We present the findings of the 0.7·(2e 2 /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·(2e 2 /h) feature from the e 2 /h to 3/2 e 2 /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·(2e 2 /h) feature is close to the value of 0.5·(2e 2 /h) that indicates the spin degeneracy lifting for the first step of the quantum conductance staircase. The 0.7·(2e 2 /h) feature is found to take however the value of 0.75·(2e 2 /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·(2e 2 /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·(2e 2 /h) feature. Finally, the variations of the 0.7·(2e 2 /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. IntroductionProgress in semiconductor nanotechnology makes it possible to fabricate clean one-dimensional (1D) constrictions with low density of high-mobility charge carriers, which exhibit ballistic behavior if the mean free path is longer than the channel length [1][2][3][4][5][6][7][8]. Therefore, the conductance of such quantum wires prepared by the split-gate [1-7] and cleaved edge overgrowth [8] methods depends only on the transmission coefficient, T [9, 10]:

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We have recently introduced a quantum mechanical polarizable force field (QMPFF) fitted solely to high-level quantum mechanical data for simulations of biomolecular systems. Here, we present an improved form of the force field, QMPFF2, and apply it to simulations of liquid water. The results of the simulations show excellent agreement with a variety of experimental thermodynamic and structural data, as good or better than that provided by specialized water potentials. In particular, QMPFF2 is the only ab initio force field to accurately reproduce the anomalous temperature dependence of water density to our knowledge. The ability of the same force field to successfully simulate the properties of both organic molecules and water suggests it will be useful for simulations of proteins and protein-ligand interactions in the aqueous environment.G eneral-purpose force fields, from Levitt's early protein potential (1) to modern models such as CHARMM, OPLS-AA, MMFF, and AMBER (2-5), which approximate molecular potentials by simple analytical formulas, are in wide use for computational studies of biological systems ranging from the simplest molecular clusters to large complexes involving proteins. In the latter case, the investigations encounter serious computational problems, primarily related to proper conformational sampling and adequate treatment of the long-range intermolecular interactions; however, with advancements in simulation methodologies and the increase in computer speed these difficulties are alleviated so the accuracy of the underlying models becomes the dominant factor.Protein and protein-ligand interactions usually take place in an aqueous environment, which contributes critically to their energetics, e.g., by hydrogen bonding and the hydrophobic effect. Hence, a force field should accurately reproduce the properties of both organic compounds and water if it is to be used for precise calculations of protein-ligand binding, as required for example in drug-design applications. Moreover, the quality of the applications of a force field to water can be considered as a criterion for the accuracy of the approach as a whole. Hence, it is disconcerting that no general-purpose force field has previously succeeded in accurately describing key properties of liquid water.On the other hand, impressive progress has been made in theoretical studies using specialized water potentials. Many of these potentials are empirical, i.e., they have been fitted to experimental data on the thermodynamics and kinetics of liquid water and in some cases ice. The most advanced of these models, such as the pairwise additive TIP5P (6) and polarizable (7-9) potentials, generally provide an accurate description of the most important properties of water and͞or ice. However, no one model is yet able to reproduce in detail the diversity of thermodynamic and kinetic experimental data on both gas and condensed phases under a range of conditions. Moreover, these empirical water potentials cannot be transferred to more general molecular systems ...

The spin-interference that is caused by the Rashba spin-orbit interaction in a gate-controlled Aharonov-Bohm ring is studied by the analysis of the conductance oscillations as a function of both the gate voltage and magnetic field. The scattering matrix approach is used to reveal the effect of the quantum scatterers connected to two one-dimensional leads on the phase of the transmission and reflection amplitudes. The variations of the transmission and reflection amplitudes that are caused by the quantum scatterers for the particles moving inside and outside rings are shown to define a parity of the and conductance oscillations.The spin-correlated transport in low-dimensional systems was in focus of both theoretical and experimental activity in the last decade [1][2][3]. The studies of the spin-orbit interaction (SOI) that results from both the crystal and the structure inversion asymmetry in mesoscopic nanostructures have specifically attracted much of the efforts [4][5][6][7][8][9][10][11][12][13][14][15][16]. The first mechanism called the Dresselhaus SOI gives rise to the energy separation between the spin bands that is proportional to the cube of the particle wave number, [17]. The Dresselhaus SOI becomes dominant in bulk structures, whereas the second mechanism called the Rashba SOI appears to lift the spin degeneracy of the wave vector parallel to the quantum well (QW) thereby leading to the spin splitting at the Fermi energy that is linear on [18]. The Rashba SOI has been found to dominate over the Dresselhaus SOI in the Si- MOSFET [19] as well as in InAs/GaSb, AlSb/InAs and GaAs/GaAlAs heterostructures [9,[13][14][15][16][20][21][22] because of the macroscopic potentials along the interface, which result in the electric field perpendicular to the two-dimensional electron/hole gas.The Rashba SOI parameter α dependent linearly on the external electric field is of importance to be tuned by varying the gate voltage [9,[13][14][15]. These variations of the spin splitting at the Fermi energy cause the spin interference effects that have been revealed by beating in