Differential Diversity Reception of MDPSK over Independent Rayleigh Channels with Nonidentical Branch Statistics and Asymmetric Fading Spectrum

This paper is concerned with optimum diversity receiver structure and its performance analysis of differential phase shift keying (DPSK) with differential detection over nonselective, independent, nonidentically distributed, Rayleigh fading channels. The fading process in each branch is assumed to have an arbitrary Doppler spectrum with arbitrary Doppler bandwidth, but to have distinct, asymmetric fading power spectral density characteristic. Using 8-DPSK as an example, the average bit error probability (BEP) of the optimum diversity receiver is obtained by calculating the BEP for each of the three individual bits. The BEP results derived are given in exact, explicit, closed-form expressions which show clearly the behavior of the performance as a function of various system parameters.Comment: 5 pages, 3 figures, to present at ISIT200

Chirality-dependent persistent spin current in single circular helix molecules

Since the chiral-induced spin selectivity (CISS) was first observed experimentally, its microscopic mechanism has been continuously explored by the scientific community. Among these investigations, the non-equilibrium effects and the unknown origins of spin-orbit coupling (SOC) have been the central issues discussed in recent years. Here, we have achieved a persistent spin current in different circular single-helix molecule driven by a magnetic field, which is inherently linked to the equilibrium state associated with chirality. Due to its measurement method being different from the transport currents observed in previous experiments, the origin of its spin-orbit coupling can be explored by modifying the substrate with different light and heavy metal elements. Our results demonstrate that a persistent spin current can be observed regardless of whether the SOC originates from the chiral molecule or the substrate. Furthermore, by tuning the direction of the magnetic field, we can achieve a phase transition between trivial and non-trivial chiral persistent spin currents. Our work provides a new perspective and platform for exploring the nature of CISS and controlling the effects of CISS.Comment: 24 pages, 5 figure

Spin-dependent Destructive Quantum Interference Associated with Chirality-induced Spin Selectivity in Circular Single Helix Molecules

Theoretical studies on spin-dependent transport through helical molecules with straight spiral geometry have received intense research interest in the past decade, however, the physics in circular helical molecules has still less been explored. In this work, we theoretically construct a circular single helix (CSH) possessing the chirality-induced spin-orbit coupling and contacting with two non-magnetic electrodes. Our theoretical calculations demonstrate that the spin-related transport in CSH exhibits the so-called chiral-induced spin selectivity (CISS) effect and more importantly, the CISS-reduced spin-dependent destructive quantum interference (DQI) also occurs in the CSH, without any external magnetic field or magnetic electrodes. Moreover, the changing of CSH length or the electrode positions exhibits specific patterns in the spin-polarized conductance. Particularly, the dephasing magnitude can adjust effectively these two spin-dependent effects to realize their coexistence. Additionally, the phase transition between the CISS-dependent constructive quantum interference (CQI) and DQI is also observed in the CSH. Our theoretical work puts forwards a new material plateau to explore the CISS and to exhibit the novel CISS-dependent CQI effect.Comment: 10 pages, 5 figures, 1 tabl