No abstract

High‐temperature superconductors (HTSs) are important for potential applications and for understanding the origin of strong correlations. Bi2Sr2CaCu2O8+δ (BSCCO), a van der Waals material, offers a platform to probe the physics down to a unit‐cell. Guiding the flow of electrons by patterning 2DEGS and oxide heterostructures has brought new functionality and access to new science. Similarly, modifying superconductivity in HTS locally, on a small length scale, is of immense interest for superconducting electronics. A route to modify superconductivity locally by depositing metal on the surface is reported here by transport studies on few unit‐cell thick BSCCO. Deposition of chromium (Cr) on the surface over a selected area of BSCCO results in insulating behavior of the underlying region. Cr locally depletes oxygen in CuO2 planes and disrupts the superconductivity in the layers below. This technique of modifying superconductivity is suitable for making sub‐micrometer superconducting wires and more complex superconducting devices.

We investigate the performance of niobium nitride superconducting coplanar waveguide resonators toward realizing hybrid quantum devices with magnon-photon coupling. We find internal quality factors ∼ 20 000 at 20 mK base temperature, in zero magnetic field. We find that by reducing film thickness below 100 nm, an internal quality factor greater than 1000 can be maintained up to a parallel magnetic field of ∼ 1 T and a perpendicular magnetic field of ∼ 100 mT. We further demonstrate strong coupling of microwave photons in these resonators with magnons in chromium trichloride, a van der Waals antiferromagnet, which shows that these cavities serve as a good platform for studying magnon-photon coupling in 2D magnonics based hybrid quantum systems. We demonstrate strong magnon-photon coupling for both optical and acoustic magnon modes of an antiferromagnet.

Superconducting nanowires are very important due to their applications ranging from quantum technology to astronomy. In this work, we implement a non-invasive process to fabricate nanowires of high-Tc superconductor Bi2Sr2CaCu2O8+δ (BSCCO). We demonstrate that our nanowires can be used as bolometers in the visible range with very high responsivity of 9.7 × 103 V/W. Interestingly, in a long (30 μm) nanowire of 9 nm thickness and 700 nm width, we observe bias current dependent localized spots of maximum photovoltage. Moreover, the scalability of the bolometer responsivity with the normal state resistance of the nanowire could allow further performance improvement by increasing the nanowire length in a meander geometry. We observe phase slip events in nanowires with small cross-sections (12 nm thick, 300 nm wide, and 3μm long) at low temperatures. Our study presents a scalable method for realizing sensitive bolometers working near the liquid-nitrogen temperature.