Three small systems showing probable room-temperature superconductivity

Abstract

I shall discuss three small systems in which I think room-temperature superconductivity has been observed, in the hope that experimentalists will be persuaded to try to reproduce and extend results on some or all of the three systems mentioned. These are: 1. Narrow channels through films of oxidised atactic polypropylene (OAPP) and other polymers. 2. Some multiwalled carbon nanotubes or mats of nanotubes. 3. Sandwich structures based on CdF 2 . The main emphasis will be on polymer films. IntroductionSmall systems or systems with small subsystems are advantageous for superconductivity in two ways: First because it is easier to get Bose-Einstein condensation if there is separation in energy between the lowest state of the system and excited states; secondly because it is easier to get pairing at low carrier concentrations in low dimensions, since, in the BCS regime there is an enhanced density of states at low carrier concentrations in one and two dimensions compared with three, and, in the BEC regime because bipolarons can form more easily in low dimensions. The separation in energy between the ground state and excited states mentioned in the first point above is normally only a significant effect if the density of electronic states as a function of energy is such that condensation cannot occur in an infinite system, but in such cases it can have a large effect. For instance, for Bose condensation in small arrays of filaments if a simple quadratic dispersion is assumed for the bosons, then the condensation temperature at small lengths L can increase approximately as (1/L), as may be seen from Eqs. (21) and (2) of [1]. On the negative side it is not possible to get infinite conductivity in quasi one-dimensional systems because of phase slips, and only a small fraction of a Meissner effect is possible if the transverse dimensions are of the order of or smaller than the magnetic-field penetration depth. Also on the negative side, superconductivity in small systems will only have small-scale applications such as switching devices or interconnections in electronics, unless small systems

High-temperature superconductors: underlying physics and applications

“…Specifically, it can excite polarization waves inside the dielectric which have much higher frequencies than the Debye frequency. Consequently, surface superconductivity is expected with T c  102 − 104 K. These considerations have been taken up more recently by Eagles [41], who suggested probable RT superconductivity in small systems. The examples include CdF 2 -based sandwich structures embedded in boron doped layers.…”

High Temperature Superconductors: Materials and Applications

“…Therefore, the critical temperature for surface conductivity lies in the range of 102 -104 K. CdF2 originated sandwich structure consisted of boron inserted layers is the example of room temperature superconductors. For such type of superconductors at 319 K zero resistance was observed [8]. The diamagnetic susceptibility and resistivity were observed at 700 K transition temperature of carbon nanotubes [9].…”