You are here

Highlights

  • Image of the Fermi surface (left) and band dispersion (right) along a red line cut. At 130 K a gapped branch appears that is due to the surface CDW

    Discovery of an unconventional charge density wave (CDW) in purple bronze, a molybdenum oxide, points to a possible new pathway to high temperature superconductivity. A CDW is a state of matter where electrons bunch together periodically, like a standing wave of light or water. CDWs and superconductivity are frenemies, since they share a common origin and often coexist, yet compete for dominance. Conventional CDWs and superconductivity arise from interactions of electrons with lattice vibrations (phonons), while electron-electron interactions are the likely origin of unconventional, high...

    Read More
  • “Ship-in-a-Bottle” synthesis for Pt nanoparticles encapsulated in SiO2 (PtX@mSiO2, X= Sn,Pb,Zn).

    X is introduced by flowing metallic salt into a “bottle”.  mSiO2 is permeable to reactants including furfural and hydrogen.

    For conversion of furfural to alcohol, PtSn yields 100% conversion (2.7x over Pt) and gives 98% selectivity (4.3x over Pt).

    A new “ship-in-a-bottle” approach to making nano-sized intermetallic compound catalysts (materials that increase how fast chemicals can be made) offers more control over stability, activity, product selectivity, and conversion efficiency than possible before.  The approach involves encapsulating the catalyst inside a “glass-bottle” made from porous silica (a.k.a. sand), and the ordered compound self-assembles, forming a designer ship in a bottle.  The development of the new synthesis approach arose by integrating experimental and computational studies to show self-assembly and catalytic...

    Read More
  • The Cu2+ spins (s=1/2 showing by the red allows) fluctuate  even at an ultra-low temperature of 0.02 K, showing a novel quantum spin liquid evidenced by NMR and uSR measurements. 

    Unlike most materials, a newly discovered oxide of lead, copper, and tellurium does not show an orderly arrangement of electron spins near the temperature of “absolute zero” Kelvin (-460 °F).  Approaching “absolute zero”, thermal vibrations slow and typically atoms, and their electron spins, find orderly arrangements resulting in long-range symmetry. In this material the electron spins fail to find an ordered state and thus are frustrated.  Their spins (called quantum spins) mimic water, which lacks any long-range order, and hence these odd materials are called quantum spin liquids.  This...

    Read More
  • Excited state of the solid-state emitter is shifted by random amount Δ from the desired position. The optical 180° control pulses are applied periodically, with a delay τ. In the rotating frame, each pulse swaps the ground and the excited state, reversing the detuning Δ → −Δ.

    Much like being slightly off the frequency of a radio station destroys radio reception, the quality of light-emitting technologies has, until now, been severely limited by random fluctuations in the frequency of the emitted photons.  Scientists demonstrated how this photon detuning can be suppressed using a series of short, controlled pulses applied to the emitter.  The elegant solution is robust and applicable for many quantum systems, removing a major roadblock on the way to implementing large-scale quantum networks.  The heart of these quantum-enhanced technologies is the solid-state...

    Read More
  • Cover featuring an image from Petit et al. The figure shows the 3D Fermi surface for a paramagnetic compound of gadolinium and magnesium.

    Theoretical modeling has led to a key development in our understanding of the deeply complex magnetic properties in a series of rare-earth intermetallic materials.  Rare-earth elements are unique in that their cores hold strongly localized electrons that underpin their novel magnetic properties.  When combined with transition metals, rare earths become technologically-useful intermetallic materials.  Here gadolinium—an element from the middle of the rare earth series—and either magnesium, zinc, or cadmium was combined to create the materials.  Researchers developed a theory explaining how...

    Read More
  • Shown is the temperature dependence of the band dispersion at the hole pocket divided by the Fermi function.  Researchers found that upon increase of the temperature the electron pockets remain intact, while the hole pockets vanished above 165 K. The pink arrow points to a band located above the hole band.

    For the first time, a temperature-driven contour change in an electron behavioral map—known as the Fermi surface—has been reported.  The key properties of conducting materials are determined by the behavior of the electrons that reside on so called “Fermi surface.”  Changes in the shape of this surface, known as Lifshitz transitions, previously were seen only when substantial pressure was applied or the chemical composition of the material was modified.  Employing a technique that uses light energy (photons) to study electron properties within a sample, known as angle-resolved...

    Read More
  • Extensive calculations revealed that the calcium-iridium-oxygen compound CaIrO3 is a Slater-type insulator, putting to rest the debate of whether the insulating nature of the metal oxide is Mott-type or Slater-type.  While both types are insulators, the insulating properties in Mott types arise from electron repulsion while in Slater types magnetic ordering plays a prominent role.  Through a series of calculations, the team described the types of interactions between the various atoms in the oxide.  Their calculations took temperature into consideration, because it is known...

    Read More
  • A compound made out of ytterbium (Yb), platinum (Pt), and bismuth (Bi) offers researchers the opportunity to watch the birth of magnetic behavior by applying small changes in magnetic field or temperature.  Despite the electrons having effective masses of nearly 10,000 times their normal mass when YbPtBi becomes magnetic, researchers have been able to monitor its quantum oscillations, key for determining important electronic properties.  From the results they deduced that as it moves further and further from magnetism its electrons lose weight fast.  These findings provide key...

    Read More
  • Two types of magnetic configurations—antiferromagnetism (AFM) and ferromagnetism (FM)—have been found to compete with each other, thwarting the rise of superconductivity in iron pnictides, a class of high-temperature superconductors.  In an AFM fluctuation electron spins temporary align in an alternating checkboard pattern while electron spins align temporary in the same direction in a FM fluctuation.  While FM fluctuations have been suggested in the iron pnictide superconductors by theoretical calculations, the possible existence of FM fluctuations has not yet been examined from a...

    Read More
  • Oxygen is one of the most ubiquitous elements in chemistry and materials science, yet one of the most elusive elements for spectroscopic investigation by solid-state Nuclear Magnetic Resonance (SSNMR). Used to determine the structure of materials and chemicals on the atomic scale, SSNMR requires nuclei that have magnetic moments. Yet, less than four of every 10,000 oxygen nuclei are 17O, the only NMR-active isotope of oxygen. Detecting the elusive oxygen isotope now has become a reality thanks to unprecedented advancement in SSNMR, referred to as Dynamic Nuclear Polarization (...

    Read More

Pages