Phys.org April 16, 2024 Harnessing the asymmetric electronic population in the conduction band induced by an intense single-color circularly polarized laser pulse an international team of researchers (Japan, India, Germany) developed a universal method to generate ultrafast photocurrent in both inversion-symmetric and inversion-broken Weyl semimetals with degenerate Weyl nodes at the Fermi level. They found that the induced photocurrent could be tailored by manipulating helicity and ellipticity of the employed laser. Their approach generated photocurrent in realistic situations when the Weyl nodes were positioned at different energies and had finite tilt along a certain direction. According to the researchers their […]
Tag Archives: Optoelectronics
Physicists shine light on solid way to extend excitons’ life
Phys.org June 20, 2022 A team of researchers in the US (UT Austin, Auburn University) performed an extensive study of transient optical absorption of both W- and Mo-based single-crystalline monolayer TMDs grown by a recently developed laser-assisted evaporation method. All spectral features of the monolayers as grown on fused silica substrates exhibited appreciable redshifts relating to the existence of strain due to growth conditions. These systems exhibited a dramatic slowing down of exciton dynamics with an increase in carrier densities, which strongly contrasted with the monolayers in their freestanding form as well as in comparison with more traditionally grown TMDs. […]
Molecular interfaces for innovative sensors and data storage devices
Nanowerk October 20, 2021 To better understand electronic and magnetic properties and understanding the mechanisms that govern the interactions at the interface an international team of researchers (Germany, Austria, Switzerland, Italy) coupled nickel-porphyrin with copper. Using theoretical and experimental spectro-microscopy approach they showed that the charge transfer occurring at the interface between nickel tetraphenyl porphyrins and copper changes both spin and oxidation states of the Ni ion. The chemically active Ni(I), even in a buried multilayer system, can be functionalized with nitrogen dioxide, allowing a selective tuning of the electronic properties of the Ni center that is switched to a […]
Quantum material to boost terahertz frequencies
Science Daily October 20, 2021 An international team of researchers (Germany, Spain, Russia) investigated the ultrafast carrier dynamics in topological insulators (TIs) of the bismuth and antimony chalcogenide family, where they isolated the response of Dirac fermions at the surface from the response of bulk carriers by combining photoexcitation with below-bandgap terahertz (THz) photons and TI samples with varying Fermi level, including one sample with the Fermi level located within the bandgap. They identified distinctly faster relaxation of charge carriers in the topologically protected Dirac surface states, compared to bulk carriers and they observed THz harmonic generation without any saturation […]
One material with two functions could lead to faster memory
Science Daily August 23, 2021 Previous versions of light-emitting memories required the integration of two separate devices with differing materials, complicating fabrication. Using just one perovskite layer between contacts an international team of researchers (Taiwan, Japan) fabricated a device that works both as a RRAM and a light-emitting electrochemical cell. By taking advantage of the fast, electrically switchable ionic motion that enables this dual functionality in a single layer of perovskite they connected two devices together and developed an all-inorganic perovskite light-emitting memory. They used perovskite quantum dots of two different sizes for the two devices in the light-emitting memory […]
A performance leap for graphene modulators in next generation datacom and telecom
Nanowerk February 16, 2021 Electro-absorption (EA) waveguide-coupled modulators are essential building blocks for on-chip optical communications. Compared to state-of-the-art silicon devices, graphene-based EA modulators promise smaller footprints, larger temperature stability, cost-effective integration, and high speeds. However, combining high speed and large modulation efficiencies in a single graphene-based device has remained elusive so far. An international team of researchers (Spain, Italy, Belgium) overcame this fundamental trade-off by demonstrating the 2D-3D dielectric integration in a high-quality encapsulated graphene device. They integrated hafnium oxide and two-dimensional hexagonal boron nitride within the insulating section of a double-layer graphene EA modulator. This combination of materials […]
A Quantum Tango between Magnons and Phonons
American Physical Society October 26, 2020 A magnon polaron, hybridized state of a phonon and a magnon, can be formed at the intersection of the magnon and phonon dispersions, where their frequencies coincide. However, the weak interaction of magnons and phonons and their short lifetimes jeopardize the strong coupling required for the formation of a hybridized state. An international team of researchers (Germany, Russia, Ukraine, UK) overcame these limitations by spatial matching of magnons and phonons in a metallic ferromagnet with a nanoscale periodic surface pattern. The spatial overlap results in a high coupling strength which, in combination with their […]
Graphene sets a new record on squeezing light to one atom
Science Daily April 20, 2018 An international team of researchers (Spain, France, Portugal, USA – MIT) has shown that a graphene-insulator-metal heterostructure can overcome energy loss and demonstrate plasmon confinement down to the ultimate limit of the length scale of one atom. This is achieved through far-field excitation of plasmon modes squeezed into an atomically thin hexagonal boron nitride dielectric spacer between graphene and metal rods. A theoretical model that takes into account the nonlocal optical response of both graphene and metal is used to describe the results. These ultraconfined plasmonic modes, addressed with far-field light excitation, enable a route […]