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Philip W Anderson

Publications and source records attributed to Philip W Anderson.

17 recordsLinked to original sources
arXiv2018

Four Last Conjectures

I collect here some ideas on four topics which have not gained much acceptance in the community. Hence, i call them conjectures. The first three of these are in my area of expertise, and I personally consider them to be verified, if by evidence some others might find less than convincing. On the the fourth I do not claim expert knowledge but it has not been refuted in any way that I understand. The first is the proposition that the ground state of a solid made up of simple bosons is phase coherent and sustains overlap currents. The second proposes that the cuprate superconductors upper phase transition is into an Ong vortex liquid phase which quantizes flux and consequently exhibits a characteristic singular, nonlinear diamagnetic behavior. The third proposes that the metallic phase of the doped Mott insulator, if it has a Fermi surface, has deep entanglement and an orthogonality catastrophe causing a Fermi surface singularity. This manifests itself as the strange metal of the cuprate phase diagram. The fourth conjecture is that the dark energy in cosmology models is the consequence at least in part of gravitational radiation carrying energy past us.

cond-mat.supr-con↗
arXiv2016

Last Words on the Cuprates

Much of what I have to say in the following (not all) is contained in my Informal History published in 2010 in the Intl Journ of Mod Phys and available as arXiv:1011.2736 [cond-mat]. But because the literature on the subject continues to burgeon, mostly without much if any reference to the fundamentals that I laid out in that article, I think it is time to distribute a summary of the conclusions I reached in that article, as well as a few newer thoughts.

cond-mat.supr-con↗
arXiv2013

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.

cond-mat.stat-mech↗
arXiv2011

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.

cond-mat.quant-gas↗
arXiv2010

Personal history of my engagement with cuprate superconductivity, 1986-2010

Six months ago I was asked to write a personal history of my engagement with the high-Tc problem of the cuprate superconductors, in rather informal and autobiographical style. As the work proceeded I realized that it was impossible and would have been dishonest to separate out my rather amusing but seminal early fumblings from the complete restructuring of the problem which I have achieved during the past decade. But the result became considerably too long, by over half, for its intended recipient. The assignment had left me with no obligation to deal with all the fascinating but irrelevant phenomenology which I had more or less instinctively ignored on my way, but that feature also fails to endear the article to any conceivable editorial board containing knowledgeable experts on the subject. Also, their purpose was for it to serve as a (quote) introduction to the more technical debates, but its message is that almost all of these are not relevant. They are not, on the whole, focused on achieving understanding of the crucial experimental anomalies, many, if not most, of which are now understood. The key to the problem is a new method of dealing with the constrained Hilbert space which follows from the necessity of Gutzwiller projection.

cond-mat.supr-con↗
arXiv2009

Transport Anomalies of the Strange Metal: Resolution by Hidden Fermi Liquid Theory

The strange metal phase of optimally and overdoped cuprates exhibits a number of anomalous transport properties: unsaturating linear T resistivity, distinct relaxation times for Hall angle and resistivity, temperature dependent anisotropic relaxation times, and a characteristic crossover from supposed Fermi Liquid to linear T behavior. All receive natural explanations and quantitative fits in terms of the Hidden Fermi Liquid theory.

cond-mat.str-el↗
arXiv2009

Incoherent Tunneling Amplitude in High Tc Cuprates

A 2004 paper of Anderson and Ong calculated the asymmetric coherent spectrum of point-contact tunneling into a Gutzwiller-projected superconductor. We here correct some details of that paper and present recipes for the manyquasiparticle, incoherent spectrum, the major portion of which results from the spin-flip decay of the injected quasiparticle. An illustrative example is shown.

cond-mat.supr-con↗
arXiv2008

A Gross-Pitaevskii Treatment for Supersolid He

The observations of non-linear rotational susceptibility (NCRI) in samples of solid He below 1-200 mK temperatures are conjectured to be describable in terms of a rarified Gross-Pitaevskii superfluid of vacancies (or, more generally, incommensuracies) with a transition temperature of about 50 mK, whose density is locally enhanced by crystal imperfections. We argue that the observations can be much affected by this density enhancement. We argue also that it is likely that the ground state of every pure Bose solid is supersolid.

cond-mat.stat-mech↗
arXiv2008

Simple Explanation of Fermi Arcs in Cuprate Pseudogaps: a Motional Narrowing Phenomenon

ARPES measurements on underdoped cuprates above the superconducting transition temperature exhibit the unique phenomenon of Fermi arcs, gapless arcs of Fermi surface around the nodal points of the superconducting gap, which terminate before reaching the antinodes. We show that this phenomenon is easily explained (including its temperature dependence and observed hole-electron asymmetry) as the natural consequence of a time-fluctuating d-wave gap.

cond-mat.supr-con↗
arXiv2008

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.

cond-mat.stat-mech↗
arXiv2007

Hidden Fermi Liquid: The Secret of High Tc Cuprates

I present a formalism for dealing directly with the effects of the Gutzwiller projection, which is implicit in the t-J model widely believed to underly the phenomenology of the high-Tc cuprates. I suggest that a true BCS condensation from a Fermi liquid state takes place, but in the unphysical space prior to projection. The theory which results upon projection does not follow conventional rules of diagram theory and in fact in the normal state is a Z=0 non-Fermi liquid. Anomalous properties of this strange metal normal state are predicted and compared to experiments.

cond-mat.str-el↗
arXiv2007

Bose Fluids Above Tc: Incompressible Vortex Fluids and "Supersolidity"

This paper emphasizes that non-linear rotational or diamagnetic susceptibility is characteristic of Bose fluids above their superfluid Tcs, and for sufficiently slow rotation or weak B-fields amounts to an incompressible response to vorticity. The cause is a missing term 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.

cond-mat.supr-con↗
arXiv2007

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.

cond-mat.supr-con↗
arXiv2006

Two New Vortex Liquids

It is suggested that the observations of nonlinear susceptibility and Nernst effect in cuprate superconductors above Tc, and those of non-classical rotational inertia in solid He, are two manifestations of a state of matter we call a vortex liquid, distinct from a conventional liquid in that its properties are dominated by conserved supercurrents flowing around a thermally fluctuating tangle of vortices.

cond-mat.stat-mech↗
arXiv2006

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.

cond-mat.supr-con↗
arXiv2006

The "Strange Metal" is a Projected Fermi Liquid with Edge Singularities

The puzzling "strange metal" phase of the high Tc cuprate phase diagram reveals itself as closer to a Fermi liquid than previously supposed: it is a consequence of Gutzwiller projection and does not necessarily require exotica such as an RVB or mysterious quantum critical points. There is a Fermi liquid-like excitation spectrum but the excitations are asymmetric between electrons and holes, show anomalous forward scattering and have Z equal to 0. We explain the power law dependence of conductivity on frequency and predict anomalies in the tunneling and photoemission spectra.

cond-mat.str-el↗