Spinless composite fermions in an ultra-high quality strained Ge quantum well

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We report on an observation of a fractional quantum Hall effect in an ultra-high 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.