Chirality Induced Tilted-Hill Giant Nernst Signal

We reveal a novel source of giant Nernst response exhibiting strong non-linear temperature and magnetic field dependence including the mysterious tilted-hill temperature profile observed in a pleiad of materials. The phenomenon results directly from the formation of a chiral ground state, e.g. a chiral d-density wave, which is compatible with the eventual observation of diamagnetism and is distinctly different from the usual quasiparticle and vortex Nernst mechanisms. Our picture provides a unified understanding of the anomalous thermoelectricity observed in materials as diverse as hole doped cuprates and heavy-fermion compounds like URu2Si2.Comment: 5 pages and 4 figures, Final version accepted by Phys. Rev. Let

Comment on ``Quasiparticle Decay Effects in the Superconducting Density of States: Evidence for d-Wave Pairing in the Cuprates''

We comment on a letter publised in PRL by: D. Coffey and L. Coffey, Phys. Rev. Lett. {\bf 70}, 1529 (1993) where it is claimed that the dip structure above the gap is evidence for d-wave pairing. We show that the analysis in this letter is completely contradictory to all ARPES experiments (including those which are considered to be evidence for d-wave), since this letter predicts a dip structure in the direction in which the gap is absent (within the d-wave scenario) and the absence of the dip in the direction in which the gap is maximal. We point out a series of additional experimental facts that exclude the analysis of the previous letter and that can be naturally understool within a strong coupling s-wave analysis made by the author of this comment [Phys. Rev. B {\bf 51} (Rapid. Comm.), 1381 (1995)].Comment: 5 pages, latex, Comment submitted to Phys. Rev. Let

Holographic Charge Density Waves

We discuss a gravity dual of a charge density wave consisting of a U(1) gauge field and two scalar fields in the background of an AdS$_4$ Schwarzschild black hole together with an antisymmetric field (probe limit). Interactions drive the system to a phase transition below a critical temperature. We numerically compute the ground states characterized by modulated solutions for the gauge potential corresponding to a dynamically generated unidirectional charge density wave in the conformal field theory. Signatures of the holographic density waves are retrieved by studying the dynamical response to an external electric field. We find that this novel holographic state shares many common features with the standard condensed matter version of charge density wave systems.Comment: 5 pages, 2 figures; improved discussion, published versio

Universal Spin-Flip Transition in Itinerant Antiferromagnets

We report a universal spin flip (SF) transition as a function of temperature in spin-density-wave (SDW) systems. At low temperatures the antiferromagnetic (AFM) polarization is parallel to the applied field and above a critical temperature the AFM polarization {\it flips} perpendicular to the field. This transition occurs in {\it any} SDW system and may be considered as a qualitative probe of the itinerant character of AFM in a given material. Our SF transition resolves the longstanding puzzle of the SF transition observed in cromium and may be at the origin of the equally puzzling SDW-I to SDW-II transition in Bechgaard salts for which we make experimental predictions

Majorana Zero Modes in Ferromagnetic Wires without Spin-Orbit Coupling

We present a novel controllable platform for engineering Majorana zero modes. The platform consists of a ferromagnetic metallic wire placed among conventional superconductors, which are in proximity to ferromagnetic insulators. We demonstrate that Majorana zero modes emerge localised at the edges of the ferromagnetic wire, due to the interplay of the applied supercurrents and the induced by proximity exchange fields with conventional superconductivity. Our mechanism does not rely on the pairing of helical fermions by combining conventional superconductivity with spin-orbit coupling, but rather exploits the misalignment between the magnetization of the ferromagnetic insulators and that of the ferromagnetic wire