Odd-even phonon transport effects in strained carbon atomic chains bridging graphene nanoribbon electrodes

TL;DR

This study investigates how tensile strain affects phonon transport in finite monatomic carbon chains connected to graphene nanoribbons, revealing odd-even effects linked to bond-length configurations and phonon mode shifts.

Contribution

It uncovers the strain-dependent odd-even phonon transport effects in carbon chains, highlighting the role of bond-length configurations and phonon mode shifts in thermal conductance.

Findings

Odd-numbered chains show decreasing conductance with strain.

Even-numbered chains exhibit increasing conductance with strain.

Strain induces redshifts in longitudinal acoustic phonon modes.

Abstract

Based on first-principles approaches, we study the ballistic phonon transport properties of finite monatomic carbon chains stretched between graphene nanoribbons, an $sp$-$sp^2$ hybrid carbon nanostructure that has recently seen significant experimental advances in its synthesis. We find that the lattice thermal conductance anomalously increases with tensile strain for the even-numbered carbon chains that adopt the alternating bond-length polyyne configuration. On the other hand, in the odd-numbered carbon chain cases, which assume the equal bond-length cumulene configuration, phonon conductance decreases with increasing strain. We show that the strong odd-even phonon transport effects originate from the characteristic longitudinal acoustic phonon modes of carbon wires and their unique strain-induced redshifts with respect to graphene nanoribbon phonon modes. The novel phonon transport properties and their atomistic mechanisms revealed in this work will provide valuable guidelines in de-signing hybrid carbon nanostructures for next-generation electronic, bio, and energy device applications.