  We present the findings of the 0.7(2e2/h) feature in the hole quantum
conductance staircase that is caused by silicon one-dimensional channels
prepared by the split-gate method inside the p-type silicon quantum well (SQW)
on the n-type Si (100) surface. Firstly, the interplay of the spin
depolarisation with the evolution of the 0.7(2e2/h) feature from the e2/h to
3/2 e2/h values as a function of the sheet density of holes is revealed by the
quantum point contact connecting two 2D reservoirs in the p-type SQW. The 1D
holes are demonstrated to be spin-polarised at low sheet density, because the
0.7(2e2/h) feature is close to the value of 0.5(2e2/h) that indicates the spin
degeneracy lifting for the first step of the quantum conductance staircase. The
0.7(2e2/h) feature is found to take however the value of 0.75(2e2/h) when the
sheet density increases thereby giving rise to the spin depolarisation of the
1D holes. Secondly, the amplitude and phase sensitivity of the 0.7(2e2/h)
feature are studied by varying the value of the external magnetic field and the
top gate voltage that are applied perpendicularly to the plane of the
double-slit ring embedded in the p-type SQW, with the extra quantum point
contact inserted in the one of its arms. The Aharonov-Bohm (AB) and the
Aharonov-Casher (AC) conductance oscillations obtained are evidence of the
interplay of the spontaneous spin polarisation and the Rashba spin-orbit
interaction (SOI) in the formation of the 0.7(2e2/h) feature. Finally, the
variations of the 0.7(2e2/h) feature caused by the Rashba SOI are found to take
in the fractional form with both the plateaux and steps as a function of the
top gate voltage.
