Response functions,superconductivity and ferromagnetism in the many fermion system |
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| Affiliation: | 1. Faculty of Physics, Technion – Israeli Institute of Technology, Haifa 32000, Israel;2. Israel Atomic Energy Commission, P.O. Box 7061, Tel-Aviv 61070, Israel;3. Physics Department, Nuclear Research Centre-Negev, P.O. Box 9001, Beer Sheva 84190, Israel;4. Department of Materials Science and Engineering, Drexel University, Philadelphia, PA 19104, United States;5. Helmholtz-Zentrum Berlin fur Materialen und Energie, Hahn-Meitner Platz 1, D-14109, Berlin, Germany;6. Racah Institute of Physics, Hebrew University of Jerusalem, 91904 Jerusalem, Israel;1. JST CREST, Gobancho 7, Chiyoda-ku, Tokyo 102-0076, Japan;2. Department of Materials Science, Osaka Prefecture University, Gakuen-cho 1-1, Naka-ku, Sakai 599-8531, Japan;3. Department of Nanomechanics, School of Engineering, Tohoku University, Aoba 6-6-01, Aramaki, Aoba-ku, Sendai 980-8579, Japan;4. Department of Materials Science and Engineering, Delft University of Technology, Mekelweg 2, 2628 CD Delft, The Netherlands;1. Department of Physics and Astronomy, Rutgers University, Piscataway, NJ 08856, United States;2. Brookhaven National Laboratory, NY, United States;1. Middle East Technical University, Department of Physics, Ankara, 06800, Turkey;2. Department of Electric and Energy, Ahi Evran University, Kirsehir, 40100, Turkey;3. Hacettepe University, Department of Physics Engineering, Ankara, 06800, Turkey;4. Pamukkale University, Department of Physics, Denizli, 20020, Turkey;5. School of Physical Science and Technology, Southwest University, Chongqing, 400715, China;6. Department of Electrical and Electronics Engineering, Atilim University, Ankara, 06836, Turkey |
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| Abstract: | At the phase transition, the anomalies of thermodynamic and static response functions coincide due to the fact that the free energy, expressed in terms of response functions at imaginary frequency including zero, has its pole at zero frequency. Previous work has considered the singularities which arise from the polarisation of the medium. In this paper, a study is made of the divergences arising from the modification of the vertex function. The diamagnetic current is related to the free energy via the Ward Identity so that the specific heat anomaly inevitably gives rise to the Meissner effect. Below the transition the system adjusts to the singularity by going into the BCS condensed state. The similarity between BCS theory and ferromagnetism is shown both through a Weiss field approach and diagrammatically by including special correlations between k and -k. Its importance for an understanding of the broken symmetry problem is discussed. Finally, the parallel behaviour of the susceptibility and specific heat of a Bloch ferromagnet is demonstrated. |
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