Correcting 100 years of misunderstanding: electric fields in superconductors, hole superconductivity, and the Meissner effect

From the outset of superconductivity research it was assumed that no electrostatic fields could exist inside superconductors, and this assumption was incorporated into conventional London electrodynamics. Yet the London brothers themselves initially (in 1935) had proposed an electrodynamic theory of superconductors that allowed for static electric fields in their interior, which they unfortunately discarded a year later. I argue that the Meissner effect in superconductors necessitates the existence of an electrostatic field in their interior, originating in the expulsion of negative charge from the interior to the surface when a metal becomes superconducting. The theory of hole superconductivity predicts this physics, and associated with it a macroscopic spin current in the ground state of superconductors ("Spin Meissner effect"), qualitatively different from what is predicted by conventional BCS-London theory. A new London-like electrodynamic description of superconductors is proposed to describe this physics. Within this theory superconductivity is driven by lowering of quantum kinetic energy, the fact that the Coulomb repulsion strongly depends on the character of the charge carriers, namely whether electron- or hole-like, and the spin-orbit interaction. The electron-phonon interaction does not play a significant role, yet the existence of an isotope effect in many superconductors is easily understood. In the strong coupling regime the theory appears to favor local charge inhomogeneity. The theory is proposed to apply to all superconducting materials, from the elements to the high $T_c$ cuprates and pnictides, is highly falsifiable, and explains a wide variety of experimental observations.Comment: Proceedings of the conference "Quantum phenomena in complex matter 2011 - Stripes 2011", Rome, 10 July -16 July 2011, to be published in J. Supercond. Nov. Mag

Superconductivity from Undressing. II. Single Particle Green's Function and Photoemission in Cuprates

Experimental evidence indicates that the superconducting transition in high $T_c$ cuprates is an 'undressing' transition. Microscopic mechanisms giving rise to this physics were discussed in the first paper of this series. Here we discuss the calculation of the single particle Green's function and spectral function for Hamiltonians describing undressing transitions in the normal and superconducting states. A single parameter, $\Upsilon$, describes the strength of the undressing process and drives the transition to superconductivity. In the normal state, the spectral function evolves from predominantly incoherent to partly coherent as the hole concentration increases. In the superconducting state, the 'normal' Green's function acquires a contribution from the anomalous Green's function when $\Upsilon$ is non-zero; the resulting contribution to the spectral function is $positive$ for hole extraction and $negative$ for hole injection. It is proposed that these results explain the observation of sharp quasiparticle states in the superconducting state of cuprates along the $(\pi,0)$ direction and their absence along the $(\pi,\pi)$ direction.Comment: figures have been condensed in fewer pages for easier readin

Determining R-parity violating parameters from neutrino and LHC data

In supersymmetric models neutrino data can be explained by R-parity violating operators which violate lepton number by one unit. The so called bilinear model can account for the observed neutrino data and predicts at the same time several decay properties of the lightest supersymmetric particle. In this paper we discuss the expected precision to determine these parameters by combining neutrino and LHC data and discuss the most important observables. We show that one can expect a rather accurate determination of the underlying R-parity parameters assuming mSUGRA relations between the R-parity conserving ones and discuss briefly also the general MSSM as well as the expected accuracies in case of a prospective e+ e- linear collider. An important observation is that several parameters can only be determined up to relative signs or more generally relative phases.Comment: 13 pages, 13 figure

Superconductivity from Undressing

Photoemission experiments in high $T_c$ cuprates indicate that quasiparticles are heavily 'dressed' in the normal state, particularly in the low doping regime. Furthermore these experiments show that a gradual undressing occurs both in the normal state as the system is doped and the carrier concentration increases, as well as at fixed carrier concentration as the temperature is lowered and the system becomes superconducting. A similar picture can be inferred from optical experiments. It is argued that these experiments can be simply understood with the single assumption that the quasiparticle dressing is a function of the local carrier concentration. Microscopic Hamiltonians describing this physics are discussed. The undressing process manifests itself in both the one-particle and two-particle Green's functions, hence leads to observable consequences in photoemission and optical experiments respectively. An essential consequence of this phenomenology is that the microscopic Hamiltonians describing it break electron-hole symmetry: these Hamiltonians predict that superconductivity will only occur for carriers with hole-like character, as proposed in the theory of hole superconductivity

Clinical potential of necitumumab in non-small cell lung carcinoma

Despite significant progress, new therapeutic approaches for advanced non-small cell lung cancer (NSCLC) are highly needed, particularly for the treatment of patients with squamous cell carcinoma. The epidermal growth factor receptor (EGFR) is often overexpressed in NSCLC and represents a relevant target for specific treatments. Although EGFR mutations are more frequent in non-squamous histology, the receptor itself is more often overexpressed in squamous NSCLC. Necitumumab is a human monoclonal antibody that is able to inhibit the EGFR pathway and cause antibody-dependent cell cytotoxicity. This drug has been studied in combination with first-line chemotherapy for advanced NSCLC in two Phase III trials, and a significant survival benefit was reported in squamous NSCLC (SQUIRE trial); by contrast, necitumumab did not prove itself beneficial in non-squamous histotype (INSPIRE trial). On the basis of the SQUIRE results, necitumumab was approved in combination with cisplatin and gemcitabine as a first-line treatment for advanced squamous NSCLC, both in the US and Europe, where its availability is limited to patients with EGFRexpressing tumors. The aim of this review is to describe the tolerability and the efficacy of necitumumab by searching the available published data and define its potential role in the current landscape of NSCLC treatment

R-parity Conserving Supersymmetry, Neutrino Mass and Neutrinoless Double Beta Decay

We consider contributions of R-parity conserving softly broken supersymmetry (SUSY) to neutrinoless double beta (\znbb) decay via the (B-L)-violating sneutrino mass term. The latter is a generic ingredient of any weak-scale SUSY model with a Majorana neutrino mass. The new R-parity conserving SUSY contributions to \znbb are realized at the level of box diagrams. We derive the effective Lagrangian describing the SUSY-box mechanism of \znbb-decay and the corresponding nuclear matrix elements. The 1-loop sneutrino contribution to the Majorana neutrino mass is also derived. Given the data on the \znbb-decay half-life of $^{76}$Ge and the neutrino mass we obtain constraints on the (B-L)-violating sneutrino mass. These constraints leave room for accelerator searches for certain manifestations of the 2nd and 3rd generation (B-L)-violating sneutrino mass term, but are most probably too tight for first generation (B-L)-violating sneutrino masses to be searched for directly.Comment: LATEX, 29 pages + 4 (uuencoded) figures appende