Spinless composite fermions in an ultrahigh-quality strained Ge quantum well

We report on an observation of a fractional quantum Hall effect in an ultrahigh-quality two-dimensional hole gas hosted in a strained Ge quantum well. The Hall resistance reveals precisely quantized plateaus and vanishing longitudinal resistance at filling factors ν=2/3,4/3, and 5/3. From the temperature dependence around ν=3/2 we obtain the composite fermion mass of m ≈0.4me, where me is the mass of a free electron. Owing to large Zeeman energy, all observed states are spin polarized and can be described in terms of spinless composite fermions.