Magneto-optics of massless Kane fermions: Role of the flat band and unusual Berry phase

Malcolm, John D.; Nicol, E. J.

doi:10.1103/physrevb.92.035118

Cited by 112 publications

(100 citation statements)

References 15 publications

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“…The Landau level energy of the Kane fermion takes a similar form of field dependence but differs in the zeroth Landau level and spin splitting [43]. As a result of its unique Landau level spectrum, the Berry phase of the Kane model is non-π -quantized unlike massless Dirac systems and varies with model parameters, gap size, and spin-orbit coupling [44]. It also differs from the conventional systems with a quadratic band in which the Berry phase is always trivial.…”

Section: Resultsmentioning

confidence: 99%

Evidence for pressure-induced node-pair annihilation in Cd3As2

et al. 2017

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We report a magnetotransport study of Dirac semimetal Cd 3 As 2 under high pressure. The Shubnikov-de Haas oscillations are measured at different pressures to reveal the evolution of the Fermi surface. A sudden change in the phase factor of the oscillations occurs at 1.3 GPa along with the unanticipated shrinkage of the Fermi surface, which is well below the structure transition point from the tetragonal to the monoclinic structure (∼2.5 GPa). High-pressure x-ray diffraction also reveals an anisotropic compression of the Cd 3 As 2 lattice around a similar pressure. Through the first-principles calculations, we find that such axial compression along the c direction will shift the Dirac nodes towards the Brillouin zone center and will eventually introduce a finite energy gap. Our result unveils a possible topological phase transition in pressurized Cd 3 As 2 without structure transition.

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Section: Resultsmentioning

confidence: 99%

Evidence for pressure-induced node-pair annihilation in Cd3As2

et al. 2017

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“…This material has been described as a system with massless fermions with a low-energy bandstructure which has Dirac cones and a flat band at the Dirac point. Contributions to the interband conductivity arise from both transitions from the flat band to the Dirac cone and between the cones 31,86 , analogous to what is studied here, and theory predicts a linear conductivity 31,87 . This system can be understood as a superposition between a pseudospin 1/2 and pseudospin 1 3D DSM 86,88 and, hence, it fits with our discussion.…”

Section: Including a Massless Gapmentioning

confidence: 96%

“…Contributions to the interband conductivity arise from both transitions from the flat band to the Dirac cone and between the cones 31,86 , analogous to what is studied here, and theory predicts a linear conductivity 31,87 . This system can be understood as a superposition between a pseudospin 1/2 and pseudospin 1 3D DSM 86,88 and, hence, it fits with our discussion. Overall, it is clear that the optical conductivity of a number of materials has been measured and the unusual linear conductivity suggesting 3D Dirac cones has been seen although some details differ.…”

Section: Including a Massless Gapmentioning

confidence: 96%

Erratum: Optical and transport properties in three-dimensional Dirac and Weyl semimetals [Phys. Rev. B93, 085426 (2016)]

Tabert¹,

Ćarbotte²,

Nicol³

2016

Phys. Rev. B

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Within a Kubo formalism, we study dc transport and ac optical properties of 3D Dirac and Weyl semimetals. Emphasis is placed on the approach to charge neutrality and on the differences between Dirac and Weyl materials. At charge neutrality, the zero-temperature limit of the dc conductivity is not universal and also depends on the residual scattering model employed. However, the Lorenz number L retains its usual value L0. With increasing temperature, the Wiedemann-Franz law is violated. At high temperatures, L exhibits a new plateau at a value dependent on the details of the scattering rate. Such details can also appear in the optical conductivity, both in the Drude response and interband background. In the clean limit, the interband background is linear in photon energy and always extrapolates to the origin. This background can be shifted to the right through the introduction of a massless gap. In this case, the extrapolation can cut the axis at a finite photon energy as is observed in some experiments. It is also of interest to differentiate between the two types of Weyl semimetals: those with broken time-reversal symmetry and those with broken spatialinversion symmetry. We show that, while the former will follow the same behaviour as the 3D Dirac semimetals, for the zero magnetic field properties discussed here, the latter type will show a double step in the optical conductivity at finite doping and a single absorption edge at charge neutrality. The Drude conductivity is always finite in this case, even at charge neutrality.

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“…For instance, there exists a correspondence between our model and massless Kane fermion systems 50,51 that can arise in 3D zinc-blende crystals, i.e., Hg 1−x Cd x Te, at some critical doping concentration [52][53][54] . In particular, for singular Berry flux Φ = 1/2 (α = 1/ √ 3), we have…”

Section: Discussionmentioning

confidence: 80%

“…In recent experiments [52][53][54] , exotic Dirac-like quasiparticles named massless Kane fermions have been observed in 3D zinc-blende crystals, i.e., Hg 1−x Cd x Te, at some critical doping concentration. In the presence of strong spin-orbit interaction (e.g., ∼ 1eV), the fermions can be effectively described by the six-band Kane Hamiltonian…”

Section: Appendix F: Extrinsic Versus Intrinsic Valley Hall Effectmentioning

confidence: 99%

Geometric valley Hall effect and valley filtering through a singular Berry flux

Huang

et al. 2017

Phys. Rev. B

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Conventionally, a basic requirement to generate valley Hall effect (VHE) is that the Berry curvature for conducting carriers in the momentum space be finite so as to generate anomalous deflections of the carriers originated from distinct valleys into different directions. We uncover a geometric valley Hall effect (gVHE) in which the valley-contrasting Berry curvature for carriers vanishes completely except for the singular points. The underlying physics is a singular non-π fractional Berry flux located at each conical intersection point in the momentum space, analogous to the classic AharonovBohm effect of a confined magnetic flux in real space. We demonstrate that, associated with gVHE, exceptional skew scattering of valley-contrasting quasiparticles from a valley-independent, scalar type of impurities can generate charge neutral, transverse valley currents. As a result, the massless nature of the quasiparticles and their high mobility are retained. We further demonstrate that, for the particular Berry flux of π/2, gVHE is considerably enhanced about the skew scattering resonance, which is electrically controllable. A remarkable phenomenon of significant practical interest is that, associated with gVHE, highly efficient valley filtering can arise. These phenomena are robust against thermal fluctuations and disorders, making them promising for valleytronics applications.

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Magneto-optics of massless Kane fermions: Role of the flat band and unusual Berry phase

Cited by 112 publications

References 15 publications

Evidence for pressure-induced node-pair annihilation in Cd3As2

Evidence for pressure-induced node-pair annihilation in Cd3As2

Erratum: Optical and transport properties in three-dimensional Dirac and Weyl semimetals [Phys. Rev. B93, 085426 (2016)]

Geometric valley Hall effect and valley filtering through a singular Berry flux

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