Optical evidence of the chiral magnetic anomaly in the Weyl semimetal TaAs

Levy, Alan S.; Sushkov, A. B.; Liu, Fengguang; Shen, Bing; Ni, Ni; Drew, H. D.; Jenkins, Gregory S.

doi:10.1103/physrevb.101.125102

Cited by 24 publications

(21 citation statements)

References 33 publications

(30 reference statements)

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“…All optical conductivity measurements of the TaAs family compounds discussed above have been carried out on (001) surfaces, which have tetragonal crystallographic symmetry and no optical anisotropy. The out‐of‐plane response (with the electric‐field component of the probing light parallel to [001] direction) was studied by Levy et al [ 94 ] for TaAs. A linear increase in the low‐energy interband conductivity was also observed for this polarization at the energies below 25 meV.…”

Section: Linear Optical Response: Review Of Experimental Resultsmentioning

confidence: 99%

Nodal Semimetals: A Survey on Optical Conductivity

Pronin

Dressel

2020

Physica Status Solidi (b)

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Among different topological and related phases of condensed matter, nodal semimetals occupy a special place -the electronic band topology in these materials is related to three-dimensional bulk, rather than to surface, states. A great variety of different realizations of electronic band crossings (the nodes) leads to a plethora of different electronic properties, ranging from the chiral anomaly to solid-state realizations of a black-hole horizon. The different nodal phases have similar low-energy band structure and quasiparticle dynamics, which both can be accessed experimentally by a number of methods. Optical measurements with their large penetration depth and high energy resolution are ideally suited as such a bulk probe; especially at low energies where other spectroscopic methods often lack the required resolution. In this contribution, we review recent optical-conductivity studies of different nodal semimetals, discuss possible limitations of such measurements, and provide a comparison between the experimental results, simple theoretical models, and band-structure-based calculations.

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Section: Linear Optical Response: Review Of Experimental Resultsmentioning

confidence: 99%

Nodal Semimetals: A Survey on Optical Conductivity

Pronin

Dressel

2020

Physica Status Solidi (b)

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“…[ 6–8 ] Early on, most of the exploratory studies focused on assessing the special features of WSMs by direct probing of the electronic structure such as via angle‐resolved photoemission [ 9–11 ] and scanning tunneling spectroscopy. [ 12–14 ] Recently, interest has focused on the exploitation of the unusual properties of their electronic structure to observe unique physical phenomena, such as the chiral [ 15–17 ] and axial‐gravitational anomaly, [ 18 ] the circular photogalvanic effect, [ 19–20 ] chiral sound waves, [ 21–22 ] the surface‐state enhanced Edelstein effect [ 23 ] or the recently proposed chiral Hall‐effect. [ 24 ] The observation of most of these effects depends on whether the topological electronic states of the WSMs can be readily accessed.…”

Section: Introductionmentioning

confidence: 99%

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confidence: 99%

Large Fermi‐Energy Shift and Suppression of Trivial Surface States in NbP Weyl Semimetal Thin Films

et al. 2021

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properties of their electronic structure to observe unique physical phenomena, such as the chiral [15][16][17] and axial-gravitational anomaly, [18] the circular photogalvanic effect, [19][20] chiral sound waves, [21][22] the surface-state enhanced Edelstein effect [23] or the recently proposed chiral Hall-effect. [24] The observation of most of these effects depends on whether the topological electronic states of the WSMs can be readily accessed. In this regard, the ability to suppress non-topological (trivial) surface states, as well as to modify the Fermi-level position to get a desired Fermi surface topology, would allow full access to unveil the role of topological surface states on physical observables, and, in addition, to construct on-demand Fermi-surfaces to harness electrical, acoustic or optical measurable outputs. So far, the diversity of electronic structures was achieved through exploring different WSMs, but a genuine control of the shape and size of topological bands in the same material has remained elusive, mostly due to the lack of bottom-up, ultrahigh-vacuum synthesis methods that allow for control of the surface termination and Fermi-level position, for instance by doping or strain. This challenge needs to be overcome to achieve Fermi-level engineered Weyl semimetal heterostructures, leading to a plethora of novel platforms to explore both fundamental phenomena and device applications based on topology.In this work, we show two striking modifications of the electronic structure of the type-I Weyl semimetal NbP, that become accessible due to a successful epitaxial thin film growth synthesis route. [25] First, a full suppression of the bowtie-like (trivial) surface states of NbP is obtained due to the saturation of surface dangling bonds by an ordered phosphorous termination, that manifests itself in a (√2 × √2) surface reconstruction. Second, by chemically doping the surface with Se-atoms, the Fermi-energy undergoes a substantial shift of around +0.3 eV (electron doping) while preserving the pristine NbP bandstructure features, thereby enabling the first experimental visualization of the topological band dispersion well above the Weyl points, and highlighting the large Fermi-level tunability that can be achieved by surface chemical doping in a molecular beam epitaxy process. Our work opens up the possibility of realizing recent theoretical proposals, such as a Weyl semimetal field effect transistor (WEYLFET) that relies on purely topological Weyl semimetals, a class of 3D topological materials, exhibit a unique electronic structure featuring linear band crossings and disjoint surface states (Fermi-arcs). While first demonstrations of topologically driven phenomena have been realized in bulk crystals, efficient routes to control the electronic structure have remained largely unexplored. Here, a dramatic modification of the electronic structure in epitaxially grown NbP Weyl semimetal thin films is reported, using in situ surface engineering and chemical doping strategies that do not alter the NbP...

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“…In this case, van Hove singularities (vHSs) in the density of states (DOS) are located at k // B = 0, and interband optical transitions from/to these vHSs are expected to dominate the optical conductivity spectrum. In the Voigt configuration, these optical transitions obey selection rules Δ |N | = ±1 for light polarization perpendicular to B and Δ| N | = 0 for polarization parallel to B ( 18 ).…”

Section: Resultsmentioning

confidence: 99%

“…This would pump charge from one Weyl point to its neighbor of opposite chirality, raising the chemical potential of one point with respect to the other and splitting the single onset at the quantum limit into two. Such charge pumping is known as the chiral anomaly of Weyl Fermions (18,(25)(26)(27)(28). Previous measurements of this effect relied on DC transport, which suffered from ambiguity due to other possible trivial effects (29)(30)(31).…”

Section: Discussionmentioning

confidence: 99%