Radiation Effects, Superconductors

The effects of radiation on the properties of superconductors was the subject of the International Discussion Meeting held at Argonne National Laboratory, June 12-16, 1977. Eighty scientists from seven countries attended. The program focused on radiation effects on reversible and irreversible properties, fundamental fluxoid-defect interactions, radiation considerations for fusion magnets, and ion implantation in superconductors. 

The theory above has been applied in a variety of realistic situations. The range includes ionic conductance in aqueous solutions and molten alkali chlorides, damped spin-wave behaviour in paramagnetic systems, stimulated emission of radiation in masers, the fractional quantum Hall effect and quantum correlations in high-Tc cuprates and other non-BCS superconductors [4, 5, 7, 8, 14, 30]. In the next section we will also make some comments on the problem of long-range transcorrelations of protons in DNA [31]. 

The majority of studies using PR-TRMC in recent years have involved complex organic materials such as conjugated polymers or discotic liquid crystals. Inorganic semiconductor materials have however also received attention over the years. The first of these was a study of the radiation-induced conductivity in a powder sample of the high-Tc superconductor DyBajCujOj,. The superconductivity transition at 88 K on cooling was found to be accompanied by a dramatic, sudden increase in the radiation-induced conductivity an effect which... 

As we explore the interaction of cold-atom systems with microwave and terahertz radiation, we find that they have some unique properties as detectors. A comparison with superconductor-based detectors such as SQUlDs is instractive. Because of the third law of thermodynamics, i.e., a system in a single quantum state has zero entropy, the response of a SQUID is almost free of thermal noise. But an additional properly of SQUIDs is that they exhibit the phenomenon of coherence, i.e., wave interference, which leads to entirely new effects, e.g. the AC and DC Josephson effects. Cold atom clouds share this behavior, as we will discuss below. 

The Josephson effect is the phenomenon in which two superconducting materials weakly coupled through a non-superconducting interface show a sharp increase in conductance of current flowing from one of the superconductors to the other if radiation of a suitable frequency is applied to the interface. The relation between the voltage difference between the two superconductors Uj and the frequency / of the applied radiation for which there is an increase in current is given by... 

Coherent Synchrotron Radiation (CSR) has opened up the ability to perform measurements within the so-called THz-gap using this novel high-power THz and sub-THz source [13, 14]. Several facilities now offer a few days a year where the accelerator is run in a mode to specifically produce the short electron bunches required for CSR. One scientific area where this has been specifically exploited is the low-frequency study of novel superconductors. A high-flux synchrotron source allows a high accuracy in the detection of small effects in the reflectivity spectra and overcomes the problem of the very low intensity transmitted by these systems. 

Most electronic applications are based on the turmel effect between two superconductors that are separated by a weak (isolating) link that is only a few atomic layers thick. Currently, Nb and A1 are used preferably to build Josephson tunnel junctions (JTJs), whereas ceramic superconductors are stiU less common. However, the situation may soon change following the discovery of coherently emitting tera-Hertz radiation of intrinsic BSCCO JTJs (Ozyuzer et al., 2007). Some aspects of electronic applications are considered in detail at this point. 

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