We study the impact of electrical contact barriers in hybrid WSe$_2$-LiNbO$_3$-based acoustoelectric and acousto-photoelectric devices using a combination of scanning photocurrent and acousto-electric current spectroscopy. Static scanning photocurrent measurements provide a qualitative measure of the band-bending and spatial distribution of the Schottky barrier between semiconducting WSe$_2$ and gold electrodes whereas the surface acoustic wave-induced acousto-electric current reveals the height of the tunnelling barrier created by the van der Waals gap between the multilayered WSe$_2$ flake and the gold electrodes in addition to the Schottky barrier. The combination of both techniques shows a ten-fold increase in the photocurrent by the acoustic wave. Moreover, the observed spatial redistribution of the current is attributed to the interplay between the contact properties at the source and drain electrodes and the charge carrier dynamics induced by the surface acoustic wave. The ratio of acoustic wavelength to the electrical channel length is found to impact the SAW-induced charge carrier transport. For a channel length shorter than one acoustic wavelength, carriers undergo a seesaw-like motion which changes to charge conveyance for channel lengths comparable or exceeding the acoustic wavelength.

Technologies operating on the basis of quantum mechanical laws and resources such as phase coherence and entanglement are expected to revolutionize our future. Quantum technologies are often divided into four main pillars: computing, simulation, communication, and sensing & metrology. Moreover, a great deal of interest is currently also nucleating around energy-related quantum technologies. In this Perspective, we focus on advanced superconducting materials, van der Waals materials, and moiré quantum matter, summarizing recent exciting developments and highlighting a wealth of potential applications, ranging from high-energy experimental and theoretical physics to quantum materials science and energy storage.

Superconducting nanowire single photon detectors (SNSPDs) emerged in the last decade as a disruptive technology that features performance characteristics, such as high sensitivity, dynamic range and temporal accuracy, which are ideally suited for light detection and ranging (lidar) applications. Here, we report a time-of-flight (TOF) lidar system based on waveguide-integrated SNSPDs that excels in temporal accuracy, which translates into high range resolution. For single-shot measurements, we find resolution in the millimeter regime, resulting from the jitter of the time-of-flight signal of 21$\,$ps for low photon numbers. We further decrease this signal jitter to 11$\,$ps by driving the SNSPD into a multiphoton detection regime, utilizing laser pulses of higher intensity, thus improving range resolution. For multi-shot measurements we find sub-millimeter range-accuracy of 0.75$\,$mm and reveal additional surface information of scanned objects by visualizing the number of reflected photons and their temporal spread with the acquired range data in a combined representation. Our realization of a lidar receiver exploits favorable timing accuracy of waveguide-integrated SNSPDs and extends their operation to the multiphoton regime, which benefits a wide range of remote sensing applications.

We establish low-temperature resonant inelastic light scattering (RILS) spectroscopy as a tool to probe the formation of a series of moiré-bands in twisted WSe_{2} bilayers by accessing collective intermoiré-band excitations (IMBE). We observe resonances in RILS spectra at energies in agreement with inter-moiré band transitions obtained from an ab-initio based continuum model. Transitions between the first and second inter-moiré band for a twist angle of about 8° are reported and between first and second, third and higher bands for a twist of about 3°. The signatures from IMBE for the latter highlight a strong departure from parabolic bands with flat minibands exhibiting very high density of states in accord with theory. These observations allow to quantify the transition energies at the K-point where the states relevant for correlation physics are hosted.