  Negative differential conductivity (NDC) is a widely exploited effect in
modern electronic components. Here, a proof-of-principle is given for the
observation of NDC in a quantum transport device for neutral atoms employing a
multi-mode tunneling junction. The transport of the many-body quantum system is
governed by the interplay between the tunnel coupling, the interaction energy
and the thermodynamics of intrinsic collisions, which turn the coherent
coupling into a hopping process. The resulting current voltage characteristics
exhibit NDC, for which we identify a new microscopic physical mechanism. Our
study opens new ways for the future implementation and control of complex
neutral atom quantum circuits.
