Vladimir M. Krasnov — Page 2

arXiv2010

Observation of polaritons in Bi2Sr2CaCu2O8+x single crystals

The Bi2Sr2CaCu2O8+x high-temperature superconductor represents a natural metamaterial, composed of metallic CuO bilayers sandwiched between ionic BiO planes. Each pair of CuO bilayers forms an atomic-scale Josephson junction. Here we employ the intrinsic Josephson effect for in situ generation and detection of electromagnetic waves in Bi2Sr2CaCu2O8+x single crystals. We observe that electromagnetic waves form polaritons with several transverse optical phonons. This indicates the presence of unscreened polar response in cuprates, which may lead to strong electronphonon interaction. Our technique can provide intense local sources of coherent, monochromatic phonon-polaritons with kW/cm2 power densities.

cond-mat.supr-con↗

arXiv2010

Detection of the phase shift from a single quantized superconducting vortex

An Abrikosov vortex in a superconductor carries a flux quantum, Phi_0 = hc/2e, localized at its center, but induces a global 2pi phase rotation in the superconducting condensate. This long-range gauge field outside the area pierced by a magnetic field is due to the Aharonov-Bohm effect, which is a non-classical phenomenon that illustrates the significance of potentials rather than forces in quantum mechanics. In the London gauge, the phase of the condensate is given by the polar angle around the vortex. Here we raise the question whether this phase shift could be detected by means of Cooper pair interferometry using Josephson junctions as phase-sensitive detectors. We introduce a single Abrikosov vortex into a superconducting lead with a detector junction made at the edge of the lead. We observe that the vortex induces a Josephson phase shift equal to the polar angle of the vortex within the junction length. When the vortex is close to the junction it induces a pi-step in the Josephson phase difference, leading to a controllable and reversible switching of the junction into the 0 - pi state. This in turn results in an unusual Phi_0/2 quantization of the flux in the junction. The vortex may hence act as a tunable "phase battery" for quantum electronics.

cond-mat.supr-con↗