Antichiral surface states and higher-order topological states based on a modified Haldane model

TL;DR

This paper presents a simplified approach to realize antichiral surface states and higher-order topological states in a single-layer honeycomb lattice, using a modified Haldane model emulation, with verification in acoustic crystals.

Contribution

It introduces a new method to achieve antichiral and higher-order topological states in a more practical, simplified system based on a modified Haldane model within a nodal-line semimetal phase.

Findings

Successfully emulated the modified Haldane model physics in a single-layer honeycomb lattice.

Generated valley higher-order topological partial bandgaps with coexisting hinge and surface states.

Verified multiple topological states through numerical simulations in acoustic crystal platforms.

Abstract

Antichiral surface states, characterized by unidirectional propagation on parallel surfaces, offer unique potential for controlling classical waves. However, their realization typically relies on complex implementations of the two-dimensional modified Haldane model, limiting practical applications. Here, we propose a simplified scheme to realize such states within the nodal-line semimetal phase of a single-layer honeycomb lattice, by emulating the essential physics of the modified Haldane model through an introduced layer degree of freedom. Furthermore, we demonstrate that unequal vertical interlayer couplings can generate valley higher-order topological partial bandgaps, hosting coexisting one-dimensional hinge states and gapped antichiral surface states. We numerically verify these multiple topological states in acoustic crystals, establishing a versatile platform for advanced wave manipulation.