Negative magnetoresistance in the antiferromagnetic semimetal V_(1/3)TaS_(2)

Intercalated transition metal dichalcogenides(TMDCs)attract much attention due to their rich properties and potential applications.In this article,we grew successfully high-quality V_(1/3)TaS_(2) crystals by a vapor transport method.We measured the magnetization,longitudinal resistivityρxx(T,H),Hall resistivityρxy(T,H),as well as performed calculations of the electronic band structure.It was found that V_(1/3)TaS_(2) is an A-type antiferromagnet with the Neel temperature T_(N)=6.20 K,and exhibits a negative magnetoresistance(MR)near T_(N).Both band structure calculations and Hall resistivity measurements demonstrated it is a magnetic semimetal.

Literature classification and its applications in condensed matter physics and materials science by natural language processing

The exponential growth of literature is constraining researchers’access to comprehensive information in related fields.While natural language processing(NLP)may offer an effective solution to literature classification,it remains hindered by the lack of labelled dataset.In this article,we introduce a novel method for generating literature classification models through semi-supervised learning,which can generate labelled dataset iteratively with limited human input.We apply this method to train NLP models for classifying literatures related to several research directions,i.e.,battery,superconductor,topological material,and artificial intelligence(AI)in materials science.The trained NLP‘battery’model applied on a larger dataset different from the training and testing dataset can achieve F1 score of 0.738,which indicates the accuracy and reliability of this scheme.Furthermore,our approach demonstrates that even with insufficient data,the not-well-trained model in the first few cycles can identify the relationships among different research fields and facilitate the discovery and understanding of interdisciplinary directions.

Excitonic Instability in Ta2Pd3Te5 Monolayer

By systematic theoretical calculations,we reveal an excitonic insulator(EI)in the Ta_(2)Pd_(3)Te_(5)monolayer.The bulk Ta_(2)Pd_(3)Te_(5)is a van der Waals(vdW)layered compound,whereas the vdW layer can be obtained through exfoliation or molecular-beam epitaxy.First-principles calculations show that the monolayer is a nearly zero-gap semiconductor with the modified Becke–Johnson functional.Due to the same symmetry of the band-edge states,the two-dimensional polarization 2D would be finite as the band gap goes to zero,allowing for an EI state in the compound.Using the first-principles many-body perturbation theory,the GW plus Bethe–Salpeter equation calculation reveals that the exciton binding energy is larger than the single-particle band gap,indicating the excitonic instability.The computed phonon spectrum suggests that the monolayer is dynamically stable without lattice distortion.Our findings suggest that the Ta_(2)Pd_(3)Te_(5) monolayer is an excitonic insulator without structural distortion.

VASP2KP:k·p Models and Landég-Factors from ab initio Calculations

The k·p method is significant in condensed matter physics for the compact and analytical Hamiltonian.In the presence of magnetic field,it is described by the effective Zeeman's coupling Hamiltonian with Landég-factors.Here,we develop an open-source package VASP2KP(including two parts:vasp2mat and mat2kp)to compute k·p parameters and Landég-factors directly from the wavefunctions provided by the density functional theory(DFT)as implemented in Vienna ab initio Simulation Package(VASP).First,we develop a VASP patch vasp2mat to compute matrix representations of the generalized momentum operatorπ=p+1/2mc^(2)[s×■V(r)],spin operator s,time reversal operatorT,and crystalline symmetry operatorsR on the DFT wavefunctions.Second,we develop a python code mat2kp to obtain the unitary transformation U that rotates the degenerate DFT basis towards the standard basis,and then automatically compute the k·p parameters and g-factors.The theory and the methodology behind VASP2KP are described in detail.The matrix elements of the operators are derived comprehensively and computed correctly within the projector augmented wave method.We apply this package to some materials,e.g.,Bi2Se3,Na3Bi,Te,InAs and 1H-TMD monolayers.The obtained effective model's dispersions are in good agreement with the DFT data around the specific wave vector,and the g-factors are consistent with experimental data.The VASP2KP package is available at https://github.com/zjwang11/VASP2KP.

CsBaB_(3)O_(6):Eu^(3+) red-emitting phosphors for white LED and FED:Crystal structure,electronic structure and luminescent properties

Recently,borate compounds have received much attention in the field of rare earth doped phosphors due to their excellent luminescent performance.In this work,to explore the potential in LED and FED applications,the CsBaB_(3)O_(6):Eu^(3+)phosphor was investigated in detail by using Rietveld refinement,DFT calculations,photoluminescent and cathodoluminescent spectra.As a result,CsBaB_(3)O_(6)has a planar stacked three-dimensional layered structure.Under the excitation of 395 nm n-UV light and electron beam,CsBaB_(3)O_(6):Eu^(3+)phosphor exhibits a typical red emission of Eu^(3+).A good thermal stability and good resistance to saturation and degradation were observed in the CsBaB_(3)O_(6):Eu^(3+)phosphor.The related photoluminescent and cathodoluminescent mechanisms were studied.The results indicate that CsBaB_(3)O_(6):Eu^(3+)phosphor has potential in multifunctional applications.