Dirac Materials and Dirac Fermions

For the innovation of spintronic technologies, Dirac materials, in which low-energy excitation is described as relativistic Dirac fermions, are one of the most promising systems because of the fascinating magnetotransport associated with extremely high mobility. To incorporate Dirac fermions into spintronic applications, their quantum transport phenomena are desired to be manipulated to a large extent by magnetic order in a solid. We report a bulk half-integer quantum Hall effect in a layered antiferromagnet EuMnBi2, in which field-controllable Eu magnetic order significantly suppresses the interlayer coupling between the Bi layers with Dirac fermions. In addition to the high mobility of more than 10,000 cm2/V s, Landau level splittings presumably due to the lifting of spin and valley degeneracy are noticeable even in a bulk magnet. These results will pave a route to the engineering of magnetically functionalized Dirac materials.

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Moving Dirac nodes by chemical substitution

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2108617118 ◽

2021 ◽

Vol 118 (33) ◽

pp. e2108617118

Author(s):

Niloufar Nilforoushan ◽

Michele Casula ◽

Adriano Amaricci ◽

Marco Caputo ◽

Jonathan Caillaux ◽

...

Keyword(s):

Electronic Devices ◽

Metal Sulfide ◽

Dirac Fermions ◽

Metal Insulator ◽

Symmetry Direction ◽

Exotic States ◽

Ab Initio Simulations ◽

Transition Metal Sulfide ◽

Dirac Materials ◽

Weyl Semimetals

Dirac fermions play a central role in the study of topological phases, for they can generate a variety of exotic states, such as Weyl semimetals and topological insulators. The control and manipulation of Dirac fermions constitute a fundamental step toward the realization of novel concepts of electronic devices and quantum computation. By means of Angle-Resolved Photo-Emission Spectroscopy (ARPES) experiments and ab initio simulations, here, we show that Dirac states can be effectively tuned by doping a transition metal sulfide, BaNiS2, through Co/Ni substitution. The symmetry and chemical characteristics of this material, combined with the modification of the charge-transfer gap of BaCo1−xNixS2 across its phase diagram, lead to the formation of Dirac lines, whose position in k-space can be displaced along the Γ−M symmetry direction and their form reshaped. Not only does the doping x tailor the location and shape of the Dirac bands, but it also controls the metal-insulator transition in the same compound, making BaCo1−xNixS2 a model system to functionalize Dirac materials by varying the strength of electron correlations.

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TiO2 Nanowires as a Wide Bandgap Dirac Material: a numerical study of impurity scattering and Anderson disorder

MRS Proceedings ◽

10.1557/opl.2014.150 ◽

2014 ◽

Vol 1659 ◽

pp. 187-191

Author(s):

Gabriele Penazzi ◽

Peter Deák ◽

Bálint Aradi ◽

Tim Wehling ◽

Alessio Gagliardi ◽

...

Keyword(s):

Band Gap ◽

Numerical Study ◽

Impurity Scattering ◽

Wide Band ◽

Dirac Fermions ◽

Tio2 Nanowires ◽

Wide Band Gap ◽

Substitutional Impurity ◽

Crucial Difference ◽

Dirac Materials

ABSTRACTDirac materials are characterized by exceptional mobility, orders of magnitude higher than any semiconductor, due to the massless pseudorelativistic nature of the Dirac fermions. These systems being semimetallic, the lack of a genuine band-gap poses a serious limitation to their possible applications in electronics. We recently demonstrated that thin TiO2 nanowires can exhibit 1D Dirac states similar to metallic carbon nanotubes, with the crucial difference that these states lie inside the conduction band in proximity of a wide band gap. We analyze the robustness of the Dirac states respect to an Anderson disorder model and substitutional impurity and compare to different one dimensional systems. The results suggest that thin anatase TiO2 nanowires can be a promising candidate material for switching devices.

