Charge density waves in Weyl semimetals

Sehayek, Dan; Thakurathi, Manisha; Burkov, A. A.

doi:10.1103/physrevb.102.115159

Cited by 31 publications

(23 citation statements)

References 61 publications

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“…Recently, a stable DDP and topological stepedge modes were experimentally measured in the CDW phase of the T -symmetric Dirac semimetal TaTe 4 [132], providing further support for the analysis performed in this work. Additionally, recently, an analysis of minimal Weyl-CDWs beyond mean-field theory was performed in [113]; the analysis in [113] explicitly confirms our characterization of the mean-field QAH and oQAH phases of Weyl-CDWs. Lastly, recently, Ref.…”

supporting

confidence: 69%

“…Next, we emphasize that the axionic response in Weyl-CDWs is measurable through the dynamical dependence of the quasi-2D QAH effect on φ, rather than through the static magnetoelectric polarizability at fixed φ [111,112]. Furthermore, solitonlike defects in φ, which carry the same half-quantized Hall conductivity as gapped AXI surfaces for δθ φ = π [113], can in principle be manipulated by exciting the CDW sliding mode. Finally, in I-symmetric, magnetic Weyl-CDWs, our results highlight the experimental and theoretical difficulty of distinguishing QAH, oQAH, and AXI phases.…”

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confidence: 99%

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Axionic band topology in inversion-symmetric Weyl-charge-density waves

Wieder

Lin

Bradlyn

2020

Phys. Rev. Research

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In recent theoretical and experimental investigations, researchers have linked the low-energy field theory of a Weyl semimetal gapped with a charge-density wave (CDW) to high-energy theories with axion electrodynamics. However, it remains an open question whether a lattice regularization of the dynamical Weyl-CDW is in fact a single-particle axion insulator (AXI). In this Rapid Communication, we use analytic and numerical methods to study both lattice-commensurate and incommensurate minimal (magnetic) Weyl-CDW phases in the mean-field state. We observe that, as previously predicted from field theory, the two inversion (I)-symmetric Weyl-CDWs with φ = 0, π differ by a topological axion angle δθ φ = π. However, we crucially discover that neither of the minimal Weyl-CDW phases at φ = 0, π is individually an AXI; they are instead quantum anomalous Hall (QAH) and "obstructed" QAH insulators that differ by a fractional translation in the modulated cell, analogous to the two phases of the Su-Schrieffer-Heeger model of polyacetylene. Using symmetry indicators of band topology and non-Abelian Berry phase, we demonstrate that our results generalize to multiband systems with only two Weyl fermions, establishing that minimal Weyl-CDWs unavoidably carry nontrivial Chern numbers that prevent the observation of a static magnetoelectric response. We discuss the experimental implications of our findings and provide models and analysis generalizing our results to nonmagnetic Weyl-and Dirac-CDWs.

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confidence: 69%

mentioning

confidence: 99%

Axionic band topology in inversion-symmetric Weyl-charge-density waves

Wieder

Lin

Bradlyn

2020

Phys. Rev. Research

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“…In particular, the elasticity tetrads are important in the field theory description of the intrinsic (without external magnetic field) quantum Hall effect in 3D topological and axion insulators [31,[54][55][56]. The corresponding topological response contains the elasticity tetrad as a dynamical lattice gauge field combined with the electromagnetic gauge field with the Chern-Simons topological term [3,20,[57][58][59]:…”

Section: Anomalous Qhe In 3d Topological Insulatorsmentioning

confidence: 99%

Topological polarization, dual invariants, and surface flat bands in crystalline insulators

2021

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We describe a crystalline topological insulator (TI) phase of matter that exhibits spontaneous polarization in arbitrary dimensions. The bulk polarization response is constructed by coupling the system to geometric deformations of the underlying crystalline order, represented by local lattice vectors-the elasticity tetrads. This polarization results from the presence of (approximately) flat bands on the surface of such TIs. These flat bands are a consequence of the bulk-boundary correspondence of polarized topological media, and contrary to related nodal line semimetal phases also containing surface flat bands, they span the entire surface Brillouin zone. We also present an example Hamiltonian exhibiting a Lifshitz transition from the nodal line phase to the TI phase with polarization. In addition, we discuss a general classification of three-dimensional (3D) crystalline TI phases and invariants in terms of the elasticity tetrads. The phase with polarization naturally arises from this classification as a dual to the previously better-known 3D TI phase exhibiting quantum (spin) Hall effect. Besides polarization, another implication of the large surface flat band is the susceptibility to interaction effects such as superconductivity: The mean-field critical temperature is proportional to the size of the flat bands, and this type of system may hence exhibit superconductivity with a very high critical temperature.

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“…Unlike Ref. 68 , we do not study the microscopic origin of the CDW order parameter in this work, as the main goal of introducing the TB model is simply to provide a UV completion of the low-energy theory on which our analysis is rigorously based. In particular, the CDW that we introduce is commensurate to the original lattice, resulting in reduced lattice translation symmetries with the new lattice constants given by a ′…”

Section: Tb Realization Of the Dpmementioning

confidence: 99%

Dynamical Piezomagnetic Effect in Time-Reversal-Invariant Weyl Semimetals with Axionic Charge-Density Waves

Wieder

Liu

2021

Preprint

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We predict that dynamical strain can induce a bulk orbital magnetization in time-reversal- (TR-) invariant Weyl semimetals (WSMs) that are gapped by charge-density waves (CDWs) -- a class of systems experimentally observed this past year. We term this effect the ``dynamical piezomagnetic effect" (DPME). By studying the low-energy effective theory and a minimal tight-binding (TB) model, we find that the DPME originates from an effective valley axion field that couples the electromagnetic gauge field with a strain-induced pseudo-gauge field. In particular, the DPME represents the first example of a fundamentally 3D strain effect originating from the Chern-Simons 3-form, in contrast to the previously-studied piezoelectric effects characterized by 2D Berry curvature. We further find that the DPME has a discontinuous change when the surface of the system undergoes a topological quantum phase transition (TQPT), and thus, that the DPME provides a bulk signature of a boundary TQPT in a TR-invariant Weyl-CDW.

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Charge density waves in Weyl semimetals

Cited by 31 publications

References 61 publications

Axionic band topology in inversion-symmetric Weyl-charge-density waves

Axionic band topology in inversion-symmetric Weyl-charge-density waves

Topological polarization, dual invariants, and surface flat bands in crystalline insulators

Dynamical Piezomagnetic Effect in Time-Reversal-Invariant Weyl Semimetals with Axionic Charge-Density Waves

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