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

Anderson Impurity in Helical Metal

We use a trial wave function to study the spin-1/2 Kondo effect of a helical metal on the surface of a three-dimensional topological insulator. While the impurity spin is quenched by conduction electrons, the spin-spin correlation of the conduction electron and impurity is strongly anisotropic in both spin and spatial spaces. As a result of strong spin-orbit coupling, the out-of-plane component of the impurity spin is found to be fully screened by the orbital angular momentum of the conduction electrons.Comment: The published versio

An Exploration of the Experience of Interaction between the Police and Juvenile Offenders in Taiwan

By developing Foucault’s concepts of power, this paper aims to explore the interaction experience between Taiwanese police and juvenile offenders from a critical perspective. From macro analysis of social discourse to micro daily practice, the study objectives are to examine whether the police act as a mechanism of discourse formation for juvenile offenders, to articulate how the strategies and techniques are enforced or strengthened and to scrutinise how juveniles are disciplined and resisted. The findings reveal that the dual-oppositional discourses are constructed by defining juveniles as either ‘normal’ or ‘deviant’. Through the discipline and inspection techniques used by police, juveniles are forced to fit the image of the ‘normal juvenile’. To maintain a sense of their autonomous self, juveniles choose to resist these stereotypes. The struggle contributes to the criminal discourse reproduction, pushing juveniles into categories of criminal offenders. It is hoped that this paper can offer a framework for analysing and discussing policy in criminology and criminal justice

Does PPP hold for Big Mac price or consumer price index? Evidence from panel cointegration

This paper examines the validity of purchasing power parity (PPP) using CPI and Big Mac prices. The benchmark model, i.e., the OLS method, which does not take nonstationarity into account, rejects the hypothesis of PPP regardless of prices used. We next use the panel cointegration method to consider the nonstationary nature of variables. Estimated results for CPI are mixed. The PPP is rejected when the nominal exchange rate is employed as the dependent variable but is not rejected when the price ratio is used as the dependent variable. By contrast, the PPP is overwhelmingly not rejected when the Big Mac price is used. Last, we remove the production bias and re-examine the same issue by using panel cointegration. The PPP is again decisively rejected when CPI price is used but not for Big Mac price. Accordingly, Big Mac price is more supportive to the validity of PPP than CPI price.Big Mac