Phase and amplitude response of "0.7 feature" caused by holes in silicon one-dimensional wires and rings

TL;DR

This study investigates the 0.7 feature in hole quantum conductance within silicon quantum wells, revealing its dependence on spin polarization, magnetic field, and spin-orbit interactions, with detailed phase and amplitude responses.

Contribution

It provides new insights into the spin-dependent behavior of the 0.7 conductance feature influenced by Rashba spin-orbit interaction in silicon quantum wires and rings.

Findings

0.7 feature indicates spin polarization at low density

Amplitude and phase of the feature are sensitive to magnetic field and gate voltage

Rashba spin-orbit interaction causes fractional variations in the 0.7 feature

Abstract

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.