High broad‐band photoresponsivity of mechanically formed InSe–graphene van der Waals heterostructures is achieved by exploiting the broad‐band transparency of graphene, the direct bandgap of InSe, and the favorable band line up of InSe with graphene. The photoresponsivity exceeds that for other van der Waals heterostructures and the spectral response extends from the near‐infrared to the visible spectrum.

We present measurements of the dissipation and frequency shift in gold nanomechanical resonators at temperatures down to 10 mK. The resonators were fabricated as doubly clamped beams above a GaAs substrate and actuated magnetomotively. Measurements on beams with frequencies 7.95 and 3.87 MHz revealed that from 30 to 500 mK the dissipation increases with temperature as T 0.5 , with saturation occurring at higher temperatures. The relative frequency shift of the resonators increases logarithmically with temperature up to at least 400 mK. Similarities with the behavior of bulk amorphous solids suggest that the dissipation in our resonators is dominated by two-level systems.

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We present results from a study of the nonlinear inter-modal coupling between different flexural vibrational modes of a single high-stress, doubly-clamped silicon nitride nanomechanical beam. Using the magnetomotive technique and working at 100 mK we explored the nonlinear behaviour and modal couplings of the first, third and fifth modes of a 25.5 µm long beam. We find very good agreement between our results and a simple analytical model which assumes that the different modes of the resonator are coupled to each other by displacement induced tension in the beam. The small size of our resonator leads to relatively strong nonlinear couplings, for example we find a shift of about 7 Hz in the third mode for a 1 nm displacement in the first mode and frequency shifts ∼20 times larger than the linewidth (130 Hz) are readily observed.

We use dynamic scanning capacitance microscopy to image compressible and incompressible strips at the edge of a Hall bar in a twodimensional electron gas (2DEG) in the quantum Hall effect (QHE) regime. This method gives access to the complex local conductance, G ts , between a sharp metallic tip scanned across the sample surface and ground, comprising the complex sample conductance. Near integer filling factors we observe a bright stripe along the sample edge in the imaginary part of G ts . The simultaneously recorded real part exhibits a sharp peak at the boundary between the sample interior and the stripe observed in the imaginary part. The features are periodic in the inverse magnetic field and consistent with compressible and incompressible strips forming at the sample edge. For currents larger than the critical current of the QHE break-down the stripes vanish sharply and a homogeneous signal is recovered, similar to zero magnetic field. Our experiments directly illustrate the formation and a variety of properties of the conceptually important QHE edge states at the physical edge of a 2DEG.