Unconventional Electromechanical Response in Ferrocene-Assisted Gold Atomic Chain.

Atomically thin metallic chains serve as pivotal systems for studying quantum transport, with their conductance strongly linked to the orbital picture. We report an unusual electromechanical response in Au/ferrocene/Au junctions, manifested as tilted "Z"- and "V"-shaped features with more than an order-of-magnitude conductance change upon stretching at cryogenic temperatures, a striking deviation from the flat, decaying, or occasionally increasing profiles typically observed in metallic or molecular junctions. This response emerges during the formation of a ferrocene-assisted atomic gold chain in a mechanically controllable break junction setup, enabled by direct metal-organometallic bonding in the absence of anchoring groups. Density functional calculations reveal that molecular tilting within the chain modulates orbital overlap and transmission spectra, driving the observed conductance evolution. These findings identify metallocene as a distinct class of molecular systems with strong mechanical-electronic coupling, opening pathways to engineer nanoscale devices through the interplay of orbital hybridization and mechanical deformation.