Enhancing electron correlation in a weakly interacting topological system has great potential to promote correlated topological states of matter with extraordinary quantum properties. Here, the enhancement of electron correlation in a prototypical topological metal, namely iridium dioxide (IrO2), via doping with 3d transition metal vanadium is demonstrated. Single‐crystalline vanadium‐doped IrO2 nanowires are synthesized through chemical vapor deposition where the nanowire yield and morphology are improved by creating rough surfaces on substrates. Vanadium doping leads to a dramatic decrease in Raman intensity without notable peak broadening, signifying the enhancement of electron correlation. The enhanced electron correlation is further evidenced by transport studies where the electrical resistivity is greatly increased and follows an unusual T$\sqrt T $ dependence on the temperature (T). The lattice thermal conductivity is suppressed by an order of magnitude via doping even at room temperature where phonon‐impurity scattering becomes less important. Density functional theory calculations suggest that the remarkable reduction of thermal conductivity arises from the complex phonon dispersion and reduced energy gap between phonon branches, which greatly enhances phase space for phonon–phonon Umklapp scattering. This work demonstrates a unique system combining 3d and 5d transition metals in isostructural materials to enrich the system with various types of interactions.
Various electrophysiological and imaging techniques have been studied for the diagnosis and treatment of epilepsy. In particular, electrocorticography (ECoG) provides valuable information that can guide clinical treatment of patients with epilepsy. Currently, it is necessary to define the clinical benefits of ECoG in free-moving animals for the treatment of epilepsy. Here, we present the results of simultaneous recordings of multiple cortical sites and responsive neurostimulations for epilepsy treatment carried out in free-moving rats. In this study, we developed a high-density, flexible electrode array comprising graphene/Au/graphene that stably wraps onto the cortex surface of a living rat brain, exhibiting a superior signal-to-noise ratio. The hybrid graphene multichannel electrode successfully detected brain signals with high-throughput spatiotemporal resolution and substantially suppressed pilocarpine-induced epileptic discharges and behavior. Simultaneous recording and neurostimulation in awake animals can lead to a fundamental change in the treatment of medically intractable epilepsy.
We have employed one of the well-known many-body techniques, density functional theory plus dynamical mean-field theory (DFT + DMFT), to investigate the electronic structure of ferromagnetic monolayer CrI3 as a function of temperature and hole-doping concentration.The computed magnetic susceptibility follows the Curie's law, indicating that the ferromagnetism of monolayer CrI3 originates from localized magnetic moments of Cr atoms rather than Stoner-type itinerant ones. The DFT + DMFT calculations show a different coherent temperature for each spin component, demonstrating apparent strong spin-dependent electronic correlation effects in monolayer CrI3. Furthermore, we have explored the doping-dependent electronic structure of monolayer CrI3 and found that its electronic and magnetic properties is easily tunable by the hole-doping.
Various electrophysiological and imaging techniques have been studied for the diagnosis and treatment of epilepsy. In particular, electrocorticography (ECoG) provides valuable information that can guide clinical treatment in patients with epilepsy. To date, it is necessary to define the clinical benefits of ECoG in free-moving animals for the treatment of epilepsy. Here, we present the results of simultaneous recordings of multiple cortical sites and responsive neurostimulations for epilepsy treatment carried out in free-moving rats. In this study, we developed a high-density, flexible electrode array comprising graphene/Au/graphene which stably wraps onto the cortex surface of living rat’s brain, exhibiting superior signal-to-noise ratio. The hybrid graphene multichannel electrode successfully detected brain signals with high-throughput spatiotemporal resolution and substantially suppressed pilocarpine-induced epileptic discharges and behavior. The simultaneous recording and neurostimulation in awake animals can lead to a fundamental change in the approaches used for the treatment of medically intractable epilepsy.
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