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Creators/Authors contains: "Engel, L W"

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  1. ; ; ; ; ; (, Physical Review B)
    This paper reports the discovery that resistively-coupled coplanar waveguides in van der Waals heterostructures are dominated by Hall conductivity rather than longitudinal conductivity, unlike traditional capacitively-coupled systems. We observed clear integer quantum Hall effect plateaus that were frequency-independent from below 1 GHz to over 7 GHz, with sensitivity strongly dependent on device geometry. We developed a T-network circuit model that successfully explains the nearly threefold enhancement in measurement sensitivity observed in samples with long contact regions compared to theoretical predictions. This work establishes important design principles for microwave measurements of two-dimensional electron systems in van der Waals materials and opens pathways for contactless characterization of materials where Ohmic contacts are challenging to achieve. 
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  2. ; ; ; ; ; ; ; (, Physical Review Letters)
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  3. ; ; ; ; ; ; ; (, Physical Review Letters)
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  4. ; ; ; ; ; ; ; ; ; ; et al (, Physical Review Letters)
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  6. ; ; ; ; ; (, Physical Review Letters)
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  8. ; ; ; ; ; ; ; (, Science Advances)
    We studied a bilayer system hosting two-dimensional electron systems (2DESs) in close proximity but isolated from one another by a thin barrier. One 2DES has low electron density and forms a Wigner solid (WS) at high magnetic fields. The other has much higher density and, in the same field, exhibits fractional quantum Hall states (FQHSs). The WS spectrum has resonances which are understood as pinning modes, oscillations of the WS within the residual disorder. We found the pinning mode frequencies of the WS are strongly affected by the FQHSs in the nearby layer. Analysis of the spectra indicates that the majority layer screens like a dielectric medium even when its Landau filling is ~ 1 / 2 , at which the layer is essentially a composite fermion (CF) metal. Although the majority layer is only ~ one WS lattice constant away, a WS site only induces an image charge of ~0.1e in the CF metal. 
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  9. ; ; ; ; ; ; (, Physical Review B)
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