Transport Induced Dimer State from Topological Corner States

TL;DR

This paper explores the transport properties of topological corner states in a second-order topological insulator, revealing how resonant tunneling and dimer state formation can be controlled via an in-plane Zeeman field.

Contribution

It introduces the concept of a dynamic dimer state formed by resonant tunneling of corner states, extending understanding of their transport behavior under Zeeman field tuning.

Findings

Resonant tunneling occurs at specific Zeeman field strengths.

A dimer state can form, extending across the bulk of the flake.

Multiple resonant events are mediated by the same dimer state.

Abstract

Recently, a new type of second-order topological insulator has been theoretically proposed by introducing an in-plane Zeeman field into the Kane-Mele model in the two-dimensional honeycomb lattice. A pair of topological corner states arise at the corners with obtuse angles of an isolated diamond-shaped flake. To probe the corner states, we study their transport properties by attaching two leads to the system. Dressed by incoming electrons, the dynamic corner state is very different from its static counterpart. Resonant tunneling through the dressed corner state can occur by tuning the in-plane Zeeman field. At the resonance, the pair of spatially well separated and highly localized corner states can form a dimer state, whose wavefunction extends almost the entire bulk of the diamond-shaped flake. By varying the Zeeman field strength, multiple resonant tunneling events are mediated by the same dimer state. This re-entrance effect can be understood by a simple model. These findings extend our understanding of dynamic aspects of the second-order topological corner states.