Nanowerk September 9, 2021 Researchers in Japan used the surface activated bonding (SAB) method to successfully bond GaN and diamond and demonstrated that the bonding is stable even when heated to 1,000°C. A 5.3 nm-thick intermediate layer composed of amorphous carbon and diamond is formed at the as-bonded heterointerface. As the team increased annealing temperatures, the layer thickness decreased suggesting the intermediate layer can be completely removed by optimizing the annealing process. As no peeling was observed at the heterointerface after annealing at 1000°C these results indicate that the GaN/diamond heterointerface can withstand harsh fabrications processes. The material shows promise […]
Graphene valleytronics: Paving the way to small-sized room-temperature quantum computers
Phys.org September 8, 2021 Electrons in two-dimensional hexagonal materials have an extra degree of freedom that can be used to encode and process quantum information. An international team of researchers (India, Germany) demonstrated that both valley-selective excitation and valley-selective high-harmonic generation can be achieved in pristine graphene by using a combination of two counter-rotating circularly polarized fields, the fundamental and its second harmonic. Controlling the relative phase between the two colors allowed them to select the valleys where the electron–hole pairs and higher-order harmonics are generated. They described an all-optical method for measuring valley polarization in graphene with a weak […]
Lead-free rare-earth-based double perovskite nanocrystals with near-infrared emission
Nanowerk September 9, 2021 Researchers in China synthesized all-inorganic rare-earth-based Cs2NaEr1−xBxCl6 double perovskite nanocrystals. The Cs2NaErCl6 NCs showed good air stability and emitted a sharp NIR photoluminescence at telecommunication wavelength of 1543 nm and its average lifetime is 35.7 µs. For Cs2NaEr0.5Sb0.5Cl6 nanocrystals NIR photoluminescence could be enhanced 23-fold with the lifetime being 119.1 µs. Femtosecond transient absorption measurements proved that a long-lifetime trap state promotes NIR emitting in the mixed Sb/Er double perovskite nanocrystals…read more. TECHNICAL ARTICLE
New theory for detecting light in the darkness of vacuum
Phys.org September 8, 2021 An accelerating photodetector is predicted to see photons in the electromagnetic vacuum. However, the extreme accelerations required have prevented the direct experimental verification of this quantum vacuum effect. Researchers at Dartmouth College considered many accelerating photodetectors that are contained within an electromagnetic cavity. They showed that the resulting photon production from the cavity vacuum can be collectively enhanced such as to be measurable. When the detector number exceeds a certain critical value, the vacuum photon production undergoes a phase transition from a normal phase to an enhanced super radiant-like, inverted lasing phase. Such a model may […]
Physicists engineer new property out of ‘white’ graphene
Nanowerk September 7, 2021 An international team of researchers (USA – MIT, Japan) has demonstrated that when two single sheets of boron nitride are stacked parallel to each other, at room temperature, the material becomes ferroelectric, in which positive and negative charges in the material spontaneously head to different sides, or poles. Upon the application of an external electric field, those charges switch sides, reversing the polarization. Twisting the boron nitride sheets by a small angle changes the dynamics of switching because of the formation of moiré ferroelectricity with staggered polarization. The coupling between vertical polarization and horizontal motion is […]
Researchers reveal a novel metal where electrons flow with fluid-like dynamics
Phys.org September 6, 2021 An international team of researchers (USA -Boston College, Florida State University, UT Dallas, Switzerland) found that a strong interaction between electrons and phonons alters the transport of electrons from the diffusive, or particle-like, to hydrodynamic, or fluid-like, regime in a synthesis of Niobium and Germanium (NbGe2). Electrical resistivity measurements showed a higher-than-expected mass for electrons, and X-ray diffraction revealed the crystal structure of the material. The mass of electrons in all trajectories was three times larger than the expected value. The strong electron-phonon interaction was responsible for the heavy electron behavior. In future work the team […]
Researchers use gold film to enhance quantum sensing with qubits in a 2D material
Phys.org September 3, 2021 The photoluminescence and the contrast of the optically detected magnetic resonance (ODMR) of hexagonal boron nitride (hBN) spin defects are relatively low so far, which limits their sensitivity. An international team of researchers (USA – Purdue University, Australia) used a gold film to increase the brightness of spin qubits by up to 17-fold. The gold film supports the surface plasmon that can speed up photon emission and hence more signals. They improved the contrast of their magnetic resonance signal by a factor of 10 by optimizing the design of a microwave waveguide substantially improving the sensitivity […]
Researchers use organic semiconductor nanotubes to create new electrochemical actuator
Phys.org September 3, 2021 To improve the movement and response time for electrochemical actuator devices that operate in liquid a team of researchers at the University of Houston has developed electrochemical actuator that uses specialized organic semiconductor nanotubes (OSNTs). The device demonstrated excellent performance, low power consumption/strain, a large deformation, fast response, and excellent actuation stability. The enormous effective surface area of the nanotubular structure which facilitates the ion transport and accumulation results in high electroactivity and durability. The work provides new opportunities for next-generation actuators that can be utilized in artificial muscles and biomedical devices…read more. TECHNICAL ARTICLE
Stretching the capacity of flexible energy storage (w/video)
Nanowerk September 8, 2021 In spite of the excellent electrical and electrochemical properties, two-dimensional transition metal carbide (MXene) is often limited by the high stiffness for the direct implementation in next-generation stretchable and wearable energy storage devices. After screening for the thickness, researchers in China identified the crumpled MXene film of ∼3 μm in thickness as the optimal choice to mitigate the crack formations under large and repetitive mechanical strains. The as-prepared symmetric supercapacitor demonstrated a high specific capacitance of ∼470 mF cm–2, ultrahigh stretchability up to 800% area strain, and >90% retention of the initial capacitance after 1000 stretch–relaxation […]
Tapping into magnets to clamp down on noise in quantum information
Phys.org September 3, 2021 Building on their earlier efforts to create a superconducting circuit integrated with magnetic elements, a team of researchers in the US (Argonne National Laboratory, University of Illinois) is investigating whether magnons could partner with microwave photons to ensure that microwaves can only travel in one direction, thereby essentially eliminating noise. They will be testing known and new material systems to find candidates that can handle an ultracold environment and operate in a real quantum device. According to the researchers if they are successful, it is possible to have magnetic structures directly integrated with quantum circuitry. The […]