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Title: Spectroscopy and transport in 2D materials

Abstract: Two dimensional materials are an extensive and powerful toolbox both for basic science and for advanced devices and applications, from low power electronics, autonomous sensors and IoT, to novel catalysis, energy storage and production.
Their enormous surface area, delicate tunability, and the consequences of quantum confinement produce exceptional properties including strength, carrier mobility, or thermal conductivity, and exotic transport phenomena such as the quantum Hall effect.
My group develops and applies cutting-edge numerical simulation tools to predict and explain the properties of novel materials. I will showcase several examples from recent work on the extreme quantum properties of 2D systems: First, alternative platforms for solid state quantum bits are in strong demand as existing versions work only at low temperature and are difficult to fabricate. We have investigated the spectroscopic properties of boron vacancies in monolayer boron nitride (Figure), in particular their deceptively simple photoluminescence spectrum. It can not be explained quantitatively by "simple symmetry breaking, and is the result of specific localized vibrational mode couplings. In passing this makes a very sensitive nano thermometer. Second, there is intense recent scrutiny of thermal transport in low dimensional materials, to optimize the performance of next generation semiconducting devices, and to gauge the potential of 2D materials for thermoelectricity and thermal management: it is much harder to confine phonons than electrons. In a joint experimental-theoretical endeavor we have examinedthe transport of heat through progressively thinner layers of the transition metal dichalcogenide MoSe2. 3D intuition about vibration waves reflecting off diffuse or specular interfaces breaks down as the waves are confined to a strictly 2D geometry; we find both experimentally and theoretically that the conductivity simply plateaus for thin layers, due to an exchange of weight between "acoustic-like" and "optic-like" modes. Previous measurements were scattered over several orders of magnitude due to experimental artefacts and the difficulties of  interpretation using effective models. We clear the path for a reliable quantification of thermal transport at the nanoscale.