The phonon contribution to the phenomenon of high temperature superconductivity in the cuprates is argued as being masked as polarons generated by the polarization of the charge reservoir accompanying the Jahn-Teller tilting of the apical oxygen. We discuss the Mahan oscillator-spring extension model as an analogy to the charge reservoir-CuO plane -axis polarons. Using the Boltzmann kinetic equation, we show that the polaron dissociates or collapses at a temperature corresponding to the critical temperature of the superconductor. 1. Introduction Almost three decades since the discovery of high temperature superconductivity in the cuprate La-Ba-CuO by Bednorz and Muller [1] and subsequently in many CuO based compounds by other researchers, there is still no closure about the mechanism of superconductivity in these systems [2, 3]. One of the major points of disagreement is whether phonons contribute along with the accepted spin magnetic fluctuation to the high critical temperature of the cuprates. Many researchers are in support of the phonon mechanism as the only factor responsible for the cuprates high critical temperatures [4–6]. Other workers [7–9] have considered the spin magnetic fluctuation the only adoptable theory for the cuprates. A good reason for the persistence of the “phonon-camp,” is perhaps the enduring success of the electron-phonon interaction (EPI) explanation of the low temperature superconductivity (LTS) by Bardeen, Cooper, and Schrieffer (BCS), [10]. Still another reason may be the recent discovery of superconductivity in MgB3 at ?K [11]; this being explained surprisingly by the EPI mechanism. It has even become very comfortable to make prognosis of still higher ’s in materials whose electronic properties are well understood based on the EPI. As an example we mention the EPI mechanism used by Gao and his coworkers to predict that the compound Li2B3C superconducts at about 50?K through the process of lifting the -bonding up above the Fermi level by doping, enabling -electrons to interact strongly with the lattice vibrations in such a way that electron pairing occurs [12]. In the LTS such as lead, tin, and aluminium, phonon contribution is indicated by the isotope effect which relates the critical temperature ( ) to the mass ( ) of the isotope atom as , where is the electron-phonon coupling constant defined as . The BCS value for is [13] which corresponds to the weak coupling regime where the Coulomb interaction is neglected. When the Coulomb interaction is taken into account, can be approximated by , where and is the BCS interaction
References
[1]
J. G. Bednorz and K. A. Müller, “Possible high Tc superconductivity in the Ba-La-Cu-O system,” Zeitschrift für Physik B, vol. 64, no. 2, pp. 189–193, 1986.
[2]
M. V. Sadovsky, “Models of the pseudogap state in high-temperature superconductors,” http://arxiv.org/abs/cond-mat/0408489.
[3]
G. Sica, G. H. Samson, and A. S. Alexandrov, “Pseudogap in high-temperature superconductors from realistic Fr?hlich and Coulomb interactions,” http://arxiv.org/abs/1208.0240.
[4]
M. L. Kulic, “Electron phonon interaction and strong correlations in high-temperature superconductors: one can not avoid unavoidable,” http://arxiv.org/abs/cond-mat/0404287.
[5]
A. S. Alexandrov and J. T. Devreese, Advances in Polaron Physics, Springer, Berlin, Germany, 2010.
[6]
E. G. Maksimov, “The problem of high-temperature superconductivity. Present situation,” Uspekhi Fizicheskikh Nauk, vol. 170, pp. 1033–1061, 2000.
[7]
N. M. Plakida, “Spin excitations and mechanisms of superconductivity in cuprates,” http://arxiv.org/abs/1110.6715.
[8]
N. Bulut, D. J. Scalapino, and R. T. Scalettar, “Nodeless d-wave pairing in a two-layer Hubbard model,” Physical Review B, vol. 45, no. 10, pp. 5577–5584, 1992.
[9]
P. Prelovsek, I. Sega, A. Ramsak, and J. Bonca, “Spin fluctuations in cuprates as the key to high Tc,” http://arxiv.org/abs/cond-mat/0601511.
[10]
J. Bardeen, L. N. Cooper, and J. R. Schrieffer, “Theory of superconductivity,” Physical Review, vol. 108, no. 5, pp. 1175–1204, 1957.
[11]
T. Muranaka and J. Akimitsu, “Superconductivity in MgB2,” Zeitschrift für Kristallographie, vol. 226, no. 4, pp. 385–394, 2011.
[12]
M. Gao, Z. Y. Lu, and X. Tao, “Prediction of phonon-mediated high temperature superconductivity in stoichiometric Li2B3C,” http://arxiv.org/abs/1307.1323.
[13]
J. R. Schrieffer, Theory of Superconductivity, Benjamin, New York, NY, USA, 1964.
[14]
A. S. Davydov, “Theoretical investigation of high-temperature superconductivity,” Physics Report, vol. 190, no. 4-5, pp. 191–306, 1990.
[15]
V. H. Crespi and M. L. Cohen, “Anharmonic phonons and high-temperature superconductivity,” Physical Review B, vol. 48, no. 1, pp. 398–406, 1993.
[16]
A. S. Mishenko, “Electron-phonon interaction in the undoped high temperature superconductors,” Uspekhi Fizicheskikh Nauk, vol. 179, pp. 1259–1280, 2009.
[17]
L. D. Landau, “On the motion of electrons in a crystal lattice,” in Collection of Works of L.D. Landau, E. M. Lifshitz, Ed., Nauka, Moscow, Russia, 1933.
[18]
A. E. Anselm, Introduction to Semiconductor Theory, Nauka, Moscow, Russia, 1978.
[19]
H. Frohlich, “Interactions of electrons with lattice vibrations,” Proceedings of the Royal Society A, vol. 215, pp. 291–298, 1952.
[20]
R. P. Feynman, Statistical Mechanics, Benjamin, New York, NY, USA, 1972.
[21]
M. Zoli, “Polaron mass and electron-phonon correlations in the Holstein model,” Advances in Condensed Matter Physics, vol. 2010, Article ID 815917, 15 pages, 2010.
[22]
E. N. Myasnikov, A. E. Myasnikova, and F. V. Kusmartsev, “Coherence of the lattice polarization in large-polaron motion,” Physical Review B, vol. 72, no. 22, Article ID 224303, 11 pages, 2005.
[23]
A. S. Davydov and V. Z. Enolsky, “Effective mass of the Pekar polaron,” Zhurnal Eksperimental noi i Teoreticheskoi Fiziki, vol. 94, pp. 177–181, 1988.
[24]
J. T. Devreese, “Polarons,” http://arxiv.org/abs/cond-mat/0004497.
[25]
D. J. Scalapino, E. Loh Jr., and J. E. Hirsch, “Fermi-surface instabilities and superconducting d-wave pairing,” Physical Review B, vol. 35, no. 13, pp. 6694–6698, 1987.
[26]
D. J. Scalapino, “Superconductivity and spin fluctuations,” http://arxiv.org/abs/cond-mat/9908287.
[27]
G. D. Mahan, Many-Particle Physics, Kluwer/Plenum, New York, NY, USA, 1990.
[28]
C. Kittel, Quantum Theory of Solids, John Wiley & Sons, New York, NY, USA, 1987.
[29]
L. D. Landau and S. I. Pekar, “The effective mass of the polaron,” in Collected Works of L.D. Landau, E. M. Lifshitz and I. M. Khalatnikov, Eds., vol. 2, pp. 47–53, Nauka, Moscow, Russia, 1948.
[30]
A. Mourachkine, Room Temperature Superconductivity, University of Cambridge, Cambridge, UK, 2004.