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At least 433 records · Page 24
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Quantifying interfacial energetics of 2D semiconductor electrodes using in situ spectroelectrochemistry and many-body theory

Hot carrier extraction occurs in 2D semiconductor photoelectrochemical cells. Boosting the energy efficiency of hot carrier-based photoelectrochemical cells requires maximizing the hot carrier extraction rate relative to the cooling rate. One could expect to tune the hot carrier extraction rate constant (k ET ) via a Marcus–Gerischer relationship, where k ET depends exponentially on ΔG°' (the standard driving force for interfacial electron transfer). ΔG°' is defined as the energy level difference between a semiconductor's conduction/valence band (CB/VB) minima/maxima and the redox potential of reactant molecules in solution. A major challenge in the electrochemistry community is that conventional approaches to quantify ΔG°' for bulk semiconductors (e.g., Mott–Schottky measurements) cannot be directly applied to ultrathin 2D electrodes. The specific problem is that enormous electronic bandgap changes (>0.5 eV) and CB/VB edge movement take place upon illuminating or applying a potential to a 2D semiconductor electrode. Here, we develop an in situ absorbance spectroscopy approach to quantify interfacial energetics of 2D semiconductor/electrolyte interfaces using a minimal many-body model. Our results show that band edge movement in monolayer MoS 2 is significant (0.2–0.5 eV) over a narrow range of applied potentials (0.2–0.3 V). Such large band edge shifts could change k ET by a factor of 10–100, which has important consequences for practical solar energy conversion applications. We discuss the current experimental and theoretical knowledge gaps that must be addressed to minimize the error in the proposed optical approach.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Magnetic brightening and nanoscale imaging of spin-polarized helical edge modes in ZrTe 5

Efficient charge transport remains a fundamental challenge for nanoelectronic devices, as their performance is constrained by high dissipation and the impedance mismatch between high-frequency signal sources and nanoscale circuit interfaces. Although topologically protected helical edge modes offer a dissipationless and backscattering-resilient alternative, achieving nanoscale control over these modes requires direct visualization of their spatial electrodynamics, especially under high-frequency operation. Here, by utilizing cryogenic magneto-infrared scattering-type scanning near-field optical microscopy (cm-IR-sSNOM), we image spin-polarized helical edge channels in ZrTe 5 at the nanoscale, revealing magnetic-field-induced brightening as a high-frequency electrodynamic signature of robust topological edge modes. Operating at 1.8 K and under a magnetic field of up to 5 T, we observe the emergence of edge-state polarizability at infrared frequencies that is notably resilient to the magnetic gaps that typically quench d.c. and microwave edge transport. Our results reveal a topological ‘two-lane’ spatial reorganization in which an external magnetic field induces a spin-population imbalance between counterpropagating edge modes. Favoured helical branches are confined against physical boundaries to activate a net infrared near-field contrast. This electrodynamic response scales linearly with the number of atomic layers, which confirms that individual layers in ZrTe 5 preserve their discrete quantum spin Hall identities. These findings may be useful for developing topological spintronic devices, as the magnetic infrared tunability of helical edge channels provides a pathway for low-loss nanoscale interconnects and high-speed information processing.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K5Tl3O by Materials Project

