Quantum Transport on the Surfaces of Topological Nodal-line Semimetals

TL;DR

This paper derives an analytical surface Green's function for topological nodal-line semimetals and investigates their charge and spin transport properties, revealing distinctive conductance and polarization signatures linked to the material's topological features.

Contribution

It provides the first analytical expression for the surface Green's function of a nodal-line semimetal and explores how surface states influence charge and spin transport in a coupled metallic chain.

Findings

Charge conductance shows a robust plateau at e^2/h or multiple valleys depending on the nodal loop size.

Spin polarization reaches 100% at the conductance plateau or exhibits multiple peaks near 100%.

Transport signatures can identify topological nodal-line semimetals.

Abstract

Topological nodal-line semimetals are always characterized by the drumhead surface states at the open boundaries. In this paper we first derive an analytical expression for the surface Green's function of a nodal-line semimetal. By making use of this result, we explore the charge and spin transport properties of a metallic chain on the surface of a nodal-line semimetal, as functions of the gate voltage applied on the top of the material. According to the size of the nodal loop, due to the coupling to the surface modes, the charge conductance in the chain is found to show a robust plateau at $e^{2}/h$, or to exhibit multiple valleys at $e^{2}/h$. Correspondingly, the spin polarization of the transmitted current is $100\%$ at the plateau region, or exhibits multiple peaks at nearly $100\%$. This feature can be viewed as a transport signature of the topological nodal-line semimetals.