Experimental realization of two-dimensional weak topological insulators

Abstract

We report the experimental realization of two-dimensional (2D) weak topological insulator (WTI) in spinless Su-Schrieffer-Heeger circuits with parity-time and chiral symmetries. Strong and weak ${\mathbb{Z}}_2$ topological indexes are adopted to explain the experimental findings that a Dirac semimetal (DSM) phase and four WTI phases emerge in turn when we modulate the centrosymmetric circuit deformations. In DSM phase, it is found that the Dirac cone is highly anisotropic and not pinned to any high-symmetry points but can widely move within the Brillouin zone, which eventually leads to the phase transition between WTIs. In addition, we observe a pair of flat-band domain wall states by designing spatially inhomogeneous node connections. Our work provides the first experimental evidence for 2D WTIs, which significantly advances our understanding on the strong and weak nature of topological insulators, the robustness of flat bands, and the itinerant and anisotropic feature of Dirac cones.

References in corpus (18)

• Quantum Spin Hall Effect and Topological Phase Transition in HgTe Quantum Wells
• Quantum Spin Hall Insulator State in HgTe Quantum Wells
• Topological Insulators with Inversion Symmetry
• Discovery (theoretical prediction and experimental observation) of a large-gap topological-insulator class with spin-polarized single-Dirac-cone on the surface
• A topological Dirac insulator in a quantum spin Hall phase : Experimental observation of first strong topological insulator
• Three dimensional topological invariants for time reversal invariant Hamiltonians and the three dimensional quantum spin Hall effect
• Observation of a localized flat-band state in a photonic Lieb lattice
• Observation of bound states in Lieb photonic lattices
• Topological properties of linear circuit lattices
• Stacked topological insulator built from bismuth-based graphene sheet analogues
• Gain and loss induced topological insulating phase in a non Hermitian electrical circuit
• Topolectrical-circuit octupole insulator with topologically protected corner states
• Anderson localisation in tight-binding models with flat bands
• Prediction of weak topological insulators in layered semiconductors
• Majorana-like zero modes in Kekulé distorted sonic lattices
• Observation and control of the weak topological insulator state in ZrTe5
• Chiral anomaly of Weyl magnons in stacked honeycomb ferromagnets
• Observation of symmetry protected zero modes in topolectrical circuits