Q-ball mechanism of electron transport properties of high-T$_c$ superconductors
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Abstract
A theory is presented of a mechanism of high-Tc superconductivity in cuprates, based on the fact that 'nested' fermionic states near the Fermi surface of electrons/holes cause instability with respect to formation of the Q-balls (nontopological solitons) of coherently condensed spin/charge density wave fluctuations (SDW/CDW) with the wave-vector that matches the 'nesting' one. Simultaneously, the 'nested' fermions form superconducting condensate of Cooper/local pairs inside the Q-balls, with Q-ball SDW/CDW field being a 'pairing glue'. Thus, Q-balls possess lower total energy with respect to not condensed thermal SDW/CDW fluctuations and form a Q-balls 'gas' via first order phase transition below a temperature T$^*$. Besides, superconducting condensates inside the Q-balls induce a spectral gap on the nested parts of the Fermi surface, thus creating pseudogap phase. The Q-ball semiclassical field breaks chiral symmetry along the Matsubara time axis in Euclidean space-time possessing conserved Noether "charge" Q that makes the Q-ball volume finite. Prediction of the Q-ball scenario in cuprates is supported by micro X-ray diffraction data in HgBa$_2$CuO$_{4+y}$ in the pseudogap phase. The Q-balls of baryonic fields were originally predicted in Minkowski space-time by Sidney Coleman. In this paper it is demonstrated analytically that scattering of itinerant fermions on the Q-balls causes linear temperature dependence of electrical resistivity, that may explain famous 'Plankian' behavior in the 'strange metal' phase of high-Tc cuprates. Calculated diamagnetic response of Q-balls gas in the 'strange metal' phase and the phase diagram of high-Tc cuprates, with superconducting dome touching the 'strange metal' area at the optimal (holes)doping, are also in qualitative accord with experimental data.