Negative Differential Conductance and Hot Phonons in Suspended Nanotube Molecular Wires

Abstract

Freely suspended metallic single-walled carbon nanotubes (SWNTs) exhibit reduced current carrying ability compared to those lying on substrates, and striking negative differential conductance at low electric fields. Theoretical analysis reveals significant self-heating effects including electron scattering by hot nonequilibrium optical phonons. Electron transport characteristics under strong self-heating are exploited for the first time to probe the thermal conductivity of individual SWNTs ($\sim 3600\mathrm{W}{\mathrm{m}}^{-1}{\mathrm{K}}^{-1}$ at $T=300\mathrm{K}$) up to $\sim 700\mathrm{K}$, and reveal a $1/T$ dependence expected for umklapp phonon scattering at high temperatures.