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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Evolution of electronic and magnetic properties in the topological semimetal SmSb x Te 2– x

The ZrSiS-type materials have attracted intensive attention due to the existence of various topological fermions. The magnetic version of the ZrSiS-type materials, L n SbTe(L n = lanthanides), is an ideal candidate to explore novel exotic states due to the interaction between magnetism and topology. In this work, we report the experimental study on structural, magnetic, thermodynamic, and electronic properties for SmSb x Te 2– x with various Sb content. Further, the revealed evolutions of these properties with tuning the compositions would provide useful insights for the fundamental topological physics and the future applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

Localized 𝑓-electron magnetism in the semimetal Ce 3 ⁢ Bi 4 ⁢ Au 3

Ce 3 ⁢Bi 4 ⁢ Au 3 crystallizes in the same noncentrosymmetric cubic structure as the prototypical Kondo insulator Ce 3 ⁢ Bi 4 ⁢Pt 3 . Here we report the physical properties of Ce 3 ⁢Bi 4 ⁢ Au 3 single crystals using magnetization, thermodynamic, and electrical-transport measurements. Magnetic-susceptibility and heat-capacity data reveal antiferromagnetic order below 𝑇 𝑁 =3.2K. The magnetic entropy 𝑆 mag reaches 𝑅⁢ ln⁡ 2 slightly above 𝑇 𝑁 , which suggests localized 4⁢𝑓 moments in a doublet ground state. Multiple field-induced magnetic transitions are observed at temperatures below 𝑇 𝑁 , which indicate a complex spin structure with competing interactions. Ce 3 ⁢Bi 4 ⁢ Au 3 shows semimetallic behavior in electrical resistivity in contrast to the majority of reported cerium-based 343 compounds which are semiconducting. Electrical-resistivity measurements under hydrostatic pressure reveal a slight enhancement of 𝑇 𝑁 under pressures up to 2.3 GPa, which supports a scenario wherein Ce 3 ⁢Bi 4 ⁢Au 3 belongs to the far left of the Doniach phase diagram dominated by Ruderman-Kittel-Kasuya-Yosida interactions. Using realistic many-body simulations, we confirm the semimetallic electronic structure of Ce 3 ⁢Bi 4 ⁢ Au 3 and quantitatively reproduce its local moment behavior in the paramagnetic state.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Electronic structure and magnetic and transport properties of antiferromagnetic Weyl semimetal GdAlSi

Here we report the topological electronic structure, magnetic, and magnetotransport properties of a noncentrosymmetric compound GdAlSi. Magnetic susceptibility shows an antiferromagnetic transition at TN = 32 K. In-plane isothermal magnetization exhibits an unusual hysteresis behavior at higher magnetic field, rather than near zero field. Moreover, the hysteresis behavior is asymmetric under positive and negative magnetic fields. First-principles calculations were performed on various magnetic configurations, revealing that the antiferromagnetic state is the ground state, and the spiral antiferromagnetic state is a close competing state. The calculations also reveal that GdAlSi hosts multiple Weyl points near the Fermi energy. The band structure measured by angle-resolved photoemission spectroscopy (ARPES) shows relatively good agreement with the theory, with the possibility of Weyl nodes slightly above the Fermi energy. Within the magnetic ordered state, we observe an exceptionally large anomalous Hall conductivity (AHC) of ~ 1310 Ω-1cm-1 at 2 K. Interestingly, the anomalous Hall effect persists up to room temperature with a significant value of AHC (~ 155 Ω-1cm-1). Our analysis indicates that the large AHC originates from the Berry curvature associated with the multiple pairs of Weyl points near Fermi energy.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Low-energy excitations in type-II Weyl semimetal T d - MoTe 2 evidenced through optical conductivity

Molybdenum ditelluride, MoTe 2 , is a versatile material where the topological phase can be readily tuned by manipulating the associated structural phase transition. The fine details of the band structure of MoTe 2 , key to understanding its topological properties, have proven difficult to disentangle experientially due to the multiband character of the material. Through experimental optical conductivity spectra, we detect two strong low-energy interband transitions. Both are linked to excitations between spin-orbit split bands. The lowest interband transition shows a strong thermal shift, pointing to a chemical potential that dramatically decreases with temperature. Finally, with the help of ab initio calculations and a simple two-band model, we give qualitative and quantitative explanations of the main features in the temperature-dependent optical spectra up to 400 meV.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Identifying the fingerprints of topological states by tuning magnetoresistance in a semimetal: The case of topological half-Heusler Pt 1 - x Au x LuSb

We report that topological materials often exhibit remarkably linear nonsaturating magnetoresistance (LMR), which is both of scientific and technological importance. However, the role of topologically nontrivial states in the emergence of such a behavior has eluded clear demonstration in experiments. Here, by reducing the coupling between the topological surface states (TSS) and the bulk carriers, we controllably tune the LMR behavior in Pt 1-x Au x LuSb into distinct plateaus in Hall resistance, which we show arise from a quantum Hall phase. This allowed us to reveal how smearing of the Landau levels, which otherwise gives rise to a quantum Hall phase, results in an LMR behavior due to strong interaction between the TSS with a positive g factor and the bulk carriers. We establish that controlling the coupling strength between the surface and the bulk carriers in topological materials can bring about dramatic changes in their magnetotransport behavior. In addition, our work outlines a strategy to reveal macroscopic physical observables of TSS in compounds with a semimetallic bulk band structure, as is the case in multifunctional Heusler compounds, thereby opening up opportunities for their utilization in hybrid quantum structures.

36 MATERIALS SCIENCE↗