Effect of gate voltage on spin transport along α\alpha-helical protein

Recently, the chiral-induced spin selectivity in molecular systems has attracted extensive interest among the scientific communities. Here, we investigate the effect of the gate voltage on spin-selective electron transport through the $\alpha$-helical peptide/protein molecule contacted by two nonmagnetic electrodes. Based on an effective model Hamiltonian and the Landauer-B\"uttiker formula, we calculate the conductance and the spin polarization under an external electric field which is perpendicular to the helix axis of the $\alpha$-helical peptide/protein molecule. Our results indicate that both the magnitude and the direction of the gate field have a significant effect on the conductance and the spin polarization. The spin filtration efficiency can be improved by properly tuning the gate voltage, especially in the case of strong dephasing regime. And the spin polarization increases monotonically with the molecular length without the gate voltage, which is consistent with the recent experiment, and presents oscillating behavior in the presence of the gate voltage. In addition, the spin selectivity is robust against the dephasing, the on-site energy disorder, and the space angle disorder under the gate voltage. Our results could motivate further experimental and theoretical works on the chiral-based spin selectivity in molecular systems.Comment: 8 pages, 7 figure

The impact of mandatory savings on life cycle consumption and portfolio choice

University of Technology Sydney. Faculty of Business.Retirement income systems have increasingly attracted academic research and policy discussion in the light of population aging in developed countries. Management of retirement wealth is of first order importance if sustainable pension systems are to be maintained while providing desirable retirement living standards. In Australia, employers have been compelled by the Superannuation Guarantee to make minimum contributions to retirement accounts on behalf of their employees. Nevertheless, the structure of superannuation is still being discussed and reformed with the aim of making it a better, fairer and more cost-effective system. While there are many empirical studies and policy reviews, research addressing the impact and efficiency of superannuation from a theoretical perspective is lacking. To fill this gap, and to contribute to the wealth management literature, this thesis examines the impact of mandated contributions into superannuation accounts on individuals’ lifetime consumption, risky asset allocation and wealth using a continuous time dynamic life cycle model. First, in Chapter 2, we provide a dynamic model incorporating the compulsory savings constraint for a representative agent. The agent is endowed with deterministic labour income, and assumed to rationally make decisions that maximise his lifetime utility of consumption. Consistent with the primary aim of superannuation, we clearly identify and conclude that compulsory contributions alter the agent’s consumption behaviour and risky investment to be more conservative, which in turn may increase the agent’s total wealth over the life cycle. Building on the model in Chapter 2, we further introduce a life insurance purchase to hedge the mortality risk of the representative agent in Chapter 3. The dynamic model in Chapter 3 is an extension of the work of Pliska and Ye (2007), in which we further consider the forced savings constraint. In addition to the foundational results derived in Chapter 2, we demonstrate a lower bequest value and lower life insurance demand under the compulsory savings constraint. In Chapter 4 we calibrate the theoretical model to the Household, Income and Labour Dynamics in Australia (HILDA) survey data and conduct a range of policy analyses. In particular, we can investigate the welfare loss arising from the one-rate-for-all compulsory contribution rules. Simulations of optimal paths show that the consumption of low-wealth individuals is severely constrained under current settings, resulting in a sizeable welfare loss. In response, we propose a time-varying contribution rate for individuals, which can mitigate the welfare loss while enhancing retirement wealth to achieve a desired retirement living standard

Uniform descriptions of pseudospin symmetries in bound and resonant states

As a continuation of our previous work on the conservation and breaking of the pseudospin symmetry (PSS) in resonant states [Phys. Lett. B 847, 138320 (2023)}], in this work, the PSS in nuclear single-particle bound and resonant states are investigated uniformly within a relativistic framework by exploring the poles of the Green's function in spherical Woods-Saxon potentials. As the potential depths increase from zero to finite depths, the PS partners evolve from resonant states to bound states. In this progress,the PSS is broken gradually with energy, width, and density splittings. Specially, the energy and width splittings for the resonant and bound states are directly determined by the ratio of the pseudo spin-orbit potentials between the PS partners. Obvious threshold effect is observed for the energy splitting at a critical potential depth, with which the PS partners locate between the centrifugal barriers of PS partners. The differences in the density distributions of the lower component between the PS partners are manifested in the phase shift for the resonant states and amplitudes for bound states. Besides, the evolution of the phase shift as the potential depth is consistent with those for the width splitting.Comment: 7 pages, 6 figures. arXiv admin note: substantial text overlap with arXiv:2309.0926