Unconventional Fermi surface in an insulating state Tan, B. S.; Hsu, Y.-T.; Zeng, B. ...
Science (American Association for the Advancement of Science),
07/2015, Letnik:
349, Številka:
6245
Journal Article
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Insulators occur in more than one guise; a recent finding was a class of topological insulators, which host a conducting surface juxtaposed with an insulating bulk. Here, we report the observation of ...an unusual insulating state with an electrically insulating bulk that simultaneously yields bulk quantum oscillations with characteristics of an unconventional Fermi liquid. We present quantum oscillation measurements of magnetic torque in high-purity single crystals of the Kondo insulator SmB6, which reveal quantum oscillation frequencies characteristic of a large three-dimensional conduction electron Fermi surface similar to the metallic rare earth hexaborides such as PrB6 and LaB6. The quantum oscillation amplitude strongly increases at low temperatures, appearing strikingly at variance with conventional metallic behavior.
With increasing use of lithium-ion power packs, reports of occasional incidents of severely debilitating and sometimes fatal tragedies appear in the news. This review analyzes possible scenarios that ...trigger such hazards before proceeding to discuss safety mechanisms such as pressure release valves, one-shot fuses, reversible and irreversible positive temperature coefficient elements, shutdown separators, chemical shuttles, non-flammable electrolytes and coatings.
Magnetic skyrmions are topologically nontrivial particles with a potential application as information elements in future spintronic device architectures. While they are commonly portrayed as two ...dimensional objects, in reality magnetic skyrmions are thought to exist as elongated, tube-like objects extending through the thickness of the host material. The study of this skyrmion tube state (SkT) is vital for furthering the understanding of skyrmion formation and dynamics for future applications. However, direct experimental imaging of skyrmion tubes has yet to be reported. Here, we demonstrate the real-space observation of skyrmion tubes in a lamella of FeGe using resonant magnetic x-ray imaging and comparative micromagnetic simulations, confirming their extended structure. The formation of these structures at the edge of the sample highlights the importance of confinement and edge effects in the stabilisation of the SkT state, opening the door to further investigation into this unexplored dimension of the skyrmion spin texture.
Signatures of the Kondo effect in VSe2 Barua, Sourabh; Hatnean, M. Ciomaga; Lees, M. R. ...
Scientific reports,
09/2017, Letnik:
7, Številka:
1
Journal Article
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VSe2 is a transition metal dichaclogenide which has a charge- density wave transition that has been well studied. We report on a low-temperature upturn in the resistivity and, at temperatures below ...this resistivity minimum, an unusual magnetoresistance which is negative at low fields and positive at higher fields, in single crystals of VSe2. The negative magnetoresistance has a parabolic dependence on the magnetic field and shows little angular dependence. The magnetoresistance at temperatures above the resistivity minimum is always positive. We interpret these results as signatures of the Kondo effect in VSe2. An upturn in the susceptibility indicates the presence of interlayer V ions which can provide the localized magnetic moments required for scattering the conduction electrons in the Kondo effect. The low-temperature behaviour of the heat capacity, including a high value of γ, along with a deviation from a Curie-Weiss law observed in the low-temperature magnetic susceptibility, are consistent with the presence of magnetic interactions between the paramagnetic interlayer V ions and a Kondo screening of these V moments.
We report detailed investigations of the properties of a superconductor obtained by substituting In at the Sn site in the topological crystalline insulator (TCI), SnTe. Transport, magnetization, and ...heat capacity measurements have been performed on crystals of Sn sub(0.6)In sub(0.4) Te, which is shown to be a bulk superconductor with (ProQuest: Formulae and/or non-USASCII text omitted) at ~4.70(5) K and (ProQuest: Formulae and/or non-USASCII text omitted) at ~3.50(5) K. The upper and lower critical fields are estimated to be mu sub(0)Hc2 (0) = 1.42 (3) T and mu sub(0)Hc1 (0) = 0.90 (3) mT, respectively, while Kappa = 56.4(8) indicates this material is a strongly type-II superconductor.
•MgO nanoparticles are successfully synthesized using solution combustion method.•MgO nanoparticles with the crystallite size of ~27 nm are prepared by controlling the process parameters.•The ...photocatalytic studies indicated the 75% degradation efficiency after 120 min UV irradiation.
