Shot noise in a strange metal

Strange metal behavior has been observed in materials ranging from high-temperature superconductors to heavy fermion metals. In conventional metals, current is carried by quasiparticles; although it has been suggested that the quasiparticle concept fails in strange metals, direct experimental evidence is challenging to acquire. Shot noise is the fluctuation in the electrical current that results from the statistical variation in the arrival times of electrons, and the noise contains information about the "granularity" and correlations of moving charges. We measure shot noise in nanowires of the heavy fermion strange metal YbRh2Si2. When compared to conventional metals, shot noise in these nanowires is strongly suppressed. We argue that this suppression cannot be attributed to electron-phonon or electron-electron interactions in a Fermi liquid, suggesting that the current is not carried by well-defined quasiparticles in the strange metal regime we probed. We discuss next steps, including examining the noise in strongly interacting Fermi liquids, to see if interactions modify the expectations familiar from conventional mesoscopic physics.