K5Tl3O crystallizes in the monoclinic P2_1/m space group. The structure is three-dimensional. there are eight inequivalent K sites. In the first K site, K is bonded in a single-bond geometry to four equivalent Tl and one O atom. There are two shorter (3.80 Å) and two longer (3.95 Å) K–Tl bond lengths. The K–O bond length is 2.69 Å. In the second K site, K is bonded in a single-bond geometry to two Tl and one O atom. Both K–Tl bond lengths are 3.62 Å. The K–O bond length is 2.54 Å. In the third K site, K is bonded in a water-like geometry to two Tl and two equivalent O atoms. Both K–Tl bond lengths are 4.03 Å. There are one shorter (2.83 Å) and one longer (2.86 Å) K–O bond lengths. In the fourth K site, K is bonded in a single-bond geometry to four equivalent Tl and one O atom. There are two shorter (3.80 Å) and two longer (3.95 Å) K–Tl bond lengths. The K–O bond length is 2.69 Å. In the fifth K site, K is bonded in a single-bond geometry to four Tl and one O atom. There are two shorter (3.76 Å) and two longer (3.97 Å) K–Tl bond lengths. The K–O bond length is 2.66 Å. In the sixth K site, K is bonded in a single-bond geometry to four equivalent Tl and one O atom. There are two shorter (3.79 Å) and two longer (3.87 Å) K–Tl bond lengths. The K–O bond length is 2.52 Å. In the seventh K site, K is bonded in a single-bond geometry to four Tl and one O atom. There are two shorter (3.76 Å) and two longer (3.97 Å) K–Tl bond lengths. The K–O bond length is 2.66 Å. In the eighth K site, K is bonded in a single-bond geometry to four equivalent Tl and one O atom. There are two shorter (3.79 Å) and two longer (3.88 Å) K–Tl bond lengths. The K–O bond length is 2.52 Å. There are four inequivalent Tl sites. In the first Tl site, Tl is bonded in a 8-coordinate geometry to six K and two Tl atoms. Both Tl–Tl bond lengths are 3.19 Å. In the second Tl site, Tl is bonded in a 8-coordinate geometry to six K and two Tl atoms. Both Tl–Tl bond lengths are 3.11 Å. In the third Tl site, Tl is bonded in a distorted body-centered cubic geometry to four K and four Tl atoms. In the fourth Tl site, Tl is bonded in a distorted body-centered cubic geometry to four K and four Tl atoms. There are two inequivalent O sites. In the first O site, O is bonded to six K atoms to form edge-sharing OK6 octahedra. In the second O site, O is bonded in an octahedral geometry to six K atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K by Materials Project

K is Copper structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. K is bonded to twelve equivalent K atoms to form a mixture of edge, corner, and face-sharing KK12 cuboctahedra. All K–K bond lengths are 4.71 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Quantum teleportation implies symmetry-protected topological order

We constrain a broad class of teleportation protocols using insights from locality. In the ``standard'' teleportation protocols we consider, all outcome-dependent unitaries are Pauli operators conditioned on linear functions of the measurement outcomes. We find that all such protocols involve preparing a ``resource state'' exhibiting symmetry-protected topological (SPT) order with Abelian protecting symmetry G k = ( Z 2 × Z 2 ) k . The k logical states are teleported between the edges of the chain by measuring the corresponding 2 k string order parameters in the bulk and applying outcome-dependent Paulis. Hence, this single class of nontrivial SPT states is both necessary and sufficient for the standard teleportation of k qubits. We illustrate this result with several examples, including the cluster state, variants thereof, and a nonstabilizer hypergraph state.

Hong, Yifan↗
DOE OSTI2021

Fractional chiral hinge insulator

We propose and study a wave function describing an interacting three-dimensional fractional chiral hinge insulator (FCHI) constructed by Gutzwiller projection of two noninteracting second-order topological insulators with chiral hinge modes at half filling. We use large-scale variational Monte Carlo computations to characterize the model states via the entanglement entropy and charge-spin fluctuations. We show that the FCHI possesses fractional chiral hinge modes characterized by a central charge c = 1 and Luttinger parameter K = 1/2, like the edge modes of a Laughlin 1/2 state. The bulk and surface topology is characterized by the topological entanglement entropy (TEE) correction to the area law. While our computations indicate a vanishing bulk TEE, we show that the gapped surfaces host an unconventional two-dimensional topological phase. In a clear departure from the physics of a Laughlin 1/2 state, we find a TEE per surface compatible with (ln √2 )/2, half that of a Laughlin 1/2 state. This value cannot be obtained from topological quantum field theory for purely two-dimensional systems. For the sake of completeness, we also investigate the topological degeneracy.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Post-growth annealing effects on charge and spin excitations in ND 2-x Ce x CuO 4

