Andreev Edge State on Semi-Infinite Triangular Lattice: Detecting the Pairing Symmetry in Na_0.35CoO_2.yH_2O

TL;DR

This paper investigates Andreev edge states on a semi-infinite triangular lattice to identify pairing symmetries in Na_xCoO_2 using Fourier-transformed scanning tunneling spectroscopy, revealing a complex phase diagram.

Contribution

It introduces a comprehensive analysis of Andreev edge states for various pairing symmetries on a triangular lattice and proposes a method to determine pairing symmetry in Na_xCoO_2.

Findings

Rich phase diagram of zero energy Andreev edge states for different pairing symmetries

Proposed Fourier-transformed scanning tunneling spectroscopy as a detection method

Explanation of phase diagram via gauge argument and 1D tight-binding model

Abstract

We study the Andreev edge state on the semi-infinite triangular lattice with different pairing symmetries and boundary topologies. We find a rich phase diagram of zero energy Andreev edge states that is a unique fingerprint of each of the possible pairing symmetries. We propose to pin down the pairing symmetry in recently discovered Na_xCoO_2 material by the Fourier-transformed scanning tunneling spectroscopy for the edge state. A surprisingly rich phase diagram is found and explained by a general gauge argument and mapping to 1D tight-binding model. Extensions of this work are discussed at the end.