Spin-polarized voltage probes for helical edge state: a model study

Theoretical models of a spin-polarized voltage probe (SPVP) tunnel-coupled to the helical edge states (HES) of a quantum spin Hall system (QSHS) are studied. Our first model of the SPVP comprises $N_{P}$ spin-polarized modes (subprobes), each of which is locally tunnel-coupled to the HES, while the SPVP, as a whole, is subjected to a self-consistency condition ensuring zero average current on the probe. We carry out a numerical analysis which shows that the optimal situation for reading off spin-resolved voltage from the HES depends on the interplay of the probe-edge tunnel-coupling and the number of modes in the probe ($N_P$). We further investigate the stability of our findings by introducing Gaussian fluctuations in {\it{(i)}} the tunnel-coupling between the subprobes and the HES about a chosen average value and {\it{(ii)}} spin-polarization of the subprobes about a chosen direction of the net polarization of SPVP. We also perform a numerical analysis corresponding to the situation where four such SPVPs are implemented in a self-consistent fashion across a ferromagnetic barrier on the HES and demonstrate that this model facilitates the measurements of spin-resolved four-probe voltage drops across the ferromagnetic barrier. As a second model, we employ the edge state of a quantum anomalous Hall state (QAHS) as the SPVP which is tunnel-coupled over an extended region with the HES. A two-dimensional lattice simulation for the quantum transport of the proposed device setup comprising a junction of QSHS and QAHS is considered and a feasibility study of using the edge of the QAHS as an efficient spin-polarized voltage probe is carried out in presence of an optimal strength of the disorder.Comment: 13 pages, 14 figures, Revised lattice simulation with new set of parameter

Microstructural evolution in laser-ablation-deposited Fe-25 at.% Ge thin film

Films with Fe-25 at.% Ge composition are deposited by the process of laser ablation on single crystal NaCl and Cu substrates at room temperature. Both the vapor and liquid droplets generated in this process are quenched on the substrate. The microstructures of the embedded droplets show size as well as composition dependence. The hierarchy of phase evolution from amorphous to body-centered cubic (bcc) DO3 to has been observed as a function of size. Some of the medium-sized droplets also show direct formation of ordered DO19 phase from the starting liquid. The evolution of disordered bcc structure in some of the droplets indicates disorder trapping during liquid to solid transformation. The microstructural evolution is analyzed on the basis of heat transfer mechanisms and continuous growth model in the solidifying droplets

Dynamics and correlations at a quantum phase transition beyond Kibble-Zurek

Kibble-Zurek theory (KZ) stands out as the most robust theory of defect generation in the dynamics of phase transitions. KZ utilizes the structure of equilibrium states away from the transition point to estimate the excitations due to the transition using adiabatic and impulse approximations. Here we show, the actual nonequilibrium dynamics lead to a qualitatively different scenario from KZ, as far correlations between the defects (rather than their densities) are concerned. For a quantum Ising chain, we show, this gives rise to a Gaussian spatial decay in the domain wall (kinks) correlations, while KZ would predict an exponential fall. We propose a simple but general framework on top of KZ, based on the "quantum coarsening" dynamics of local correlators in the supposed impulse regime. We outline how our picture extends to generic interacting situations.Comment: Main draft: 11 pages, 2 figure

Diversity and distribution of wild mushrooms in different forest areas of Bankura district, WB, India

Mushrooms are macroscopic fruit bodies of fungi; one of the most diverse groups of living organisms distributed all over the world. In recent past, they have gained significant scientific attention for their profound nutraceutical potentiality. The objective of the present study was to explore the diversity and ecological distribution of mushrooms in different forest areas of Bankura district. The study area includes intermittent dense forest and flood plains from middle-east to eastern part of Bankura district. However, this area received very little attention from a conservation perspective, and there is no such documentation on mushrooms of this area. The survey was conducted from August 2019 to October 2020 including vivid field surveys in the forest depots. The study has revealed a total of 53 identified mushroom species belonging to 40 genera and 30 families. The study has also identified 25 edible, 18 inedible and 15 medicinally potential mushrooms. The genus Russula and the family Russulaceae dominates the myco-population. The finding shows that this region is rich in macrofungal diversity complicatedly linked to the functioning of the local ecosystem. The present study opens new possibilities regarding the exploration and utilization of wild mushrooms in India

Faktor snage nanostrukturiranog bizmut telurida određen oblicima

Bismuth telluride is a thermoelectric material with high figure of merit, used for cooling applications at room temperature. To investigate the effect of morphology and grain size on transport parameters, nanostructured bismuth telluride has been synthesized under different reaction conditions and characterized by X-ray diffraction, transmission electron microscopy and scanning electron microscopy. From the measurement of electrical conductivity and thermoelectric power, power factor for different samples has been obtained. The results show that the transport parameters are critically influenced by the morphology and dimension of the samples that in turn depend on the condition of synthesis. The experimentally observed variation of electrical conductivity with the change of dimensionality of the samples from 2D to 0D, which is in line with the theoretical prediction made by other workers, is discussed. There is a variation of the power factor of the samples prepared under different conditions of synthesis.Bizmut telurid je termoelektrična tvar s visokom učinkovitošću koja se rabi za hlađenje na sobnim temperaturama. Radi istraživanja učinka oblika i veličine zrna na transportne parametre, sintetizirali smo nanostrukturirani bizmut telurid u različitim uvjetima i ispitivali rentgenskom difrakcijom, te propusnom i pretražnom elektronskom mikroskopijom. Mjerenjem električne vodljivosti i termoelektrične snage niza uzoraka odredili smo faktore snage. Ishodi analize pokazuju da transportni parametri jako ovise o obliku i veličini uzoraka, koji pak ovise o uvjetima njihove sinteze. Raspravljamo o opaženim promjenama električne vodljivosti ovisnim o dimenzionalnosti uzoraka od 2D do 0D i nalazimo sklad s teorijskim predviđanjima drugih autora. Nalazimo promjene faktora snage uzoraka pripremljenih uz različite uvjete sinteze

Formation of a gold-carbon dot nanocomposite with superior catalytic ability for the reduction of aromatic nitro groups in water

We report the synthesis of a gold-carbon dot nanocomposite and its utility as a recyclable catalyst for the reduction of aromatic nitro groups. The presence of carbon dots on gold nanosurfaces enhanced the reduction rate by two-fold