Self-Doping and the Mott-Kondo Scenario for Infinite-Layer Nickelate Superconductors

We give a brief review of the Mott-Kondo scenario and its consequence in the recently-discovered infinite-layer nickelate superconductors. We argue that the parent state is a self-doped Mott insulator and propose an effective t- J-K model to account for its low-energy properties. At small doping, the model describes a low carrier density Kondo system with incoherent Kondo scattering at finite temperatures, in good agreement with experimental observation of the logarithmic temperature dependence of electric resistivity. Upon increasing Sr doping, the model predicts a breakdown of the Kondo effect, which provides a potential explanation of the non-Fermi liquid behavior of the electric resistivity with a power law scaling over a wide range of the temperature. Unconventional superconductivity is shown to undergo a transition from nodeless (d+is)-wave to nodal d-wave near the critical doping due to competition of the Kondo and Heisenberg superexchange interactions. The presence of different pairing symmetry may be supported by recent tunneling measurements.

Information-theoretic measures of superconductivity in a two-dimensional doped Mott insulator

A key open issue in condensed-matter physics is how quantum and classical correlations emerge in an unconventional superconductor from the underlying normal state. We study this problem in a doped Mott insulator with information-theory tools on the two-dimensional (2D) Hubbard model at finite temperature with cluster dynamical mean-field theory. We find that the local entropy detects the superconducting state and that the difference in the local entropy between the superconducting and normal states follows the same difference in the potential energy. We find that the thermodynamic entropy is suppressed in the superconducting state and monotonically decreases with decreasing doping. The maximum in entropy found in the normal state above the overdoped region of the superconducting dome is obliterated by superconductivity. The total mutual information, which quantifies quantum and classical correlations, is amplified in the superconducting state of the doped Mott insulator for all doping levels and shows a broad peak versus doping, as a result of competing quantum and classical effects.

The superconducting dome for holographic doped Mott insulator with hyperscaling violation

We reconsider the holographic model featuring a superconducting dome on the temperature-doping phase diagram with a modified view on the role of the two charges. The first type charge with density $$\rho _{A}$$ ρ A make the Mott insulator, and the second one with $$\rho _{B}$$ ρ B is the extra charge by doping, so that the complex scalar describing the cooper pair condensation couples only with the second charge. We point out that the key role in creating the dome is played by the three point interaction $$-c \chi ^{2} F_{\mu \nu }G^{\mu \nu }$$ - c χ 2 F μ ν G μ ν . The Tc increases with their coupling. We also consider the effect of the quantum critical point hidden under the dome using the geometry of hyperscaling violation. Our results show that the dome size and optimal temperature increase with z whatever is $$\theta $$ θ , while we get bigger $$\theta $$ θ for larger (smaller) dome depending on $$z>2$$ z > 2 ($$z<2$$ z < 2 ). We also point out that the condensate increases for bigger value of $$\theta $$ θ but for smaller value of z.

The Problem of a Lifetime

Anderson is the only theorist who answers questions at a news conference at the 1987 March Meeting of the American Physical Society (the “Woodstock of Physics”) where most physicists learned details about the newly discovered high-temperature cuprate superconductors, which lose all resistance at temperatures not very far below room temperature. He had just proposed a radical non-BCS theory which attributed superconductivity in these materials to a “resonating valence bond” description of a doped Mott insulator using a model first proposed by John Hubbard. He spent the next twenty years trying to convince his colleagues of the correctness of this theory, with only limited success.