Weyl semimetal non-equilibrium setting with distinct chemical potentials
We studied the non-linear transport signatures of electrochemical forces on the prototypical Weyl semimetal as well as nodal line semimetals. The first has a quantized response when the chemical potential is distinct for each Weyl node, while the last one has a parity anomaly response that wee verify survives for finite temperatures.
References
2023
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Electrochemical transport in Dirac nodal-line semimetals
R. Flores-Calderón, Leonardo Medel, and A. Martín-Ruiz
Europhysics Letters, Jun 2023
Publisher: EDP Sciences, IOP Publishing and Società Italiana di Fisica
Nodal-line semimetals are topological phases where the conduction and the valence bands cross each other along one-dimensional lines in the Brillouin zone, which are symmetry protected by either spatial symmetries or time-reversal symmetry. In particular, nodal lines protected by the combined symmetry exhibits the parity anomaly of 2D Dirac fermions. In this letter, we study the electrochemical transport in Dirac nodal-line semimetals by using the semiclassical Boltzmann equation approach. We derive a general formula for the topological current that includes both the Berry curvature and the orbital magnetic moment. We first evaluate the electrochemical current by introducing a small mass term (which could be induced by inversion-breaking uniaxial strain, pressure, or an external electric field) and apply it to the hexagonal pnictide CaAgP. The electrochemical current vanishes in the zero-mass limit. Introducing a tilting term that does not spoil symmetry that protects the nodal ring, we obtain a finite electrochemical current in the zero-mass limit, which can be regarded as a direct consequence of the parity anomaly. We show that the parity-anomaly–induced electrochemical transport is also present at nonzero temperatures.
2021
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Quantized electrochemical transport in Weyl semimetals
R. Flores-Calderón, and A. Martı́n-Ruiz
Phys. Rev. B, Jan 2021
We show that under the effect of an external electric field and a gradient of chemical potential, a topological electric current can be induced in Weyl semimetals without inversion and mirror symmetries. We derive analytic expressions for the nonlinear conductivity tensor and show that it is nearly quantized for small tilting when the Fermi levels are close to the Weyl nodes. When the Van Hove point is much larger than the largest Fermi level, the band structure is described by two linearly dispersing Weyl fermions with opposite chiralities. In this case, the electrochemical response is fully quantized in terms of fundamental constants and the scattering time, and it can be used to measure directly the topological charge of Weyl points. We show that the electrochemical chiral current may be derived from an electromagnetic action similar to axion electrodynamics, where the position-dependent chiral Fermi level plays the role of the axion field. This posits our results as a direct consequence of the chiral anomaly.
