Two-dimensional Fermi Gas Revisited

A number of authors have taken issue with the demonstration that the 2D Fermion gas with short-range repulsive interactions (and, of course, including spin) cannot be consistently treated as a renormalised quasiparticle system. This paper shows that the arguments given in some of these papers are invalid or irrelevant.Comment: 3 pages, no figure

The Charge-Spin Separated Fermi Fluid in the High Tc Cuprates: A Quantum Protectorate

We find experimental evidence for spin-charge separation in all four relevant phases of the cuprates. It is argued that this phenomenon serves to protect the properties of the cuprates from the effects of impurities and phonons.Comment: 2 figures included as jpg files. short version appeared in Science 288, 480 (2000

Bose Fluids Above Tc

This paper emphasizes that non-linear rotational or diamagnetic susceptibility is characteristic of Bose fluids above their superfluid Tcs. For sufficiently slow rotation or, for superconductors, weak B-fields this amounts to an incompressible response to vorticity. The cause is that there are terms missing in the conventionally accepted model Hamiltonian for quantized vortices in the Bose fluid. The resulting susceptibility can account for recent observations of Chan et al on solid He, and Ong et al on cuprate superconductors

Do We Need (or Want) a Bosonic Glue to Pair Electrons in Hiigh Tc Superconductors?

Many investigators have joined the search for a bosonic glue which is hypothecated to be the mechanism which binds the electron pairs in the cuprate high Tc superconductors, often referring to the Eliashberg formalism which was developed to reveal the role of phonons in the conventional polyelectronic metal superconductors. In this paper we point out that the picture of boson exchange is a folklore description of the pairing process with no rigorous basis. The problem of pairing is always that of evading the strong Coulomb vertex, the repulsive core of the interaction; we discuss the different means by which the two types of superconductors accomplish this feat

The Dilemma of Bose Solids: is He Supersolid?

Nearly a decade ago the old controversy about possible superfluid flow in the ground state of solid He4 was revived by the apparent experimental observation of such superflow. Although the experimentalists have recently retracted, very publicly, some of the observations on which such a claim was based, other confirming observations of which there is no reason for doubt remain on the record. Meanwhile theoretical arguments bolstered by some experimental evidence strongly favor the existence of supersolidity in the Bose-Hubbard model, and these arguments would seem to extend to solid He. The true situation thus is apparently extraordinarily opaque. The situation is complicated by the fact that all accurate simulation studies on Heuse the uniform sign hypothesis which confines them to the phase-coherent state, which is, in principle, supersolid, so that no accurate simulations of the true, classical solid exist. There is great confusion as to the nature of the ground state wave-function for a bose quantum solid, and we suggest that until that question is cleared up none of these dilemmas will be resolved

Anomalous Magnetothermal Resistance of High-Tc Superconductors: Anomalous Cyclotron Orbits at a Dirac Point

I derive equations of motion for quasiparticles near the nodes in the d-wave gap of high Tc superconductors. Previous versions have not properly taken into account the spatial dependence of the gap parameter phase. The results are compatible with magnetothermal conductivity measurements in the superconducting phase by Ong and Krishana.Comment: 11 pages, 3 Figures (figures not included but hard copies available on reques

Physics of the Pseudogap II: Dynamics, Incompressibility, and Fermi Arcs as Motional Narrowing

A further discussion of the vortex fluid in the cuprate high Tc superconductors is presented. The crucial property of incompressibility towards the addition of net vorticity, leading to the marked nonlinearity of the response functions, is justified from first principles. We also discuss the Fermi Arc phenomenon of Campuzano as a consequence of the time-fluctuating phase in the vortex fluid

The ground state of the bose-hubbard model is a supersolid

The Bose-Hubbard model is well-defined description of a Bose solid which may be realistic for cold atoms in a periodic optical lattice. We show that contrary to accepted theories it can never have as a ground state a perfect Mott insulator solid and that it has a low-energy spectrum of vortex-like phase fluctuations. Whether the ground state is necessarily commensurate remains an open question

Why not a superfluid solid?

The question of whether a Bose solid can have a superfluid fraction in the absence of interstitials, holes or other defects is discussed. An unlikely scenario which may accommodate this possibility is proposed, based on a Hartree-Fock treatment of the quantum solid. It is now believed that this version is correctComment: arXiv admin note: significant text overlap with arXiv:cond-mat/050473

Dynamics of the Vortex Fluid in Cuprate Superconductors: the Nernst Effect

We calculate the Nernst effect in the vortex fluid phase, which occurs in the lower-T portion of the pseudogap region of the high Tc cuprate phase diagram. The dynamics is dominated by the flows due to both thermally excited vortices and those caused by the magnetic field; we show that the flow of the latter due to the thermal gradient encounters a viscous force caused by the random vortex flows. The temperature and field dependence is controlled by the effects of T and B on the momentum-dependent energy gaps and thence on the superfluid density. A reasonable level of agreement with the observational data is obtained, in view of the crudity of the assumptions