Publications by authors named "D L Maude"
The mixed-valence compound YbB displays paradoxical quantum oscillations in electrical resistivity and magnetic torque in a regime with a well-developed insulating charge gap and in the absence of an electronic Fermi surface. However, signatures of such unusual fermionic quasiparticles in other bulk thermodynamic observables have been missing. Here we report the observation of a series of sharp double-peak features in the specific heat as a function of the magnetic field.
View Article and Find Full Text PDFIn metal halide perovskites, the complex dielectric screening together with low energy of phonon modes leads to non-negligible Fröhlich coupling. While this feature of perovskites has already been used to explain some of the puzzling aspects of carrier transport in these materials, the possible impact of polaronic effects on the optical response, especially excitonic properties, is much less explored. Here, with the use of magneto-optical spectroscopy, we revealed the non-hydrogenic character of the excitons in metal halide perovskites, resulting from the pronounced Fröhlich coupling.
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- The optical behavior of 2D perovskites relies heavily on excitons, which can be manipulated by altering the thickness of the perovskite layers.
- Researchers studied the exciton fine structure in a specific 2D perovskite by varying the number of inorganic layers from 1 to 4.
- Their findings reveal splitting of excitonic states across different confinement levels and show how the optical properties transition from 2D to 3D as the layer thickness increases.
Article Synopsis
- The optical response of 2D layered perovskites features closely spaced spectral signatures, interpreted as phonon replicas, with an energy separation ranging from 12 to 40 meV, depending on the material.
- These materials also show a strong scattering response in resonant Raman spectroscopy above roughly 200 cm (or 25 meV), which is linked to the presence of polarons, exhibiting a distinctive spectral pattern deviating from the Rayleigh line.
- A significant Huang-Rhys factor (S > 6) suggests strong coupling between charge carriers and the lattice, with polaron binding energies between 20-35 meV, influencing the optical properties critical for future opto-electronic applications.
Quantum oscillation phenomenon is an essential tool to understand the electronic structure of quantum matter. Here we report a systematic study of quantum oscillations in the electronic specific heat C in natural graphite. We show that the crossing of a single spin Landau level and the Fermi energy give rise to a double-peak structure, in striking contrast to the single peak expected from Lifshitz-Kosevich theory.
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