Related papers: Quantum String Liquid State in LaOFeAs and Superco…
Several ideas that have been shown to apply to superconductors and the cuprates in particular are joined together to form a mechanism for high temperature superconductivity. The mechanism is basically a weak BCS(1)type coupling between the…
Two-dimensional (2D) strongly correlated electron systems underlie many of the most important phenomena in contemporary condensed matter physics, including the Quantum Hall Effect (QHE), ``high T_c'' superconductivity, and possible exotic…
We study one dimensional wires with spin-orbit coupling. We show that in the presence of Zeeman field and strong electron-electron interaction a clean wire may form fractional helical liquid states with phenomenology similar to fractional…
We consider possible routes to superconductivity in hydrated cobaltates Na_xCoO_2.yH_2O on the basis of the t-J-V model plus phonons on the triangular lattice. We studied the stability conditions for the homogeneous Fermi liquid (HFL) phase…
The superconducting metal-organic framework Cu-BHT forms a kagome lattice with metals at the vertices and ligands along the bonds. This bipartite motif is common in reticular materials. We show that a tight-binding model on this lattice…
An understanding of spin excitations in cuprates is essential since the mechanism of high-T$_C$ superconductivity might be linked to spin fluctuations. Band calculations for long "1-dimensional" unit cells of La$_2$CuO$_4$ show that the…
The iron-based LaFeAsO$_{1-x}$F$_x$ recently discovered by Hosono's group is a fresh theoretical challenge as a new class of high-temperature superconductors. Here we describe the electronic structure of the material and the mechanism of…
A unified theory is outlined for the cuprates, Fe-based, and related superconductors. Their low-energy excitations are approached in terms of auxiliary particles representing combinations of atomic-like electron configurations, and the…
Quantum spin liquid is a nontrivial magnetic state of longstanding interest, in which spins are strongly correlated and entangled but do not order1, 2; further intriguing is its doped version, which possibly hosts strange metal and…
The understanding of the interplay between different orders in a solid is a key challenge in highly correlated electronic systems. In real systems this is even more difficult since disorder can have a strong influence on the subtle balance…
Very recently a new family of layered materials, containing BiS2 planes was discovered to be superconducting at temperatures up to Tc=10 K, raising questions about the mechanism of superconductivity in these systems. Here, we present…
The effect of a quantum phase transition associated with the appearance of the fermion condensate in an electron liquid on the properties of superconductors is considered. It is shown that the electron system in both superconducting and…
In elemental metals the pairing of electrons leading to superconductivity is mediated by the vibrations of the crystal lattice and the pairs have spherical symmetry. For layered organic molecular crystals there is no consensus about the…
Symbiotic solitons (SS) and quantum droplets (QD) are self-trapped localized modes emerging in binary Bose-gas mixtures with intra-component repulsion and inter-component attraction. We have shown that two-dimensional SS can be stabilized…
Motivated by the recent discovery of superconductivity in two dimensional CoO$_2$ layers, we present some possibly useful results of the RVB mean field theory applied to the triangular lattice. Away from half filling, the order parameter is…
We analyze the t-J model on a square lattice using bosonic spinons and fermionic holons for low density x of holes. Spinons are paired into singlets, which condense below a temperature T*. The condensate evolves out of the Mott phase -…
High resolution photoemission measurements have been carried out on non-superconducting LaOFeAs parent compound and various superconducting R(O1-xFx)FeAs (R=La, Ce and Pr) compounds. We found that the parent LaOFeAs compound shows a…
We present a valence transition model for electron- and hole-doped cuprates, within which there occurs a discrete jump in ionicity Cu$^{2+} \to$ Cu$^{1+}$ upon doping, at or near optimal doping in the electron-doped compounds and at the…
Lifting supersymmetric quantum mechanics to loop space yields the superstring. A particle charged under a fiber bundle thereby turns into a string charged under a 2-bundle, or gerbe. This stringification is nothing but categorification. We…
An anomalously high valence state sometimes shows up in transition-metal oxide compounds. In such systems, holes tend to occupy mainly the ligand $p$ orbitals, giving rise to interesting physical properties such as superconductivity in…