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Subject: Fermi level × WGL Institute: IFWD ×

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    Modeling of the properties of the semiconductor solid solution Lu1-xVxNiSb in the presence of magnetic ordering; [Моделювання властивостей напівпровідникового твердого розчину Lu1-xVxNiSb за наявності магнітного упорядкування]
    (Ivano-Frankivsʹk : Fizyko-chimičnyj instytut DVNZ "Prykarpatsʹkyj nacionalʹnyj universytet imeni Vasylja Stefanyka", 2023) Romaka, V.V.; Romaka, V.A.; Stadnyk, Yu.; Romaka, L.; Horyn, A.; Pashkevych, V.; Haraniuk, P.
    Modeling of the thermodynamic, structural, energetic and magnetic properties of the semiconductor solid solution Lu1-xVxNiSb was carried out under the condition of the presence of a magnetic moment on the V atoms and the occurrence of spontaneous magnetization. It is shown that the change in the unit cell parameter a(x) and the mixing enthalpy ΔHmix(х) depends little on the presence or absence of spontaneous magnetization. Modeling of the distribution of the density of electronic states DOS in the presence of a magnetic moment on V atoms revealed the splitting of energy states with spins up and down while preserving the band gap εg of Lu1-xVxNiSb. The relationship between the concentration of magnetic V atoms in Lu1-xVxNiSb and the Curie temperature ТС, when spontaneous magnetization is destroyed and the substance becomes paramagnetic, is established. The solid solution semiconductor Lu1-xVxNiSb, provided spontaneous magnetization is present, can be considered as a promising magnetocaloric.
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    Comprehensive scan for nonmagnetic Weyl semimetals with nonlinear optical response
    (London : Nature Publishing Group, 2020) Xu, Q.; Zhang, Y.; Koepernik, K.; Shi, W.; van den Brink, J.; Felser, C.; Sun, Y.
    First-principles calculations have recently been used to develop comprehensive databases of nonmagnetic topological materials that are protected by time-reversal or crystalline symmetry. However, owing to the low symmetry requirement of Weyl points, a symmetry-based approach to identifying topological states cannot be applied to Weyl semimetals (WSMs). To date, WSMs with Weyl points in arbitrary positions are absent from the well-known databases. In this work, we develop an efficient algorithm to search for Weyl points automatically and establish a database of nonmagnetic WSMs with Weyl points near the Fermi level based on the experimental non-centrosymmetric crystal structures in the Inorganic Crystal Structure Database (ICSD). In total, 46 Weyl semimetals were discovered to have nearly clean Fermi surfaces and Weyl points within 300 meV of the Fermi level. Nine of them are chiral structures which may exhibit the quantized circular photogalvanic effect. In addition, the nonlinear optical response is studied and the giant shift current is explored. Besides nonmagnetic WSMs, our powerful tools can also be used in the discovery of magnetic topological materials.
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    Sixfold fermion near the Fermi level in cubic PtBi2
    (Amsterdam : SciPost Foundation, 2021) Thirupathaiah, Setti; Kushnirenko, Yevhen; Koepernik, Klaus; Piening, Boy Roman; Büchner, Bernd; Aswartham, Saicharan; van den Brink, Jeroen; Borisenko, Sergey; Fulga, Ion Cosma
    We show that the cubic compound PtBi2, is a topological semimetal hosting a sixfold band touching point in close proximity to the Fermi level. Using angle-resolved photoemission spectroscopy, we map the bandstructure of the system, which is in good agreement with results from density functional theory. Further, by employing a low energy effective Hamiltonian valid close to the crossing point, we study the effect of a magnetic field on the sixfold fermion. The latter splits into a total of twenty Weyl cones for a Zeeman field oriented in the diagonal, [111] direction. Our results mark cubic PtBi2, as an ideal candidate to study the transport properties of gapless topological systems beyond Dirac and Weyl semimetals.