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Superconductivity in cuprates is achieved by doping holes into a correlated charge-transfer insulator. While the correlated character of the parent insulator is now understood, there is no accepted theory for the normal state of the doped insulator. I present a mostly empirical analysis of a large range of experimental characterizations, making the case for two pseudogaps: (1) a large pseudogap resulting from the competition between the energy of superexchange-coupled local Cu moments and the kinetic energy of doped holes; (2) a small pseudogap that results from dopant disorder and consequent variations in local charge density, leading to a distribution of local superconducting onset temperatures. The large pseudogap closes as hole kinetic energy dominates at higher doping and the dynamic antiferromagnetic correlations become overdamped. Establishing spatially-homogeneous $d$-wave superconductivity is limited by those regions with the weakest superconducting phase coherence, which tends to be limited by low-energy spin fluctuations. The magnitude of the small pseudogap is correlated with the doping-dependent energy $E_{rm cross}$ associated with the neck of the hour-glass dispersion of spin excitations. The consequences of this picture are discussed.
Evidence from NMR of a two-component spin system in cuprate high-$T_c$ superconductors is shown to be paralleled by similar evidence from the electronic entropy so that a two-component quasiparticle fluid is implicated. We propose that this two-compo
Geometrical Berry phase is recognized as having profound implications for the properties of electronic systems. Over the last decade, Berry phase has been essential to our understanding of new materials, including graphene and topological insulators.
The origin of the exceptionally strong superconductivity of cuprates remains a subject of debate after more than two decades of investigation. Here we follow a new lead: The onset temperature for superconductivity scales with the strength of the anom
A universal scaling relation, $rho_s propto sigma(T_c)times T_c$ has been reported by Homes $et$ $al$. (Nature (London) {bf 430}, 539 (2004)) where $rho_s$ is the superfluid density and $sigma(T)$ is the DC conductivity. The relation was shown to app
This paper addresses the transition from the normal to the superfluid state in strongly correlated two dimensional fermionic superconductors and Fermi gases. We arrive at the Berezinskii-Kosterlitz-Thouless (BKT) temperature $T_{text{BKT}}$ as a func