

scholarly journals Chiral hydrodynamics in strong external magnetic fields

2021 ◽  
Vol 2021 (4) ◽  
Author(s):  
Martin Ammon ◽  
Sebastian Grieninger ◽  
Juan Hernandez ◽  
Matthias Kaminski ◽  
Roshan Koirala ◽  
...  
Keyword(s):  
Energy Momentum Tensor ◽  
Transport Coefficients ◽  
Momentum Tensor ◽  
Effective Field ◽  
Quantum Fluids ◽  
Hall Conductivity ◽  
Hydrodynamic Description ◽  
Strongly Coupled ◽  
Charge Current ◽  
Transport Effects

Abstract We construct the general hydrodynamic description of (3+1)-dimensional chiral charged (quantum) fluids subject to a strong external magnetic field with effective field theory methods. We determine the constitutive equations for the energy-momentum tensor and the axial charge current, in part from a generating functional. Furthermore, we derive the Kubo formulas which relate two-point functions of the energy-momentum tensor and charge current to 27 transport coefficients: 8 independent thermodynamic, 4 independent non-dissipative hydrodynamic, and 10 independent dissipative hydrodynamic transport coefficients. Five Onsager relations render 5 more transport coefficients dependent. We uncover four novel transport effects, which are encoded in what we call the shear-induced conductivity, the two expansion-induced longitudinal conductivities and the shear-induced Hall conductivity. Remarkably, the shear-induced Hall conductivity constitutes a novel non-dissipative transport effect. As a demonstration, we compute all transport coefficients explicitly in a strongly coupled quantum fluid via holography.

scholarly journals Critical behaviour of hydrodynamic series

2021 ◽  
Vol 2021 (5) ◽  
Author(s):  
M. Asadi ◽  
H. Soltanpanahi ◽  
F. Taghinavaz
Keyword(s):  
Chemical Potential ◽  
Transport Coefficients ◽  
Hydrodynamic Modes ◽  
Third Order ◽  
Hydrodynamic Mode ◽  
Strongly Coupled ◽  
Conformal Theory ◽  
Shear Dispersion ◽  
Type Iib String Theory ◽  
Hydrodynamic Transport

Abstract We investigate the time-dependent perturbations of strongly coupled $$ \mathcal{N} $$ N = 4 SYM theory at finite temperature and finite chemical potential with a second order phase transition. This theory is modelled by a top-down Einstein-Maxwell-dilaton description which is a consistent truncation of the dimensional reduction of type IIB string theory on AdS5×S5. We focus on spin-1 and spin-2 sectors of perturbations and compute the linearized hydrodynamic transport coefficients up to the third order in gradient expansion. We also determine the radius of convergence of the hydrodynamic mode in spin-1 sector and the lowest non-hydrodynamic modes in spin-2 sector. Analytically, we find that all the hydrodynamic quantities have the same critical exponent near the critical point θ = $$ \frac{1}{2} $$ 1 2 . Moreover, we propose a relation between symmetry enhancement of the underlying theory and vanishing of the only third order hydrodynamic transport coefficient θ1, which appears in the shear dispersion relation of a conformal theory on a flat background.

Anomalous transport coefficients in a magnetized turbulent plasma

1982 ◽  
Vol 28 (2) ◽  
pp. 193-214 ◽  
Author(s):  
Qiu Xiaoming ◽  
R. Balescu
Keyword(s):  
Transport Coefficients ◽  
Collision Operator ◽  
Turbulent Plasma ◽  
Anomalous Transport ◽  
Weak Turbulence ◽  
Dissipative Effects ◽  
Dependent Transport ◽  
Two Fluid ◽  
Two Fluid Plasma

In this paper we generalize the formalism developed by Balescu and Paiva-Veretennicoff, valid for any kind of weak turbulence, for the determination of all the transport coefficients of an unmagnetized turbulent plasma, to the case of a magnetized one, and suggest a technique to avoid finding the inverse of the turbulent collision operator. The implicit plasmadynamical equations of a two-fluid plasma are presented by means of plasmadynamical variables. The anomalous transport coefficients appear in their natural places in these equations. It is shown that the necessary number of transport coefficients for describing macroscopically the magnetized turbulent plasma does not exceed the number for the unmagnetized one. The typical turbulent and gyromotion terms, representing dissipative effects peculiar to the magnetized system, which contribute to the frequency-dependent transport coefficients are clearly exhibited.

scholarly journals Quantum critical scaling and holographic bound for transport coefficients near Lifshitz points

