  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.
