Evidence for thermal activation in the glassy dynamics of insulating granular aluminum conductance

Insulating granular aluminum is one of the proto-typical disordered insulators whose low temperature electrical conductance exhibits ubiquitous non-equilibrium phenomena. These include slow responses to temperature or gate voltage changes, characteristic field effect anomalies and ageing phenomena typical of a glass. In this system the influence of temperature on the glassy dynamics has remained elusive, leading to the belief that the slow relaxations essentially proceed via elastic quantum tunneling. A similar situation was met in insulating indium oxide and it was concluded that in high carrier density Anderson insulators, electrons form a quantum glass phase. In this work we experimentally demonstrate that thermal effects do play a role and that the slow dynamics in granular aluminum is subject to thermal activation. We show how its signatures can be revealed and activation energy distributions can be extracted, providing a promising grasp on the nature of the microscopic mechanism at work in glassy Anderson insulators. We explain why some of the experimental protocols previously used in the literature fail to reveal thermal activation in these systems. Our results and analyses call for a reassessment of the emblematic case of indium oxide, and question the existence of a quantum glass in any of the systems studied so far

Control of Coulomb blockade in a mesoscopic Josephson junction using single electron tunneling

We study a circuit where a mesoscopic Josephson junction (JJ) is embedded in an environment consisting of a large bias resistor and a normal metal - superconductor tunnel junction (NIS). The effective Coulomb blockade of the JJ can be controlled by the tunneling current through the NIS junction leading to transistor-like characteristics. We show using phase correlation theory and numerical simulations that substantial current gain with low current noise ($i_{n}\lesssim 1$ fA/$\sqrt{\text{Hz}}$) and noise temperature ($\lesssim$ 0.1 K) can be achieved. Good agreement between our numerical simulations and experimental results is obtained.Comment: 5 pages, 4 figures, RevTE

Extending the applicability of an open-ring trap to perform experiments with a single laser-cooled ion

An open-ring ion trap, also referred to as transparent trap was initially built up to perform $\beta$-$\nu$ correlation experiments with radioactive ions. This trap geometry is also well suited to perform experiments with laser-cooled ions, serving for the development of a new type of Penning trap, in the framework of the project TRAPSENSOR at the University of Granada. The goal of this project is to use a single $^{40}$Ca$^+$ ion as detector for single-ion mass spectrometry. Within this project and without any modification to the initial electrode configuration, it was possible to perform Doppler cooling on $^{40}$Ca$^+$ ions, starting from large clouds and reaching single ion sensitivity. This new feature of the trap might be important also for other experiments with ions produced at Radioactive Ion Beam (RIB) facilities. In this publication, the trap and the laser system will be described, together with their performance with respect to laser cooling applied to large ion clouds down to a single ion.Comment: 9 pages, 13 figure

Slow Conductance Relaxation in Insulating Granular Al: Evidence for Screening Effects

It is shown that the conductance relaxations observed in electrical field effect measurements on granular Al films are the sum of two contributions. One is sensitive to gate voltage changes and gives the already reported anomalous electrical field effect. The other one is independent of the gate voltage history and starts when the films are cooled down to low temperature. Their relative amplitude is strongly thickness dependent which demonstrates the existence of a finite screening length in our insulating films and allows its quantitative estimate (about 10nm at 4K). This metallic-like screening should be taken into account in the electron glass models of disordered insulators

Determination of characteristic relaxation times and their significance in glassy disordered insulators

We revisit the field effect procedure used to characterise the slow dynamics of glassy Anderson insulators. It is shown that in the slowest systems the procedure fails and the "characteristic" time values extracted are not intrinsic but determined by the experimental procedure itself. In other cases (like lightly doped indium oxide) qualitative indications about the dynamics might be obtained, however the times extracted cannot be seen as characteristic relaxation times of the system in any simple manner, and more complete experiments are necessary. Implications regarding the effect of carrier concentration on the emergence of glassiness are briefly outlined.Comment: published with minor proof correction

Metallicity of the SrTiO3 surface induced by room temperature evaporation of alumina

It is shown that a metallic state can be induced on the surface of SrTiO3 crystals by the electron beam evaporation of oxygen deficient alumina or insulating granular aluminium. No special preparation nor heating of the SrTiO3 surface is needed. Final metallic or insulating states can be obtained depending on the oxygen pressure during the evaporation process. Photoconductivity and electrical field effect are also demonstrated.Comment: 8 pages, 3 figure

Ipopv2: Photoionization of Ni XIV -- a test case

Several years ago, M. Asplund and coauthors (2004) proposed a revision of the Solar composition. The use of this new prescription for Solar abundances in standard stellar models generated a strong disagreement between the predictions and the observations of Solar observables. Many claimed that the Standard Solar Model (SSM) was faulty, and more specifically the opacities used in such models. As a result, activities around the stellar opacities were boosted. New experiments (J. Bailey at Sandia on Z-Pinch, The OPAC consortium at LULI200) to measure directly absorbtion coefficients have been realized or are underway. Several theoretical groups (CEA-OPAS, Los Alamos Nat. Lab., CEA-SCORCG, The Opacity Project - The Iron Project (IPOPv2)) have started new sets of calculations using different approaches and codes. While the new results seem to confirm the good quality of the opacities used in SSM, it remains important to improve and complement the data currently available. We present recent results in the case of the photoionization cross sections for Ni XIV (Ni13+ ) from IPOPv2 and possible implications on stellar modelling.Comment: 10 pages, 3 figures, Conf. on New Advances in Stellar Physics: From Microscopic to Macroscopic Processe

Design Issues of TeV Linear Colliders

Within the frame work of a world-wide collabora-tion, various possible approaches for Linear Colliders in the TeV energy range (TLC) and high luminosity (~ 1034 cm-2 sec-1) are explored in different laboratories and periodically compared in international workshops. The main accelerator physics issues required to meet the requested performance improvement by three orders of magnitude in luminosity and by a factor 10 in beam energy with respect to the unique linear collider presently operational, the SLC at SLAC, are reviewed, pointing out the main challenges common to all designs as well as the possible technological choices. Corresponding designs based on the improve-ment of present standard or the development of new tech-nologies are presented, emphasizing their main issues and specific challenges. The main goals of ambitious test facilities presently set-up to study the feasibility and cost of the various schemes in the next few years are introduced

A Review of Possible Future High-Energy Colliders for the Post-LHC Era

A review of the studies being conducted by various laboratories and collaborations in order to determine and optimise the next generation of particle accelerators for physics at the high energy frontier beyond HERA1) at DESY, LEP2) and LHC3) at CERN, SLC4) at SLAC and the TEVATRON5) at FNAL is presented. The relative advantages of the Very Large Hadron Colliders, Electron Positron Colliders and Muon Colliders are compared pointing out their main challenges and key issues both in beam dynamics and technology. The present status and future plans of the studies are summarised outlining the research and development of key components and their tests in ambitious test facilities. Finally, the schedules presently assumed and the possible scenarios for the post-LHC-era around 2010 are presented