We report a Cu K- and L 3 -edge resonant inelastic x-ray scattering study of charge and spin excitations of bulk Nd 2-x Ce x CuO 4 , with focus on post-growth annealing effects. For the parent compound Nd 2 CuO 4 (x = 0), a clear charge-transfer gap is observed in the as-grown state, whereas the charge excitation spectra indicate that electrons are doped in the annealed state. This is consistent with the observation that annealed thin-film and polycrystalline samples of RE 2 CuO 4 (RE = rare earth) can become metallic and superconducting at sufficiently high electron concentrations without Ce doping. For x = 0.16, a Ce concentration for which it is known that oxygen reduction destroys long-range antiferromagnetic order and induces superconductivity, we find that the high-energy spin excitations of non-superconducting as-grown and superconducting annealed crystals are nearly identical. This finding is in stark contrast to the significant changes in the low-energy spin excitations previously observed via neutron scattering

36 MATERIALS SCIENCE↗
DOE OSTI2022

Synthesis and electronic properties of Nd n +1 NinO 3 n +1 Ruddlesden-Popper nickelate thin films

The rare-earth nickelates possess a diverse set of collective phenomena including metal-to-insulator transitions, magnetic phase transitions, and, upon chemical reduction, superconductivity. In this work, we demonstrate epitaxial stabilization of layered nickelates in the Ruddlesden-Popper form, Nd n +1 NinO 3 n +1 , using molecular beam epitaxy. By optimizing the stoichiometry of the parent perovskite NdNiO 3 , we can reproducibly synthesize the n = 1–5 member compounds. X-ray absorption spectroscopy at the O K and Ni L edges indicate systematic changes in both the nickel-oxygen hybridization level and nominal nickel filling from 3$d^8$ to 3$d^7$ as we move across the series from n = 1 to n = ∞. The n = 3 – 5 compounds exhibit weakly hysteretic metal-to-insulator transitions with transition temperatures that depress with increasing order toward NdNiO 3 ( n = ∞).

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K8BiO3 by Materials Project

K8BiO3 crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. K is bonded to one Bi and three equivalent O atoms to form a mixture of distorted corner and edge-sharing KBiO3 tetrahedra. The K–Bi bond length is 3.33 Å. All K–O bond lengths are 3.00 Å. Bi is bonded in a body-centered cubic geometry to eight equivalent K atoms. O is bonded in a body-centered cubic geometry to eight equivalent K atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K3Li by Materials Project

(K)3Li is alpha bismuth trifluoride structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional and consists of four litio molecules and one K framework. In the K framework, there are two inequivalent K sites. In the first K site, K is bonded to four equivalent K atoms to form a mixture of distorted edge and corner-sharing KK4 tetrahedra. All K–K bond lengths are 4.20 Å. In the second K site, K is bonded in a body-centered cubic geometry to eight equivalent K atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K by Materials Project

K is alpha Samarium structured and crystallizes in the trigonal R-3m space group. The structure is three-dimensional. there are five inequivalent K sites. In the first K site, K is bonded to twelve K atoms to form a mixture of distorted face, edge, and corner-sharing KK12 cuboctahedra. There are six shorter (4.63 Å) and six longer (4.79 Å) K–K bond lengths. In the second K site, K is bonded to twelve K atoms to form a mixture of distorted face, edge, and corner-sharing KK12 cuboctahedra. There are three shorter (4.64 Å) and six longer (4.79 Å) K–K bond lengths. In the third K site, K is bonded to twelve K atoms to form a mixture of distorted face, edge, and corner-sharing KK12 cuboctahedra. There are six shorter (4.63 Å) and six longer (4.79 Å) K–K bond lengths. In the fourth K site, K is bonded to twelve K atoms to form a mixture of distorted face, edge, and corner-sharing KK12 cuboctahedra. There are three shorter (4.64 Å) and six longer (4.79 Å) K–K bond lengths. In the fifth K site, K is bonded to sixteen K atoms to form a mixture of distorted face, edge, and corner-sharing KK16 cuboctahedra. There are a spread of K–K bond distances ranging from 4.79–9.58 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K by Materials Project

K is alpha La structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are two inequivalent K sites. In the first K site, K is bonded to twelve K atoms to form a mixture of corner, edge, and face-sharing KK12 cuboctahedra. There are six shorter (4.69 Å) and six longer (4.71 Å) K–K bond lengths. In the second K site, K is bonded to twelve K atoms to form a mixture of corner, edge, and face-sharing KK12 cuboctahedra. All K–K bond lengths are 4.71 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on KRb3 by Materials Project

