Transport and noise measurements in long, narrow YbRh₂Si₂ wires

The heavy fermion compound YbRh₂Si₂ exhibits a magnetic field-induced quantum critical point, between an antiferromagnetically ordered phase and a paramagnetic heavy Fermi liquid phase. Although the zero-field magnetic ordering temperature is only 70 mK, quantum critical non-Fermi liquid behavior persists over a broad temperature range, providing a wide parameter space to study the electron correlations in this “strange metal” system. Previous shot noise measurements on short YbRh₂Si₂ nanowires show a strong suppression compared to Fermi liquid metals like gold, and it is important to assess if this is an essential feature of strange metals due to a lack of quasiparticles, or whether strong electron-phonon coupling plays a role. Here we fabricate long, narrow YbRh₂Si₂ wires using the same method as in the short nanowire experiments and infer the electron-phonon energy transfer strength using the noise measurement. The results show the electron-phonon energy transfer strength in YbRh₂Si₂ is comparable with that in a gold device, meaning that the suppression of shot noise in YbRh₂Si₂ nanowires is not due to phonons. Our measurements provide supplemental support for previous work and quantify the energy transfer strength from electron to phonon in YbRh₂Si₂.