Two-dimensional type-II Dirac fermions in layered oxides

Abstract

Relativistic massless Dirac fermions can be probed with high-energy physics experiments, but appear also as low-energy quasi-particle excitations in electronic band structures. In condensed matter systems, their massless nature can be protected by crystal symmetries. Classification of such symmetry-protected relativistic band degeneracies has been fruitful, although many of the predicted quasi-particles still await their experimental discovery. Here we reveal, using angle-resolved photoemission spectroscopy, the existence of two-dimensional type-II Dirac fermions in the high-temperature superconductor La${}_{1.77}$Sr${}_{0.23}$CuO${}_4$. The Dirac point, constituting the crossing of $d_{x^2-y^2}$ and $d_{z^2}$ bands, is found approximately one electronvolt below the Fermi level ($E_{\mathrm{F}}$) and is protected by mirror symmetry. If spin-orbit coupling is considered, the Dirac point degeneracy is lifted and the bands acquire a topologically non-trivial character. In certain nickelate systems, band structure calculations suggest that the same type-II Dirac fermions can be realised near $E_{\mathrm{F}}$.

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Cited by in corpus (16)

• Deterministic scheme for two-dimensional type-II Dirac points and experimental realization in acoustics
• Band Structure of Overdoped Cuprate Superconductors: Density Functional Theory Matching Experiments
• Two-dimensional type-II Dirac fermions in a LaAlO3/LaNiO3/LaAlO3 quantum well
• Engineering Dirac states in graphene: Coexisting type-I and type-II Floquet-Dirac fermions
• Type-II topological metals
• Type-II Dirac states in full Heusler compounds XInPd2 (X = Ti, Zr and Hf)
• Strain-Tuned Magnetic Frustration in a Square Lattice $J_1$-$J_2$ Material
• Dispersing and semi-flat bands in the wide band gap two-dimensional semiconductor bilayer silicon oxide
• Realization of a transition between type-I and type-II Dirac semimetals in monolayers
• Correlation-driven electronic nematicity in the Dirac semimetal BaNiS2
• Octupolar edge state in an $e_g$ orbital system on a square lattice
• Two types of superconducting pairs in stripe-ordered La${}_{2-x}$Ba${}_x$CuO${}_4$ ($x=1/8$): evidence from the resistivity measurements
• Flat Surface State with Octupole Moment in an $e_g$ Orbital System on a Simple Cubic Lattice
• Quantum Criticality of Type-I and Critically Tilted Dirac Semimetals
• Effects of Ba doping on the structural and electronic properties of La${}_{2-x}$Ba${}_x$CuO${}_4$
• Origin of the tiny energy gap and Dirac points in monoclinic trilayer nickelate La${}_4$Ni${}_3$O${}_{10}$