2020 ◽  
Vol 2020 (11) ◽  
Author(s):  
Gian Andrea Inkof ◽  
Joachim M. C. Küppers ◽  
Julia M. Link ◽  
Blaise Goutéraux ◽  
Jörg Schmalian
Keyword(s):  
Field Theory ◽  
Transport Coefficients ◽  
Massless Scalar ◽  
Famous Conjecture ◽  
Strongly Coupled ◽  
Spatial Anisotropy ◽  
Anisotropic Scaling ◽  
Geometric Ratio ◽  
Anisotropic Systems ◽  
Gauge Gravity

Abstract The transport behavior of strongly anisotropic systems is significantly richer compared to isotropic ones. The most dramatic spatial anisotropy at a critical point occurs at a Lifshitz transition, found in systems with merging Dirac or Weyl point or near the superconductor-insulator quantum phase transition. Previous work found that in these systems a famous conjecture on the existence of a lower bound for the ratio of a shear viscosity to entropy is violated, and proposed a generalization of this bound for anisotropic systems near charge neutrality involving the electric conductivities. The present study uses scaling arguments and the gauge-gravity duality to confirm the previous analysis of universal bounds in anisotropic Dirac systems. We investigate the strongly-coupled phase of quantum Lifshitz systems in a gravitational Einstein-Maxwell-dilaton model with a linear massless scalar which breaks translations in the boundary dual field theory and sources the anisotropy. The holographic computation demonstrates that some elements of the viscosity tensor can be related to the ratio of the electric conductivities through a simple geometric ratio of elements of the bulk metric evaluated at the horizon, and thus obey a generalized bound, while others violate it. From the IR critical geometry, we express the charge diffusion constants in terms of the square butterfly velocities. The proportionality factor turns out to be direction-independent, linear in the inverse temperature, and related to the critical exponents which parametrize the anisotropic scaling of the dual field theory.

COLLECTIVE FIELD THEORY TO MAGNETIC-FIELD-INDUCED SPIN-DENSITY-WAVE-STATE IN BECHGAARD SALTS, (TMTSF)2X

1993 ◽  
Vol 07 (19) ◽  
pp. 3415-3421 ◽  
Author(s):  
ALEXANDRE S. ROZHAVSKY
Keyword(s):  
Magnetic Field ◽  
Spin Density ◽  
Chemical Potential ◽  
Density Wave ◽  
Spin Density Wave ◽  
Hall Conductivity ◽  
Chiral Anomaly ◽  
Threshold Field ◽  
Wave State ◽  
Extended States

A field description of spin-density-wave (SDW) in a quasi-two-dimensional metal with open Fermi surface in magnetic field, is proposed. The SDW transition temperature, T c (H), and the Hall conductivity σxy, are calculated. The dependence T c (H) is found to be different from that of the Bardeen-Cooper-Schrieffer model, in particular, a threshold field, H c , found its natural explanation. It is proved that the quantized Hall conductivity arises from the chiral anomaly terms in the effective action provided there is pinning of chemical potential in the gap of extended states.

scholarly journals Quasiparticles as detector of topological quantum phase transitions

2020 ◽  
Vol 2 (4) ◽  
Author(s):  
Sourav Manna ◽  
N. S. Srivatsa ◽  
Julia Wildeboer ◽  
Anne E. B. Nielsen
Keyword(s):  
Phase Transitions ◽  
Quantum Phase Transitions ◽  
Quantum Phase ◽  
Topological Quantum

Probing topological quantum phase transitions via photonic spin Hall effects in spin-orbit coupled 2D quantum materials

2021 ◽  
Author(s):  
Muzamil Shah
Keyword(s):  
Phase Transitions ◽  
Hall Effect ◽  
Extreme Values ◽  
Optical Transition ◽  
Quantum Phase Transitions ◽  
Measurement Techniques ◽  
Quantum Phase ◽  
Spin Hall Effect ◽  
Radiation Fields ◽  
Topological Quantum

Abstract Topological photonics is an emerging field in photonics in which various topological and geometrical ideas are used to manipulate and control the behavior of light photons. The interplay between topological matter and the spin degree of freedom of photons provides new opportunities for achieving spin-based photonics applications. In this paper, the photonic spin Hall effect (PSHE) of reflected light from the surface of the topological silicene quantum systems subjected to external electric and radiation fields in the terahertz regime is theoretically investigated. By tuning the external electric and the applied laser fields, we can drive the silicenic system through different topological quantum phase transitions. We demonstrate that the in-plane and transverse spatial spin dependent shifts exhibit extreme values near Brewster’s angles and away from the optical transition frequencies. We reveal that the photonic spin Hall shifts are sensitive to the spin and valley indices as well as to the number of closed gaps. By incorporating the quantum weak value measurement techniques, the photonic spin Hall effect greatly impact the research in spinoptics, spintronics, and valleytronics.

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