# Anomalous thermal transport behavior in graphene-like carbon nitride (C$_3$N)

## TL;DR

This study investigates the unusual thermal transport behavior of monolayer C3N, revealing its anomalous temperature dependence and strain response, and elucidates the electronic interactions responsible for these properties, advancing understanding of phonon transport in 2D materials.

## Contribution

It provides the first comprehensive analysis of thermal transport in C3N, highlighting its unique temperature dependence and strain effects, and uncovers the electronic origins of these anomalies.

## Key findings

- C3N exhibits an anomalous temperature dependence of thermal conductivity.
- Applying tensile strain increases C3N's thermal conductivity, unlike graphene.
- Electronic interactions between lone-pair N-s electrons and bonding electrons explain the anomalies.

## Abstract

New classes 2D carbon-based materials beyond graphene have been intensively studied for their promising applications in nano-/opto-/spin-electronics, catalysis, sensors, clean energy, etc. Very recently, the controllable large-scale synthesis of 2D single crystalline carbon nitride (C3N) was reported, which is the first and the only crystalline, hole-free, single-layer carbon nitride with fascinating properties. Herein, we perform a comparative study of thermal transport between monolayer C3N and the parent graphene. The thermal conductivity (k) of C3N shows an anomalous temperature dependence, which is totally different from that for common crystalline materials and deviates largely from the well-known k~1/T relationship. Moreover, the k of C3N is found in surprise to be enlarged by applying bilateral tensile strain, despite its similar planar honeycomb structure as graphene, whose k is reduced upon stretching. The underlying mechanism is revealed by providing direct evidence for the interaction between lone-pair N-s electrons and bonding electrons from C atoms in C3N based on the analysis of orbital-projected electronic structures and electron localization function (ELF). Our study not only make a comprehensive investigation of the thermal transport in graphene-like C3N, but also reveals the physical origins for its anomalous properties, which deepens the understanding of phonon transport in 2D materials.