Scanning Tunneling Microscopy and spectroscopy on YBa2Cu3O7: new light on the subgap states

The mechanism underlying high temperature superconductivity continues to challenge our understanding. Scanning tunneling spectroscopy (STM) has historically been one of the prime techniques to tackle superconductivity in conventional BCS materials, providing key insight into the pairing mechanism. Here we present a new set of tunneling spectra obtained on YBCO single crystals. Our new results are twofold: Firstly, we have observed low energy electronic states that previously have been associated with the vortex core in HTS, to be present everywhere on the sample surface, both inside and outside vortices. This fact suggests that these features have a more general origin and are not specific signatures of the vortex core. Secondly, we have found these low energy states to be modulated in space, with a nematic order

Observation of Caroli–de Gennes–Matricon Vortex States in YBa₂Cu₃O_7-δ

The copper oxides present the highest superconducting temperature and properties at odds with other compounds, suggestive of a fundamentally different superconductivity. In particular, the Abrikosov vortices fail to exhibit localized states expected and observed in all clean superconductors. We have explored the possibility that the elusive vortex-core signatures are actually present but weak. Combining local tunneling measurements with large-scale theoretical modeling, we positively identify the vortex states in YBa2Cu3O7-δ. We explain their spectrum and the observed variations thereof from one vortex to the next by considering the effects of nearby vortices and disorder in the vortex lattice. We argue that the superconductivity of copper oxides is conventional, but the spectroscopic signature does not look so because the superconducting carriers are a minority

Vortex-core spectroscopy of <i>d</i>-wave cuprate high-temperature superconductors

The mechanism of high-temperature superconductivity remains one of the great challenges of contemporary physics. Here, we review efforts to image the vortex lattice in copper oxide-based high-temperature superconductors and to measure the characteristic electronic structure of the vortex core of a -wave superconductor using scanning tunneling spectroscopy

Conceptual Design Report for a Beta-Beam Facility

The Beta-Beam is a concept of large-scale facility that aims at providing pure electronic neutrino and antineutrino beams for the measurement of electron and muon neutrino oscillations. Beta-decaying nuclides are produced in large amounts in a facility of the scale of EURISOL, and are then post-accelerated and stored at large gamma in a racetrack decay ring. We present here a conceptual design of the accelerator chain of a Beta-Beam based at CERN