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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on PrAlGe by Materials Project

PrAlGe crystallizes in the tetragonal I4_1md space group. The structure is three-dimensional. there are two inequivalent Pr sites. In the first Pr site, Pr is bonded to six Al and six equivalent Ge atoms to form a mixture of edge and face-sharing PrAl6Ge6 cuboctahedra. There are two shorter (3.27 Å) and four longer (3.29 Å) Pr–Al bond lengths. All Pr–Ge bond lengths are 3.28 Å. In the second Pr site, Pr is bonded to six Al and six equivalent Ge atoms to form a mixture of edge and face-sharing PrAl6Ge6 cuboctahedra. There are two shorter (3.27 Å) and four longer (3.29 Å) Pr–Al bond lengths. All Pr–Ge bond lengths are 3.28 Å. There are four inequivalent Al sites. In the first Al site, Al is bonded in a distorted trigonal planar geometry to six Pr and three equivalent Ge atoms. Both Al–Pr bond lengths are 3.27 Å. There are one shorter (2.46 Å) and two longer (2.48 Å) Al–Ge bond lengths. In the second Al site, Al is bonded in a distorted trigonal planar geometry to six Pr and three equivalent Ge atoms. There are one shorter (2.46 Å) and two longer (2.48 Å) Al–Ge bond lengths. In the third Al site, Al is bonded in a distorted trigonal planar geometry to six Pr and three equivalent Ge atoms. All Al–Pr bond lengths are 3.29 Å. There are one shorter (2.46 Å) and two longer (2.48 Å) Al–Ge bond lengths. In the fourth Al site, Al is bonded in a distorted trigonal planar geometry to six Pr and three equivalent Ge atoms. There are two shorter (3.27 Å) and four longer (3.29 Å) Al–Pr bond lengths. There are one shorter (2.46 Å) and two longer (2.48 Å) Al–Ge bond lengths. Ge is bonded in a distorted trigonal planar geometry to six Pr and three Al atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Observation of Weyl fermions in a magnetic non-centrosymmetric crystal

The absence of inversion symmetry in non-centrosymmetric materials has a fundamental role in the emergence of a vast number of fascinating phenomena, like ferroelectricity, second harmonic generation, and Weyl fermions. The removal of time-reversal symmetry in such systems further extends the variety of observable magneto-electric and topological effects. Here we report the striking topological properties in the non-centrosymmetric spin-orbit magnet PrAlGe by combining spectroscopy and transport measurements. By photoemission spectroscopy below the Curie temperature, we observe topological Fermi arcs that correspond to projected topological charges of ±1 in the surface Brillouin zone. In the bulk, we observe the linear energy-dispersion of the Weyl fermions. We further observe a large anomalous Hall response in our magneto-transport measurements, which is understood to arise from diverging bulk Berry curvature fields associated with the Weyl band structure. These results establish a novel Weyl semimetal phase in magnetic non-centrosymmetric PrAlGe.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Charge dynamics of a noncentrosymmetric magnetic Weyl semimetal

The interplay of topology with magnetism in Weyl semimetals recently arose to a vanguard topic, because of novel physical scenarios with anomalous transport properties. Here, we address the charge dynamics of the noncentrosymmetric and ferromagnetic (T C ~ 15 K) PrAlGe material and discover that it harbours electronic correlations, which are reflected in a sizeable reduction of the Fermi velocity with respect to the bare band value at low temperatures (T). At T < T C , the optical response registers a band reconstruction, which additionally causes a reshuffling of spectral weight, pertinent to the electronic environment of the type-I Weyl fermions and tracing the remarkable anomalous Hall conductivity (AHC). With the support of first-principles calculations, we provide evidence for the intimate relationship between a topological resonance of the absorption spectrum and the progressively enhanced occupation of non-trivial states with large Berry curvatures, a requirement for AHC.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