Molecular beam epitaxy growth of nonmagnetic Weyl semimetal LaAlGe thin film
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Research Letter
Molecular beam epitaxy growth of nonmagnetic Weyl semimetal LaAlGe thin film Niraj Bhattarai and Andrew W. Forbes, Department of Physics, The Catholic University of America, Washington, DC 20064, USA; Vitreous State Laboratory, The Catholic University of America, Washington, DC 20064, USA Rajendra P. Dulal, Institute for Quantum Physics, Advanced Physics Laboratory, Chapman University, MD 20866, USA Ian L. Pegg and John Philip, Department of Physics, The Catholic University of America, Washington, DC 20064, USA; Vitreous State Laboratory, The Catholic University of America, Washington, DC 20064, USA Address all correspondence to Niraj Bhattarai at [email protected] (Received 25 January 2020; accepted 15 April 2020)
Abstract Here, the authors report a detailed method of growing LaAlGe, a nonmagnetic Weyl semimetal, thin film on silicon(100) substrates by molecular beam epitaxy and their structural and electrical characterizations. About 50-nm-thick LaAlGe films were deposited and annealed for 16 h in situ at a temperature of 793 K. As-grown high-quality films showed uniform surface topography and near ideal stoichiometry with a body-centered tetragonal crystal structure. Temperature-dependent longitudinal resistivity can be understood with dominant interband s–d electron–phonon scattering in the temperature range of 5–40 K. Hall measurements confirmed the semimetallic nature of the films with an electron-dominated charge carrier density of ∼7.15 × 1021 cm−3 at 5 K.
Introduction The recent theoretical and experimental study has shown that the family of RAlGe (R = La, Ce, and Pr) are Weyl semimetals (WSMs) that offer remarkable tunability including both magnetic and nonmagnetic compounds as well as both type I and type II WSM states.[1–4] WSMs are an exciting class of materials in which the low-energy electronic excitations—massless Weyl fermions—disperse linearly along all three momentum directions through the Weyl nodes. This hallmark feature is observed in the materials’ electronic spectra, precipitating a wide variety of useful properties that hold promise for both fundamental and technological applications such as topological qubits, low-power electronics, and spintronics.[5–7] The origin of WSM behavior in materials lies in breaking crystal inversion symmetry, time-reversal symmetry, or both.[8–10] Breaking at least one of these symmetries can induce unusual physical phenomena, such as spin current without a simultaneous charge current, negative magnetoresistance, Fermi arcs, anomalous quantum Hall effect, and chiral magnetic effects.[11–15] Hence, it is of great interest to enable a wide range of experimental studies on this class of materials, and the first step is to establish the details for the growth of device applicable thin film structures and their structural and electrical characterizations. LaAlGe is a nonmagnetic material relatively understudied compared to its isostructural sister compounds such as CeAlGe and PrAlGe, and there are only a few reports in the literature. Back in 1991, Guloy a
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