Symmetry-enforced three-dimensional Dirac phononic crystals

Abstract

Dirac semimetals, the materials featured with discrete linearly crossing points (called Dirac points) between four bands, are critical states of topologically distinct phases. Such gapless topological states have been accomplished by a band-inversion mechanism, in which the Dirac points can be annihilated pairwise by perturbations without changing the symmetry of the system. Here, we report an experimental observation of Dirac points that are enforced completely by the crystal symmetry, using a nonsymmorphic three-dimensional phononic crystal. Intriguingly, our Dirac phononic crystal hosts four spiral topological surface states, in which the surface states of opposite helicities intersect gaplessly along certain momentum lines, as confirmed by our further surface measurements. The novel Dirac system may release new opportunities for studying the elusive (pseudo)relativistic physics, and also offer a unique prototype platform for acoustic applications.

References in corpus (23)

• Topological Insulators
• Topological insulators and superconductors
• Electronic Structure of Pyrochlore Iridates: From Topological Dirac Metal to Mott Insulator
• Weyl and Dirac Semimetals in Three Dimensional Solids
• Photonic Floquet Topological Insulators
• Discovery of a Three-dimensional Topological Dirac Semimetal, Na3Bi
• Dirac semimetal and topological phase transitions in A3Bi (A=Na, K, Rb)
• Three Dimensional Dirac Semimetal and Quantum Transports in Cd3As2
• Ultrahigh mobility and giant magnetoresistance in the Dirac semimetal Cd${}_3$As${}_2$
• Observation of a topological 3D Dirac semimetal phase in high-mobility Cd3As2
• Experimental observation of Weyl points
• Observation of a phononic quadrupole topological insulator
• Classification of stable three-dimensional Dirac semimetals with nontrivial topology
• A topological quantum optics interface
• Topological Phase Transition and Texture Inversion in a Tunable Topological Insulator
• Synthetic gauge fields and Weyl point in Time-Reversal Invariant Acoustic Systems
• Three-dimensional topological photonic crystal with a single surface Dirac cone
• Three-Dimensional All-Dielectric Photonic Topological Insulator
• Unexpected mass acquisition of Dirac fermions at the quantum phase transition of a topological insulator
• Topological semimetals with Riemann surface states
• Are the double Fermi arcs of Dirac semimetals topologically protected?
• Observation of Three-dimensional Photonic Dirac points and Spin-polarized Surface Arcs
• Three-dimensional photonic Dirac points stabilized by point group symmetry