The present work is focused on the synthesize of MgO nanoparticles using combustion method. The magnesium nitrate is used as a precursor with urea as a fuel. The precursor material is dissolved in 50 ml DI water along with the fuel and the solution is heated at 80 °C for 2 h. Then, the solution is transferred to crucible and kept it in the temperature of 500 °C. The as-synthesized MgO nanopowders are analyzed using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Field emission scanning electron microscopy (FESEM), photoluminescence (PL) and photocatalytic studies. The XRD results of MgO nanoparticles indicated the cubic structure with the crystallite size of 27 nm. The FESEM studies indicated the formation of MgO crystallites in spherical shape. In addition, MgO nanoparticles are porous and agglomerated. PL spectrum of MgO materials exhibit emission peaks, which indicates the occurrence of band to band transition with the bandgap of 2.9 eV. The photocatalytic degradation of methylene blue dye is evaluated using the as-prepared MgO nanoparticles under UV light. The photocatalytic studies indicate the 75% degradation efficiency of the catalyst after 120 min irradiation. Hence, the MgO Nanoparticles (NPs) can be used for the treatment of effluents from the dye industries.
Magnetic skyrmions are topologically non-trivial, swirling magnetization textures that form lattices in helimagnetic materials. These magnetic nanoparticles show promise as high efficiency ...next-generation information carriers, with dynamics that are governed by their topology. Among the many unusual properties of skyrmions is the tendency of their direction of motion to deviate from that of a driving force; the angle by which they diverge is a materials constant, known as the skyrmion Hall angle. In magnetic multilayer systems, where skyrmions often appear individually, not arranging themselves in a lattice, this deflection angle can be easily measured by tracing the real space motion of individual skyrmions. Here we describe a reciprocal space technique which can be used to determine the skyrmion Hall angle in the skyrmion lattice state, leveraging the properties of the skyrmion lattice under a shear drive. We demonstrate this procedure to yield a quantitative measurement of the skyrmion Hall angle in the room-temperature skyrmion system FeGe, shearing the skyrmion lattice with the magnetic field gradient generated by a single turn Oersted wire.
Intrinsic topological insulators are realized by alloying Bi2Te3 with Bi2Se3. Angle‐resolved photoemission and bulk transport measurements reveal that the Fermi level is readily tuned into the bulk ...bandgap. First‐principles calculations of the native defect landscape highlight the key role of anti‐site defects for achieving this, and predict optimal growth conditions to realize maximally resistive topological insulators.
Visually impairments or blindness people need guidance in order to avoid collision risks with outdoor obstacles. Recently, technology has been proving its presence in all aspects of human life, and ...new devices provide assistance to humans on a daily basis. However, due to real-time dynamics or a lack of specialized knowledge, object detection confronts a reliability difficulty. To overcome the challenge, YOLO Glass a Video-based Smart object detection model has been proposed for visually impaired person to navigate effectively in indoor and outdoor environments. Initially the captured video is converted into key frames and pre-processed using Correlation Fusion-based disparity approach. The pre-processed images were augmented to prevent overfitting of the trained model. The proposed method uses an obstacle detection system based on a Squeeze and Attendant Block YOLO Network model (SAB-YOLO). A proposed system assists visually impaired users in detecting multiple objects and their locations relative to their line of sight, and alerts them by providing audio messages via headphones. The system assists blind and visually impaired people in managing their daily tasks and navigating their surroundings. The experimental results show that the proposed system improves accuracy by 98.99%, proving that it can accurately identify objects. The detection accuracy of the proposed method is 5.15%, 7.15% and 9.7% better that existing YOLO v6, YOLO v5 and YOLO v3, respectively.
The search for a Fermi surface in the absence of a conventional Fermi liquid has thus far yielded very few potential candidates. Among promising materials are spin-frustrated Mott insulators near the ...insulator–metal transition, where theory predicts a Fermi surface associated with neutral low-energy excitations. Here we reveal another route to experimentally realize a Fermi surface in the absence of a Fermi liquid by the experimental study of a Kondo insulator SmB6 positioned close to the insulator–metal transition. We present experimental signatures down to low temperatures (≪1 K) associated with a Fermi surface in the bulk, including a sizeable linear specific heat coefficient, and on the application of a finite magnetic field, bulk magnetic quantum oscillations, finite quantum oscillatory entropy, and substantial enhancement in thermal conductivity well below the charge gap energy scale. Thus, the weight of evidence indicates that despite an extreme instance of Fermi liquid breakdown in Kondo insulating SmB6, a Fermi surface arises from novel itinerant low-energy excitations that couple to magnetic fields, but not weak DC electric fields.
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