Self-Organised Fractional Quantisation in a Hole Quantum Wire

We have investigated hole transport in one-dimensional quantum wires in strained germanium two-dimensional layers. The ballistic conductance characteristics show the regular quantised plateaux in units of n2e2/h, where n is an integer. Additionally, new quantised levels are formed which correspond to values of n = 1/4 reducing to 1/8 in the presence of a strong parallel magnetic field which lifts the spin degeneracy but does not quantise the wavefunction. A further plateau is observed corresponding to n = 1/32 which does not change in the presence of a parallel magnetic field. These values indicate that the system is behaving as if charge was fractionalised with values e/2 and e/4, possible mechanisms are discussed.