Angular dependent measurements of the v=5/2 fractional quantum Hall effect state at ultra-low temperatures

The spin polarization of the obscure even-denominator FQHE state at v = (5)/(2) remains an open, but important question to answer. One method to address this question is to measure the angular dependence of its energy gap. Since the energy gap at v = (5)/(2) is rather small, this kind of experiments is technically extraordinary challenging, due to the requirement of in situ rotation of the sample at ultra-low temperatures. We constructed a rotator, made from polycarbonate and operated hydraulically using liquid He-3. A sequence of experiments at v = (5)/(2) clearly demonstrated the possibility of performing angular-dependent measurements at temperatures below 10 mK. (C) 2003 Published by Elsevier Science B.V.