We demonstrate a high-temperature nanoscale super-Schottky diode based on a superconducting tunnel junction of pulsed-laser-deposited YBCO on GaN thin films. A buffer-free direct growth of nanoscale YBCO thin films on heavily doped GaN was performed to realize a direct high-Tc superconductor-semiconductor junction. The junction shows strongly non-linear I-V characteristics, which have practical applications as a low-voltage super-Schottky diode for microwave mixing and detection. The V-shaped differential conductance spectra observed across the junction are characteristic of the c-axis tunneling into a cuprate superconductor with a certain disorder level. This implementation of the super-Schottky diode, supported by the buffer-free direct growth of nanoscale high-Tc thin films on semiconductors, paves the way for practical large-scale fabrication and integration of high-Tc-superconductor devices in future technologies.

We dynamically modulate strong light-matter coupling in a GaAs/AlGaAs microcavity using intense ultrashort laser pulses tuned below the interband exciton energy, which induce a transient Stark shift of the cavity polaritons. For 225-fs pulses, shorter than the cavity Rabi cycle period of 1000 fs, this shift decouples excitons and cavity photons for the duration of the pulse, interrupting the periodic energy exchange between photonic and electronic states. For 1500-fs pulses, longer than the Rabi cycle period, however, the Stark shift does not affect the strong coupling. The two regimes are marked by distinctly different line shapes in ultrafast reflectivity measurements-regardless of the Stark field intensity. The crossover marks the transition from adiabatic to diabatic switching of strong lightmatter coupling.The achievement of strong coupling between light fields and matter excitations has marked a cornerstone of modern physics, both from a fundamental science viewpoint and for the implementation of new classical and quantum technologies. On the one hand, the ability to engineer repeated cycles of energy exchange between single atoms or atomic Bose-Einstein condensates (BEC) and photons confined in cavities, led to the development of a new research branch of cavity quantum electrodynamics, which allowed for implementation and testing of textbook Gedanken experiments [1,2]. This progress is closely related to the emerging field of quantum information science, constituting the first test-bed for the implementation of secure quantum communication

We demonstrate ultrafast control of a strongly coupled light–matter system via a giant ac Stark effect in a specially designed strongly coupled microcavity using ultrafast pump–probe spectroscopy. We observe polariton energy shifts larger than the Rabi energy, enabling the implementation of strong noninvasive potentials for robust and ultrafast polaritonic switches. A nonperturbative treatment has been utilized to correctly describe the underlying physics of the giant Stark shifts in our strongly coupled light–matter system and corresponds well to the experimental results. Our findings shed new light on nonperturbative interactions and pave the way for all-optical quantum technologies.

We demonstrate efficient linear-optical access to surface-state spin dynamics in Bi2Se3 by probing transitions between two surface-state Dirac cones, providing a practical technique for spin-current dynamics studies in topological-insulator devices. Using broadband transient-reflectivity pump-probe measurements, we distinguish bulk and surface state-responses, by controlling photon energy and circular polarization at oblique incidence. For pump-photon energies corresponding to bulk-state transitions, the probe polarized co-circularly with the pump shows stronger reflectivity change, compared to the anti-circularly polarized probe. However, pump photon energies corresponding to surface-state transitions result in an opposite effect, with the anti-circularly polarized probe exhibiting stronger reflectivity change. This surprising behavior stems from the surface-state in-plane spin orientation near the Dirac point, and the surface-state spin population remains at the injected energy for several ps. These results enable an efficient approach for studying spin current dynamics in topological-insulator based technologies.

We observe Andreev reflection in a YBCO-GaN junction through differential conductance spectroscopy. A strong characteristic zero-bias peak was observed and persisted up to the critical temperature of the superconductor with a smaller superconducting order parameter Δ ∼ 1 meV. The presence of Andreev reflection with the small Δ in comparison to its value for high-T c superconductors forms an important milestone toward demonstration of superconducting proximity in high-T c /semiconductor junctions. Experimental results were then compared to the theoretical model with good agreement. Efficient injection of Cooper pairs into direct bandgap semiconducting structures, together with high transition temperature of YBCO, can pave the way to novel optoelectronics and quantum optical studies of high-T c materials.