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Xenon-1T excess as a possible signal of a sub-GeV hidden sector dark matter

Journal of High Energy Physics ◽

10.1007/jhep02(2021)229 ◽

2021 ◽

Vol 2021 (2) ◽

Author(s):

Amin Aboubrahim ◽

Michael Klasen ◽

Pran Nath

Keyword(s):

Dark Matter ◽

Particle Physics ◽

Small Mass ◽

Big Bang ◽

Mass Splitting ◽

Recoil Energy ◽

Dirac Fermions ◽

Dark Sector ◽

Dark Photon ◽

Physics Model

Abstract We present a particle physics model to explain the observed enhancement in the Xenon-1T data at an electron recoil energy of 2.5 keV. The model is based on a U(1) extension of the Standard Model where the dark sector consists of two essentially mass degenerate Dirac fermions in the sub-GeV region with a small mass splitting interacting with a dark photon. The dark photon is unstable and decays before the big bang nucleosynthesis, which leads to the dark matter constituted of two essentially mass degenerate Dirac fermions. The Xenon-1T excess is computed via the inelastic exothermic scattering of the heavier dark fermion from a bound electron in xenon to the lighter dark fermion producing the observed excess events in the recoil electron energy. The model can be tested with further data from Xenon-1T and in future experiments such as SuperCDMS.

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Dirac node engineering and flat bands in doped Dirac materials

Physical Review Research ◽

10.1103/physrevresearch.3.033001 ◽

2021 ◽

Vol 3 (3) ◽

Author(s):

Anna Pertsova ◽

Peter Johnson ◽

Daniel P. Arovas ◽

Alexander V. Balatsky

Keyword(s):

Flat Bands ◽

Dirac Materials

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Half-Dirac Semimetal and Quantum Anomalous Hall Effect in Kagome Cd2N3 Lattice

Nanoscale Advances ◽

10.1039/d0na00530d ◽

2020 ◽

Author(s):

Xinyang Li ◽

Weixiao Ji ◽

Peiji Wang ◽

Chang-wen Zhang

Keyword(s):

Hall Effect ◽

Quantum State ◽

Anomalous Hall Effect ◽

Topological Phases ◽

Dirac Semimetal ◽

Quantum Anomalous Hall Effect ◽

Dirac Materials ◽

Low Dimensionality ◽

Dirac Semimetals ◽

Topological Phases Of Matter

Half-Dirac semimetals (HDSs), which possess 100% spin-polarizations for Dirac materials, are highly desirable for exploring various topological phases of matter, as low-dimensionality opens unprecedented opportunities for manipulating the quantum state...

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Electrical confinement in a spectrum of two-dimensional Dirac materials with classically integrable, mixed, and chaotic dynamics

Physical Review Research ◽

10.1103/physrevresearch.2.013116 ◽

2020 ◽

Vol 2 (1) ◽

Cited By ~ 3

Author(s):

Chen-Di Han ◽

Hong-Ya Xu ◽

Ying-Cheng Lai

Keyword(s):

Chaotic Dynamics ◽

Two Dimensional ◽

Dirac Materials

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High-frequency rectifiers based on type-II Dirac fermions

Nature Communications ◽

10.1038/s41467-021-21906-w ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Libo Zhang ◽

Zhiqingzi Chen ◽

Kaixuan Zhang ◽

Lin Wang ◽

Huang Xu ◽

...

Keyword(s):

High Frequency ◽

Dynamic Range ◽

High Sensitivity ◽

High Dynamic Range ◽

Anisotropy Ratio ◽

Dirac Fermions ◽

Topological States ◽

Topological Semimetals ◽

Polarized Surface ◽

Symmetry Protected

AbstractThe advent of topological semimetals enables the exploitation of symmetry-protected topological phenomena and quantized transport. Here, we present homogeneous rectifiers, converting high-frequency electromagnetic energy into direct current, based on low-energy Dirac fermions of topological semimetal-NiTe2, with state-of-the-art efficiency already in the first implementation. Explicitly, these devices display room-temperature photosensitivity as high as 251 mA W−1 at 0.3 THz in an unbiased mode, with a photocurrent anisotropy ratio of 22, originating from the interplay between the spin-polarized surface and bulk states. Device performances in terms of broadband operation, high dynamic range, as well as their high sensitivity, validate the immense potential and unique advantages associated to the control of nonequilibrium gapless topological states via built-in electric field, electromagnetic polarization and symmetry breaking in topological semimetals. These findings pave the way for the exploitation of topological phase of matter for high-frequency operations in polarization-sensitive sensing, communications and imaging.

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