Electron-phonon interaction in nanostructures at sub-Kelvin temperatures

2^nd International Conference and Exhibition on Mesoscopic and Condensed Matter Physics

October 26-28, 2016 Chicago, USA

Dragos Victor Anghel and George Alexandru Nemnes

Institutul National de Cercetare-Dezvoltare pentru Fizica si Inginerie Nucleara Horia Hulubei, Romania

Scientific Tracks Abstracts: J Material Sci Eng

Abstract :

We revisit the Bardeen-Cooper-Schriefer (BCS) theory of superconductivity by studying the effect of the asymmetry of the attraction band with respect to the chemical potential, on the physical properties of the superconductor. The attraction band is defined as the interval in which the pairing interaction is manifested. Although in the standard BCS formalism â��the center of the attraction bandâ��is identified with the chemical potential, this represents only a convenient choice and not a physical constraint. Since the chemical potential and the attraction band may be influenced differently by the external conditions (e.g. pressure) or preparation methods (e.g. changing the mobility band by changing the chemical composition of the superconductor), it is natural to assume that is not identical to the chemical potential. Therefore, in our study we denote the chemical potential of the system by and we analyze the effect of the difference on the physical properties of the superconductor. We find that if the energy gap �� and the temperature of the superconductornormal metal phase transition Tph change; the ratio ��(T=0)/Tph changes also with (see Fig. 1). More dramatically, when �¼â� �¼R, a population imbalance appears in equilibrium and the superconductor-normal metal phase transition becomes of the first order. If varies monotonically with pressure or doping, then a feature like the superconducting dome appears when the temperature of the phase transition is plotted vs. pressure or doping concentration. Fig. 1: The energy gap as a function of temperature, for different values of . ��0 and Tc are the energy gap at zero temperature and the critical temperature in the standard BCS theory. The superconductor-normal metal phase transition occurs when �� jumps to 0.

Biography :

Dragos Victor Anghel is a Senior Scientist (1st grade) at Horia Hulubei National Institute of Physics and Nuclear Engineering in Romania. His research interests are theoretical condensed matter physics, mesoscopic physics, nanoscopic detectors and complex systems.

Email: dragos@theory.nipne.ro