Rb3K crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. there are two inequivalent Rb sites. In the first Rb site, Rb is bonded in a 12-coordinate geometry to eight Rb atoms. There are four shorter (4.86 Å) and four longer (5.04 Å) Rb–Rb bond lengths. In the second Rb site, Rb is bonded to eight equivalent Rb and four equivalent K atoms to form a mixture of corner, edge, and face-sharing RbK4Rb8 cuboctahedra. All Rb–K bond lengths are 4.86 Å. K is bonded in a square co-planar geometry to four equivalent Rb atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K(Cu2As)2 by Materials Project

K(Cu2As)2 crystallizes in the trigonal R-3m space group. The structure is three-dimensional. K1+ is bonded to six equivalent As3- atoms to form distorted edge-sharing KAs6 octahedra. All K–As bond lengths are 3.37 Å. There are two inequivalent Cu+1.25+ sites. In the first Cu+1.25+ site, Cu+1.25+ is bonded in a 1-coordinate geometry to four equivalent As3- atoms. There are one shorter (2.50 Å) and three longer (2.76 Å) Cu–As bond lengths. In the second Cu+1.25+ site, Cu+1.25+ is bonded in a distorted trigonal non-coplanar geometry to three equivalent As3- atoms. All Cu–As bond lengths are 2.44 Å. As3- is bonded in a 10-coordinate geometry to three equivalent K1+ and seven Cu+1.25+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K(Cu2Sb)2 by Materials Project

K(Cu2Sb)2 crystallizes in the trigonal R-3m space group. The structure is three-dimensional. K1+ is bonded to six equivalent Sb3- atoms to form distorted edge-sharing KSb6 octahedra. All K–Sb bond lengths are 3.50 Å. There are two inequivalent Cu+1.25+ sites. In the first Cu+1.25+ site, Cu+1.25+ is bonded in a 4-coordinate geometry to four equivalent Sb3- atoms. There are one shorter (2.71 Å) and three longer (2.86 Å) Cu–Sb bond lengths. In the second Cu+1.25+ site, Cu+1.25+ is bonded in a trigonal non-coplanar geometry to three equivalent Sb3- atoms. All Cu–Sb bond lengths are 2.60 Å. Sb3- is bonded in a 10-coordinate geometry to three equivalent K1+ and seven Cu+1.25+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K3Mg18Sn11 by Materials Project

K3Mg18Sn11 crystallizes in the hexagonal P6_3/m space group. The structure is three-dimensional. there are two inequivalent K sites. In the first K site, K is bonded in a 12-coordinate geometry to six Mg and six Sn atoms. All K–Mg bond lengths are 3.84 Å. There are three shorter (3.66 Å) and three longer (3.69 Å) K–Sn bond lengths. In the second K site, K is bonded to six equivalent Mg and six equivalent Sn atoms to form distorted KMg6Sn6 cuboctahedra that share corners with eighteen MgSn4 tetrahedra and edges with nine MgK2Sn4 tetrahedra. All K–Mg bond lengths are 3.84 Å. All K–Sn bond lengths are 3.69 Å. There are four inequivalent Mg sites. In the first Mg site, Mg is bonded in a 5-coordinate geometry to five Sn atoms. There are a spread of Mg–Sn bond distances ranging from 2.97–3.09 Å. In the second Mg site, Mg is bonded to four Sn atoms to form distorted MgSn4 tetrahedra that share corners with two equivalent KMg6Sn6 cuboctahedra, corners with eleven MgSn4 tetrahedra, and edges with three MgK2Sn4 tetrahedra. There are a spread of Mg–Sn bond distances ranging from 2.89–3.04 Å. In the third Mg site, Mg is bonded to two equivalent K and four Sn atoms to form distorted MgK2Sn4 tetrahedra that share corners with twelve MgSn4 tetrahedra, an edgeedge with one KMg6Sn6 cuboctahedra, edges with six MgSn4 tetrahedra, and faces with two equivalent MgK2Sn4 tetrahedra. There are a spread of Mg–Sn bond distances ranging from 2.91–2.99 Å. In the fourth Mg site, Mg is bonded to two K and four Sn atoms to form distorted MgK2Sn4 tetrahedra that share a cornercorner with one KMg6Sn6 cuboctahedra, corners with twelve MgSn4 tetrahedra, an edgeedge with one KMg6Sn6 cuboctahedra, edges with six MgSn4 tetrahedra, and faces with two equivalent MgK2Sn4 tetrahedra. There are a spread of Mg–Sn bond distances ranging from 2.94–3.01 Å. There are three inequivalent Sn sites. In the first Sn site, Sn is bonded in a 6-coordinate geometry to six Mg atoms. In the second Sn site, Sn is bonded in a 9-coordinate geometry to two K and seven Mg atoms. In the third Sn site, Sn is bonded in a 9-coordinate geometry to two equivalent K and seven Mg atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K2Hg(CN)4 by Materials Project

