SEARCH · Engineering Papers

Results for “NaCd4As3”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

2 records

All sources NASA NTRS DOE OSTI

DOE OSTI2020

Materials Data on NaCd4As3 by Materials Project

NaCd4As3 crystallizes in the trigonal R-3m space group. The structure is three-dimensional. Na1+ is bonded to six equivalent As3- atoms to form NaAs6 octahedra that share corners with twelve CdAs4 tetrahedra, edges with six equivalent NaAs6 octahedra, and edges with six equivalent CdAs4 tetrahedra. All Na–As bond lengths are 3.19 Å. There are two inequivalent Cd2+ sites. In the first Cd2+ site, Cd2+ is bonded to four As3- atoms to form distorted CdAs4 tetrahedra that share corners with three equivalent NaAs6 octahedra, corners with ten CdAs4 tetrahedra, edges with three equivalent NaAs6 octahedra, and edges with three equivalent CdAs4 tetrahedra. The corner-sharing octahedral tilt angles are 21°. There are three shorter (2.70 Å) and one longer (3.26 Å) Cd–As bond lengths. In the second Cd2+ site, Cd2+ is bonded to four As3- atoms to form CdAs4 tetrahedra that share corners with three equivalent NaAs6 octahedra, corners with twelve CdAs4 tetrahedra, and edges with six CdAs4 tetrahedra. The corner-sharing octahedral tilt angles are 55°. There are one shorter (2.71 Å) and three longer (2.87 Å) Cd–As bond lengths. There are two inequivalent As3- sites. In the first As3- site, As3- is bonded to three equivalent Na1+ and four Cd2+ atoms to form a mixture of distorted edge and corner-sharing AsNa3Cd4 pentagonal bipyramids. In the second As3- site, As3- is bonded in a distorted body-centered cubic geometry to eight Cd2+ atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2025

Non-equilibrium states and interactions in the topological insulator and topological crystalline insulator phases of NaCd4As3

Topological materials are of great interest because they can support metallic edge or surface states that are robust against perturbations, with the potential for technological applications. Here, we experimentally explore the light-induced non-equilibrium properties of two distinct topological phases in NaCd4As3: a topological crystalline insulator (TCI) phase and a topological insulator (TI) phase. This material has surface states that are protected by mirror symmetry in the TCI phase at room temperature, while it undergoes a structural phase transition to a TI phase below 200 K. After exciting the TI phase by an ultrafast laser pulse, we observe a leading band edge shift of >150 meV that slowly builds up and reaches a maximum after ∼0.6 ps and that persists for ∼8 ps. The slow rise time of the excited electron population and electron temperature suggests that the electronic and structural orders are strongly coupled in this TI phase. It also suggests that the directly excited electronic states and the probed electronic states are weakly coupled. Both couplings are likely due to a partial relaxation of the lattice distortion, which is known to be associated with the TI phase. In contrast, no distinct excited state is observed in the TCI phase immediately or after photoexcitation, which we attribute to the low density of states and phase space available near the Fermi level. Our results show how ultrafast laser excitation can reveal the distinct excited states and interactions in phase-rich topological materials.

Angle-resolved photoemission spectroscopy↗