Dependence of Superconducting Transition Temperature on the Electron-Magnon, Electron-Phonon and Electron-Electron Interactions in a Heavy Fermion System

Abstract

An explicit expression for the superconducting critical temperature, T_c, in a heavy fermion superconductor has been derived considering the presence of attractive electron-magnon and electron-phonon interactions, and repulsive residual electron-electron interaction responsible for superconductivity in these materials, using the generalized BCS gap equation. The dependence of T_con these interactions is quite involved, but the observed value of T_cin CeCu₂Si₂, for example, can be explained using realistic physical parameters specifying the different interactions.

Indexing terms:

• Superconductivity
• Generalised BCS equation
• Heavy Fermion system
• CeCu₂Si₂
• Kondo effect
• Electron-magnon
• Electron-electron and Electro-phonon interaction

Additional information

Notes on contributors

S P Tewari

S P Tewari, is a Professor of Physics in the Department of Physics and Astrophysics, University of Delhi, Delhi for the last over twelve years. He has been involved in all kinds of academic activities like teaching, research, supervising research work leading to the award of PhD degrees, organizing Symposia and Conferences, presenting research work at various International and National Symposia and Conferences in the form of invited talks, presentations and chairing the sessions etc since he joined as a Faculty member of Delhi University almost thirty years ago. He has published well over hundred research papers in the top class International reputed journals of physics in different branches of Condensed Matter Physics like superconductivity: both high temperature (rare earth cuprates, Cheveral phase, heavy fermions and fullerides) and conventional, strongly coupled superconductors; density—density distinct and auto—correlation functions, in ordered (highly anisotropic crystals, proteins, bio-polymers, fullerites etc) and disordered (polymers and liquids) materials; frequency and wave—vector dependent electron dielectric functions in solid state plasma at different densities ranging from highly degenerate (metallic) to non-degenerate state (semiconductors); thermal neutron scattering, transport and production of intense beam of cold neutrons from hydrogenous condensed systems; different properties of recently discovered crystalline form of fullerene-fullerite—the third allotrope of carbon, etc.

Prof Tewari is co-editor of two research level books and has co-authored five books; two of which have been published by NCERT, New Delhi and one by CSIR New Delhi, in its Golden Jubilee series.

Prof S P Tewari was visiting Professor of Physics at Northwestern University, USA (1971–72) and Commonwealth Academic Staff Fellow at Bristol University, UK (1978–79). He has been consultant and senior participant etc in different activities of International Center for Theoretical Physics (ICTP) Trieste, Italy. He has also visited many other countries in connection with his research activities.

Charu Kapoor

Charu Kapoor's interest is related to in the study of recently discovered peculiar intermetallic compounds commonly referred to as “heavy fermion” systems. These materials carry two types of electrons: mobile metallic and localized f-electrons. Further, one of the atomic constituents is magnetic in character. Because of these, the electron elementary excitation in these systems turn out to be quite heavy. The effective mass of elementary excitation is a few hundred times the mass of ordinary electron.

Dr Kapoor has solved the problem of self-energy of such an electron excitation due to electron-phonon interaction and has also investigated, rather deeply, the formation of Cooper pair and bulk superconductivity. The effect of magnetic elementary excitation; magnons, on superconductivity in these materials has also been studied. She has published several papers on the above topics in international journals of repute. Her work has also been presented in both national and international conferences.

Dr Charu Kapoor is at present teaching in the University of Delhi, Ramjas College, and is also actively involved in furthering her research pursuits.