K2Hg(CN)4 crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. K1+ is bonded to six equivalent N3- atoms to form distorted edge-sharing KN6 octahedra. All K–N bond lengths are 2.97 Å. Hg2+ is bonded to four equivalent C2+ atoms to form HgC4 tetrahedra that share corners with four equivalent NK3C tetrahedra. All Hg–C bond lengths are 2.21 Å. C2+ is bonded in a single-bond geometry to one Hg2+ and one N3- atom. The C–N bond length is 1.17 Å. N3- is bonded to three equivalent K1+ and one C2+ atom to form distorted NK3C tetrahedra that share a cornercorner with one HgC4 tetrahedra, corners with nine equivalent NK3C tetrahedra, and edges with three equivalent NK3C tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K3Mg18Pb11 by Materials Project

K3Mg18Pb11 crystallizes in the hexagonal P6_3/m space group. The structure is three-dimensional. there are two inequivalent K sites. In the first K site, K is bonded in a 12-coordinate geometry to six Pb atoms. There are three shorter (3.70 Å) and three longer (3.74 Å) K–Pb bond lengths. In the second K site, K is bonded to six equivalent Mg and six equivalent Pb atoms to form distorted KMg6Pb6 cuboctahedra that share corners with eighteen MgPb4 tetrahedra and edges with nine MgPb4 tetrahedra. All K–Mg bond lengths are 3.92 Å. All K–Pb bond lengths are 3.72 Å. There are four inequivalent Mg sites. In the first Mg site, Mg is bonded in a 5-coordinate geometry to five Pb atoms. There are a spread of Mg–Pb bond distances ranging from 3.05–3.19 Å. In the second Mg site, Mg is bonded to four Pb atoms to form distorted MgPb4 tetrahedra that share corners with two equivalent KMg6Pb6 cuboctahedra, corners with eleven MgPb4 tetrahedra, and edges with three MgPb4 tetrahedra. There are a spread of Mg–Pb bond distances ranging from 2.93–3.11 Å. In the third Mg site, Mg is bonded to four Pb atoms to form MgPb4 tetrahedra that share corners with twelve MgPb4 tetrahedra, an edgeedge with one KMg6Pb6 cuboctahedra, and edges with four MgPb4 tetrahedra. There are one shorter (2.95 Å) and three longer (3.03 Å) Mg–Pb bond lengths. In the fourth Mg site, Mg is bonded to one K and four Pb atoms to form distorted MgKPb4 tetrahedra that share a cornercorner with one KMg6Pb6 cuboctahedra, corners with eleven MgPb4 tetrahedra, an edgeedge with one KMg6Pb6 cuboctahedra, and edges with seven MgPb4 tetrahedra. There are a spread of Mg–Pb bond distances ranging from 2.99–3.06 Å. There are three inequivalent Pb sites. In the first Pb site, Pb is bonded in a 6-coordinate geometry to six Mg atoms. In the second Pb site, Pb is bonded in a 9-coordinate geometry to two K and seven Mg atoms. In the third Pb site, Pb is bonded in a 9-coordinate geometry to two equivalent K and seven Mg atoms.

36 MATERIALS SCIENCE↗