The weak light-matter interaction in graphene can be enhanced with a number of strategies, among which sensitization with plasmonic nanostructures is particularly attractive. This has resulted in the development of graphene-plasmonic hybrid systems with strongly enhanced photodetection efficiencies in the visible and the IR, but none in the UV. Here, we describe a silver nanoparticle-graphene stacked optoelectronic device that shows strong enhancement of its photoresponse across the entire UV spectrum. The device fabrication strategy is scalable and modular. Self-assembly techniques are combined with physical shadow growth techniques to fabricate a regular large-area array of 50 nm silver nanoparticles onto which CVD graphene is transferred. The presence of the silver nanoparticles resulted in a plasmonically enhanced photoresponse as high as 3.2 A W-1 in the wavelength range from 330 nm to 450 nm. At lower wavelengths, close to the Van Hove singularity of the density of states in graphene, we measured an even higher responsivity of 14.5 A W-1 at 280 nm, which corresponds to a more than 10 000-fold enhancement over the photoresponse of native graphene.

Superfluid 3 He under nanoscale confinement has generated significant interest due to the rich spectrum of phases with complex order parameters that may be stabilized. Experiments have uncovered a variety of interesting phenomena, but a complete picture of superfluid 3 He under confinement has remained elusive. Here, we present phase diagrams of superfluid 3 He under varying degrees of uniaxial confinement, over a wide range of pressures, which elucidate the progressive stability of both the A-phase, as well as a growing region of stable pair density wave (PDW) state.

Investigations of two-dimensional electron systems (2DES) have been achieved with two model experimental systems, covering two distinct, non-overlapping regimes of the 2DES phase diagram, namely the quantum liquid phase in semiconducting heterostructures and the classical phases observed in electrons confined above the surface of liquid helium. Multielectron bubbles in liquid helium offer an exciting possibility to bridge this gap in the phase diagram, as well as to study the properties of electrons on curved flexible surfaces. However, this approach has been limited because all experimental studies have so far been transient in nature. Here we demonstrate that it is possible to trap and manipulate multielectron bubbles in a conventional Paul trap for several hundreds of milliseconds, enabling reliable measurements of their physical properties and thereby gaining valuable insight to various aspects of curved 2DES that were previously unexplored.

A wide variety of applications of microwave cavities, such as measurement and control of superconducting qubits, magnonic resonators, and phase noise filters, would be well served by having a highly tunable microwave resonance. Often this tunability is desired in situ at low temperatures, where one can take advantage of superconducting cavities. To date, such cryogenic tuning while maintaining a high quality factor has been limited to ∼ 500 MHz. Here we demonstrate a three-dimensional superconducting microwave cavity that shares one wall with a pressurized volume of helium. Upon pressurization of the helium chamber the microwave cavity is deformed, which results in in situ tuning of its resonant frequency by more than 5 GHz, greater than 60% of the original 8 GHz resonant frequency. The quality factor of the cavity remains approximately constant at ≈ 7 × 10 3 over the entire range of tuning. As a demonstration of its usefulness, we implement a tunable cryogenic phase noise filter, which reduces the phase noise of our source by approximately 10 dB above 400 kHz.Three dimensional (3D) microwave cavities have proven to be an indispensable part of many quantum systems. They have recently been used in conjunction with superconducting qubits 1 to make spectacular progress in the field of cavity QED, where they are integral components in the implementation of universal gate sets, 2 nondestructive measurement of single microwave photons, 3 and implementation of programmable interference between quantum memories. 4 When paired with ferromagnetic spheroids, 5 they readily exhibit strong coupling to spin resonances, 6,7 which has allowed for the field of cavity magnonics to flourish with applications such as bidirectional microwave-optical conversion 8 and resolving magnon number states. 9 When coupled to a mechanical element, such as a membrane 10 or superfluid helium, 11 they form an optomechanical system with the potential for exceedingly high cooperativities and quality factors, allowing for the rich toolbox of optomechanics to be employed.In all of these applications, cryogenic tunability of the microwave cavity -without sacrificing the quality factor (Q)would allow for the use of superconducting materials, desirable for the high quality factors they confer. For instance, one can imagine a superconducting qubit encapsulated inside a superconducting resonator. Normally, such a qubit is tuned by the application of a magnetic field, 12 but this is prohibited inside a superconducting cavity due to field exclusion from the Meissner effect. With a highly-tunable cavity, one could enjoy all the advantages of a superconducting cavity while still being able to control its detuning with respect to a qubit. Similarly for cavity magnonics, a highly-tunable cavity could allow control of the phonon-magnon hybridization without the need for a tunable magnetic field.In addition to their uses outlined above, microwave cavities are useful in both classical and quantum systems as phase noise filters. [13][14][15] Classically, phase noise...

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