Nucleation in binary polymer blends: Effects of adding diblock copolymers

The effects of adding AB diblock copolymers to A/B binary blends on the structure and thermodynamics of critical nuclei are studied using the self-consistent field theory. At a fixed ratio of the amount of the two homopolymers, depending on the degree of polymerization and composition of the diblocks, their addition to the blends can either increase or decrease the nucleation free energy barrier relative to the pure A/B blends. The qualitative trend can be deduced from the shift in the coexistence boundary and the spinodal. The distribution of diblock copolymers in critical nuclei depends on the composition of the diblocks and the quench depth. Near the coexistence, symmetric diblocks exhibit surfactant behavior, being highly concentrated on the interface of the critical nuclei. Near the spinodal, they act more like co-solvent with a relatively uniform distribution

Detect Spinons via Spin Transport

Existence of spinons is the defining property of quantum spin liquids. These exotic excitations have (fractionalized) spin quantum number and no electric charge, and have been proposed to form Fermi surfaces in the recently discovered organic spin liquid candidates. However direct probes for them are still lacking. In this paper we propose to experimentally identify the spinons by measuring the spin current flowing through the spin liquid candidate materials, which would be a direct test for the existence of spin-carrying mobile excitations. By the nonequilibrium Green function technique we evaluate the spin current through the interface between a Mott insulator and a metal under a spin bias, and find that different kinds of Mott insulators, including quantum spin liquids, can be distinguished by different relations between the spin bias and spin current, In the end we will also discuss relations to experiments and estimate experimentally relevant parameters.Comment: 7 pages with appendix, 3 figure

Disorder and metal-insulator transitions in Weyl semimetals

The Weyl semimetal (WSM) is a newly proposed quantum state of matter. It has Weyl nodes in bulk excitations and Fermi arcs surface states. We study the effects of disorder and localization in WSMs and find three exotic phase transitions. (I) Two Weyl nodes near the Brillouin zone boundary can be annihilated pairwise by disorder scattering, resulting in the opening of a topologically nontrivial gap and a transition from a WSM to a three-dimensional (3D) quantum anomalous Hall state. (II) When the two Weyl nodes are well separated in momentum space, the emergent bulk extended states can give rise to a direct transition from a WSM to a 3D diffusive anomalous Hall metal. (III) Two Weyl nodes can emerge near the zone center when an insulating gap closes with increasing disorder, enabling a direct transition from a normal band insulator to a WSM. We determine the phase diagram by numerically computing the localization length and the Hall conductivity, and propose that the exotic phase transitions can be realized on a photonic lattice.Comment: 7 pages with appendix, 6 figure

The Impact Mechanism of Charismatic Leadership on Individual\u27s Tacit Knowledge Sharing

Drawing upon charismatic leadership and intrinsic motivation theory, we developed a theoretical model to examine the impact mechanism of charismatic leadership on employees’ tacit knowledge sharing intention in a temporary Enterprise Systems learning team. We conducted a survey-based field study to examine the theoretical model and hypotheses. A total of 153 questionnaires were distributed to ERP users of more than 20 subsidiaries of Beidahuang Group in China and 117 valid questionnaires were returned. Results from structural equation modelling analysis suggest that leader charisma has strong influence on psychological safety climate, which in turn has positive impact on individual’s intrinsic motivation and their tacit knowledge sharing intention. Our results unpack the impact mechanism of leader charisma on individual’s knowledge sharing behaviors, and provide guidelines for the team leader to exhibit appropriate leadership traits in order to promote a psychological safety climate and facilitate an effective knowledge sharing of Enterprise Systems