Nanowerk August 11, 2021 For most solids, the thermally emitted power increases monotonically with temperature in a one-to-one relationship that enables applications such as infrared imaging and noncontact thermometry. A team of researchers in the US (University of Wisconsin–Madison, Harvard University, Purdue University, Brookhaven National Laboratory) has demonstrated that ultrathin thermal emitters that violate this one-to-one relationship via the use of samarium nickel oxide (SmNiO3), a strongly correlated quantum material that undergoes a fully reversible, temperature-driven solid-state phase transition. Due to the smooth and hysteresis-free nature of this unique insulator-to-metal phase transition enabled them to engineer the temperature dependence of […]
Tag Archives: Materials science
Effective EMI shielding behavior of thin graphene/PMMA nanolaminates
Phys.org August 4, 2021 The use of graphene in a form of discontinuous flakes in polymer composites limits the full exploitation of the unique properties of graphene, thus requiring high filler loadings for achieving satisfactory electrical and mechanical properties. An international team of researchers (Greece, Italy) produced centimetre-scale CVD graphene/polymer nanolaminates by using an iterative ‘lift-off/float-on’ process. These have outperformed, for the same graphene content, state-of-the-art flake-based graphene polymer composites in terms of mechanical reinforcement and electrical properties. The thin laminate materials have shown a high electromagnetic interference (EMI) shielding effectiveness, reaching 60 dB for a small thickness of 33 μm, […]
Dancing with the light: A new way to make crystals bend by shining light
Nanowerk July 30, 2021 Only very thin crystals (up to 20 microns) can show appreciable mechanical response. Researchers in Japan accidentally discovered that the photothermal effect causes a crystal to bend fast. To create a new, faster bending crystal and clarify the underlying mechanism, they exposed a thin salicylideneaniline derivative crystal to UV light and obtained substantial bending within approximately 1 second. However, the bend angle dropped rapidly with increasing crystal thickness, revealing that the bending was caused by photoisomerization. When they illuminated a thick (>40 microns) crystal with UV light, they observed an extremely rapid bending within several milliseconds, […]
Achilles heel of graphene exposed
Nanowerk July 19, 2021 The quantum Hall effect is the seminal example of topological protection as charge carriers are transmitted through one-dimensional edge channels where backscattering is prohibited. In conventional Hall bar geometries, topological protection of graphene edge channels is found less robust than in high mobility semi-conductors. An international team of researchers (Belgium, Germany, Japan) exploring graphene quantum Hall regime at the local scale revealed that the detrimental influence of antidots along the graphene edges, mediating backscattering towards upstream edge channels triggering topological breakdown. The finding is a major step forward in the understanding of the quantum Hall effect […]
The demonstration of ultrafast switching to an insulating-like metastable state
Phys.org July 13, 2021 Superconductors host collective modes that can be manipulated with light. An international team of researchers (Japan, France) has shown that a strong terahertz light field can induce oscillations of the superconducting order parameter in NbN with twice the frequency of the terahertz field. The result can be captured as a collective precession of Anderson’s pseudospins in ac driving fields. A resonance between the field and the Higgs amplitude mode of the superconductor then results in large terahertz third-harmonic generation. Their method paves a way toward nonlinear quantum optics in superconductors with driving the pseudospins collectively and […]
New evidence of an anomalous phase of matter brings energy-efficient technologies closer
Phys.org July 14, 2021 An international team of researchers (UK, Japan, Slovenia, India, USA – Columbia University, Switzerland) used ultrafast pump-probe microscopy to investigate the possible excitonic insulator Ta2NiSe5. Below 328 K, they observed the anomalous micrometer-scale propagation of coherent modes at velocities of ~105 m/s, which they attributed to the hybridization between phonon modes and the phase mode of the condensate. They developed a theoretical framework to support this explanation and proposed that electronic interactions provide a substantial contribution to the ordered phase in Ta2NiSe5. These results allow us to understand how the condensate’s collective modes transport energy and […]
Researchers identify ultrastable single atom magnet
Phys.org July 7, 2021 An international team of researchers (South Korea, Germany) has shown that dysprosium (Dy) atoms on magnesium oxide (MgO) have a giant (magnet/ic anisotropy energy) MAE of 250 meV, currently the highest among all surface spins. Using a variety of scanning tunnelling microscopy (STM) techniques including single atom electron spin resonance (ESR), they confirmed that there was no spontaneous spin-switching in Dy over days at ≈ 1 K under low and even vanishing magnetic field. They utilized these robust Dy single atom magnets to engineer magnetic nanostructures, demonstrating unique control of magnetic fields with atomic scale tunability. The work […]
Stress-free path to stress-free metallic films paves the way for next-gen circuitry
Nanowerk July 4, 2021 To create thin films of tungsten with unprecedentedly low levels of film stress researchers in Japan have been working with scattering (HiPIMS), a sputtering technique. Using argon gas and a tungsten target, the team looked at how ions with different energies arrived at the substrate over time in unprecedented detail. Instead of using a bias pulse set off at the same time as the HiPIMS pulse, they used their knowledge of when different ions arrived and introduced a tiny delay, 60 microseconds, to precisely select for the arrival of high energy metal ions. They found that […]
Scientists design 3D-grown material that could speed up production of new technologies for smart buildings and robotics
Phys.org June 29, 2021 An international team of researchers (UC Berkeley, Lawrence Berkeley National Laboratory, UK) has developed a nanoparticle composite that grows into 3-D crystals. They discovered that a tiny trace of polyolefin molecules from the centrifuge tube lining had somehow entered the mix. Subsequent experiments revealed that as the toluene solvent quickly evaporates at room temperature, the polyolefin additive helps the Au-PS nanoparticles form into 3D PGNP crystals, and to grow into crystal structure and the size and shape of the 3D PGNP crystals are driven by the kinetic energy of olyolefins as they precipitate in the solution. […]
Transforming a van-der-Waals ferromagnet for future spintronics
Nanowerk June 28, 2021 An international team of researchers (Australia, China) demonstrated that ultra-high electron doping concentration (above 1021 cm-3) can be induced in the layered van der Waals (vdW) metallic material Fe5GeTe2 by proton intercalation and can further cause a transition of the magnetic ground state from ferromagnetism to antiferromagnetism. Compared to itinerant ferromagnets, antiferromagnets (AFMs) have unique advantages as building blocks of such future spintronic devices. Their robustness to stray magnetic fields makes them suitable for memory devices. All the samples showed that the ferromagnetic state can be gradually suppressed by increasing proton intercalation, and finally several samples […]