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About eight years ago it was predicted theoretically that a charged chiral plasma could support the propagation of the so-called chiral magnetic waves, which are driven by the anomalous chiral magnetic and chiral separation effects. This prompted intensive experimental efforts in search of signatures of such waves in relativistic heavy-ion collisions. In fact, several experiments have already reported a tentative detection of the predicted signal, albeit with a significant background contribution. Here, we critically reanalyze the theoretical foundations for the existence of the chiral magnetic waves. We find that the commonly used background-field approximation is not sufficient for treating the waves in hot chiral plasmas in the long-wavelength limit. Indeed, the back-reaction from dynamically induced electromagnetic fields turns the chiral magnetic wave into a diffusive mode. While the situation is slightly better in the strongly-coupled near-critical regime of quark-gluon plasma created in heavy-ion collisions, the chiral magnetic wave is still strongly overdamped due to the effects of electrical conductivity and charge diffusion.
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Collective excitations in Weyl semimetals in the hydrodynamic regime
The spectrum of collective excitations in Weyl materials is studied by using a consistent hydro- dynamics. The corresponding framework includes the vortical and chiral anomaly effects, as well as the dependence on the separation between the Weyl nodes in energy b0 and momentum b. The latter are introduced via the Chern–Simons contributions to the electric current and charge densities in the Maxwell’s equations. It is found that, even in the absence of a background magnetic field, certain collective excitations (e.g., the helicon-like modes and anomalous Hall waves) are strongly affected by the chiral shift b. In a background magnetic field, the existence of distinctive longi- tudinal and transverse anomalous Hall waves with a linear dispersion relation is predicted. They originate from the oscillations of the electric charge density and electromagnetic fields, in which different components of the fields are connected via the anomalous Hall effect in Weyl semimetals.
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- PAR ID:
- 10059105
- Date Published:
- Journal Name:
- Journal of Physics: Condensed Matter
- Volume:
- 30
- Issue:
- 27
- ISSN:
- 0953-8984
- Page Range / eLocation ID:
- 275601
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1088/1361-648X/aac500
