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.

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• Square-root higher-order Weyl semimetals
• Simulation of interaction-induced chiral topological dynamics on a digital quantum computer
• Dirac States in an Inclined Two-Dimensional Su-Schrieffer-Heeger Model
• Observation of Gapped Dirac Cones in a Two-Dimensional Su-Schrieffer-Heeger Lattice
• Competition of non-Hermitian skin effect and topological localization of corner states observed in circuits
• Observation of type-III corner states induced by long-range interactions
• Engineering topological states and quantum-inspired information processing using classical circuits
• Cataloging topological phases of $N$-stacked Su-Schrieffer-Heeger chains by a systematic breaking of symmetries
• Mode-Shell correspondence, a unifying phase space theory in topological physics -- Part I: Chiral number of zero-modes
• Topological aspects in nonlinear optical frequency conversion
• Mode-Shell correspondence, a unifying phase space theory in topological physics -- part II: Higher-dimensional spectral invariants
• Fragile dislocation modes in obstructed atomic topological phases
• Multiple reentrant topological windows induced by generalized Bernoulli disorder