PhD and Post Doc Quantum Seminar Series: Mathieu Ouellet

Title: “Shot noise as a probe of correlated materials / Light emission as a probe of electronic pDNrocesses at the nanoscale”

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 quasiparticles are absent in strange metals, direct experimental evidence is challenging to acquire. We measure shot noise to probe the granularity of the current-carrying excitations 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 can be attributed neither to electron-phonon nor to 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.

This work sets the stage for similar studies of other strange metals, to test for universality of this response, and ideally for studies in single devices that may be tuned between Fermi liquid and strange metal regimes. It is also important to consider the noise in strongly interacting Fermi liquids, to see if interactions modify the expectations familiar from conventional mesoscopic physics. Time permitting, I will discuss some recent interesting findings in YbAl3, a mixed valence heavy fermion material.