Coexistence of Diamagnetism and Vanishingly Small Electrical Resistance at Ambient Temperature and Pressure in Nanostructures

The great practical utility has motivated extensive efforts to discover ultra-low resistance electrical conductors and superconductors in ambience. Here we report the observation of vanishingly small electrical resistance at the ambient temperature and pressure conditions in films and pellets of a nanostructured material that is composed of silver particles embedded into a gold matrix. Upon cooling below a sample-specific temperature scale ($T_C$) as high as $286$ K, the film resistance drops below $\sim 2\mu \mathrm{\Omega }$, being limited by measurement uncertainty. The corresponding resistivity ($\sim 10^{-12}$ $\mathrm{\Omega }$.m) is at least four orders of magnitude below that of elemental noble metals, such as gold, silver or copper. Furthermore, the samples become strongly diamagnetic below $T_C$, with volume susceptibilities as low as -0.056. We additionally describe methods to tune $T_C$ to temperatures much higher than room temperature.