Giant spin-orbit splitting of point defect states in monolayer WS2_2

The spin-orbit coupling (SOC) effect has been known to be profound in monolayer pristine transition metal dichalcogenides (TMDs). Here we show that point defects, which are omnipresent in the TMD membranes, exhibit even stronger SOC effects and change the physics of the host materials drastically. In this Article we chose the representative monolayer WS\sub{2} slabs from the TMD family together with seven typical types of point defects including monovacancies, interstitials, and antisites. We calculated the formation energies of these defects, and studied the effect of spin-orbit coupling (SOC) on the corresponding defect states. We found that the S monovacancy (V\sub{S} ) and S interstitial (adatom) have the lowest formation energies. In the case of V\sub{S} and both of the W\sub{S and W\sub{S2} antisites, the defect states exhibit giant splitting up to 296 meV when SOC is considered. Depending on the relative position of the defect state with respect to the conduction band minimum (CBM), the hybrid functional HSE will either increase the splitting by up to 60 meV (far from CBM), or decrease the splitting by up to 57 meV (close to CBM). Furthermore, we found that both the W\sub{S} and W\sub{S2} antisites possess a magnetic moment of 2 $\mu_{B}$ localized at the antisite W atom and the neighboring W atoms. All these findings provide new insights in the defect behavior under SOC point to new possibilities for spintronics applications for TMDs.Comment: 8 pages, 6 figure

Supplier Initiating Risk Management Behaviour and Supply-Side Resilience:The Effects of Interpersonal Relationships and Dependence Asymmetry in Buyer-Supplier Relationships

Purpose The aim of the study is to explore how two dimensions of interpersonal relationships (i.e. size and range of relationships) affect supplier-initiating risk management behaviours (SIRMB) and supply-side resilience. Further, the study aims to explore the moderating role of dependence asymmetry. Design/methodology/approach Nine hypotheses are tested based on a moderated mediation analysis of survey data from 247 manufacturing firms in China. The data are validated using a subset of 57 attentive secondary respondents and archival data. Findings SIRMB positively relates to supply-side resilience. Further, SIRMB mediates the positive relationship between range and supply-side resilience, and this relationship is stronger at lower levels of dependence asymmetry. Yet, although dependence asymmetry positively moderates the relationship between range and SIRMB, it negatively moderates the relationship between size and SIRMB. We did not, however, find evidence that size has a conditional indirect effect on supply-side resilience through SIRMB. Practical implications Managers in buying firms can incentivise SIRMB to enhance supply-side resilience by developing a diverse rather than a large set of interpersonal relationships with a supplier. This might include allocating particular employees with a wide range of contacts within a supplier to that relationship, while it may be necessary to adopt different networking strategies for different supplier relationships. Firms in a highly asymmetrical relationship may seek to raise supplier expectations about the necessity to initiate risk management behaviour or look to change the dynamic of the relationship by managing contracts for fairness. Originality/value New knowledge on SIRMB as a mediating variable underpinning the relationship between interpersonal relationships and supply-side resilience is provided; and empirical evidence on the opposing moderation effect of dependence asymmetry is presented

Millimeter Spectral Line Mapping Observations Toward Four Massive Star Forming HII Regions

We present spectral line mapping observations toward four massive star-forming regions (Cepheus A, DR21S, S76E and G34.26+0.15), with the IRAM 30 meter telescope at 2 mm and 3 mm bands. Totally 396 spectral lines from 51 molecules, one helium recombination line, ten hydrogen recombination lines, and 16 unidentified lines were detected in these four sources. An emission line of nitrosyl cyanide (ONCN, 14$_{0,14}$-13$_{0,13}$) was detected in G34.26+0.15, as first detection in massive star-forming regions. We found that the $c$-C$_{3}$H$_{2}$ and NH$_{2}$D show enhancement in shocked regions as suggested by evidences of SiO and/or SO emission. Column density and rotational temperature of CH$_{3}$CN were estimated with the rotational diagram method for all four sources. Isotope abundance ratios of $^{12}$C/$^{13}$C were derived using HC$_{3}$N and its $^{13}$C isotopologue, which were around 40 in all four massive star-forming regions and slightly lower than the local interstellar value ($\sim$65). $^{14}$N/$^{15}$N and $^{16}$O/$^{18}$O abundance ratios in these sources were also derived using double isotopic method, which were slightly lower than that in local interstellar medium. Except for Cep A, $^{33}$S/$^{34}$S ratio in the other three targets were derived, which were similar to that in the local interstellar medium. The column density ratios of N(DCN)/N(HCN) and N(DCO$^{+}$)/N(HCO$^{+}$) in these sources were more than two orders of magnitude higher than the elemental [D]/[H] ratio, which is 1.5$\times$10$^{-5}$. Our results show the later stage sources, G34.26+0.15 in particular, present more molecular species than earlier stage ones. Evidence of shock activity is seen in all stages studied.Comment: 32 pages, 11 figures, 8 tables, accepted for publication in MNRA

Structure and morphology of X-ray selected AGN hosts at 1<z<3 in CANDELS-COSMOS field

We analyze morphologies of the host galaxies of 35 X-ray selected active galactic nucleus (AGNs) at $z\sim2$ in the Cosmic Evolution Survey (COSMOS) field using Hubble Space Telescope/WFC3 imaging taken from the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS). We build a control sample of 350 galaxies in total, by selecting ten non-active galaxies drawn from the same field with the similar stellar mass and redshift for each AGN host. By performing two dimensional fitting with GALFIT on the surface brightness profile, we find that the distribution of S$\`e$rsic index (n) of AGN hosts does not show a statistical difference from that of the control sample. We measure the nonparametric morphological parameters (the asymmetry index A, the Gini coefficient G, the concentration index C and the M20 index) based on point source subtracted images. All the distributions of these morphological parameters of AGN hosts are consistent with those of the control sample. We finally investigate the fraction of distorted morphologies in both samples by visual classification. Only $\sim$15% of the AGN hosts have highly distorted morphologies, possibly due to a major merger or interaction. We find there is no significant difference in the distortion fractions between the AGN host sample and control sample. We conclude that the morphologies of X-ray selected AGN hosts are similar to those of nonactive galaxies and most AGN activity is not triggered by major merger.Comment: 5 pages, 3 figures, accepted for publication in The Astrophysical Journal Letter