YbRh₂Si₂ nanodevices: fabrication and measurements

Below 70mK, YbRh₂Si₂, a heavy fermion compound, lies close to a magnetic field-tuned quantum critical point, between an antiferromagnetically ordered Fermi liquid phase and a paramagnetic Fermi liquid phase. This transition can be tuned via magnetic field along the c-axis. Although the zero field magnetic ordering temperature is very low, the non-Fermi liquid regime of quantum criticality persists over a broad temperature range. The understanding of electron transport and correlations in this non-Fermi liquid phase is comparatively unexplored. Here we present a process to fabricate YbRh₂Si₂ nanodevices using a SF₆ dry etch, in which chromium hard masks are used to cover the designed pattern, and then removed by hydrochloric acid. The qualities of etched nanodevices are examined by measuring magnetoresistance and comparing with the unpatterned original film. We plan to study the electron correlations through measuring the shot noise in nanoscale constrictions, in both Fermi liquid and non-Fermi liquid regimes . We will also study the electronic phase coherence by measuring time dependent universal conductance fluctuations.