Three studies in high-Tc cuprates

Abstract

We investigate three fundamental issues in the physics of high-Tc cuprates, from the perspective of a recently proposed comprehensive theory for these materials. a) Orbital Ordering × Superconductivity. The first issue is the detailed microscopic mechanism that produces an attractive interaction between holes in High-Tc cuprates. b) Dispersion Relation × Pseudogap Order Parameter. The second issue refers to the existence of a pseudogap order parameter, which would be different from zero all over the pseudogap phase and would vanish elsewhere. c) Chemical Potential × Quantum Critical Point Location. The third issue concerns the debate as to whether the quantum critical point, located where the pseudogap transition line T ∗ (x) meets the T = 0 axis is inside the superconducting dome or at its boundary. We obtain clearcut solutions for the three issues.

A testable theory for high-Tc superconductivity in cuprates

“…Such observables include: the critical SC transition temperature as a function of doping, T c (x), the pseudogap transition temperature as a function of doping, T * (x), the pressure dependence of the optimal SC transition temperature T max (P), the dependence of the optimal SC transition temperature on the number of CuO 2 layers, T max (N ), the resistivity as a function of temperature and magnetic field (ρ(T ) and ρ(H)) in the normal (non SC) phases and the spectral weight, among other observable quantities. All of these compare quite well with the experimental data for several cuprate materials [1][2][3][4] including LSCO, YBCO, Hg1201, Hg1212, Hg1223, Bi2201, Bi2212, Bi2213. Our theory is, therefore, testable and thus fulfills one of the first pre-requisites of any acceptable theory and, beyond that, it has proven to pass all the tests to which it has been submitted so far.…”

“…Such state has resonating spin zero dimers, similarly to the RVB state [8][9][10]. In our case, however, differently from the RVB state the resonating dimers are themselves Cooper pairs formed by two holes with opposite spins and belonging to different nearest neighbor sub-lattices [4].…”

“…We have successfully applied our theory in the explanation of the results of several experiments performed in the cuprates [1][2][3][4], hence our claim that our theory is not only testable: most importantly, it has passed the several tests to which it has been submitted so far.…”

“…An additional key ingredient of our theory is the fact that a dimerization occurs in the bipartite oxygen square lattice. Such dimerized configuration is energetically more favorable and is directly responsible for the onset of a superconducting state in the cuprates [4]. Such state has resonating spin zero dimers, similarly to the RVB state [8][9][10].…”

“…Almost all of them, however, failed in providing quantitative predictions that could be compared to the large amount of existing experimental data. Conversely, in a series of recent publications, [1][2][3][4] we have proposed a theory for High-Tc superconductivity in cuprates, which does not suffer from this shortcoming. Indeed, our theory makes several quantitative predictions, based on analytic expressions, for the outcome of measurements of physical observables in cuprates.…”