Related papers: Collective $d-$wave Excitonic Modes in the Fe-Supe…
FeSe is employed as reference material to elucidate the observed high Tc superconducting behaviour of the related layered iron pnictides. The structural and ensuing semimetallic band structural forms are here rather unusual, with the…
The magnetic excitations in the superconducting electron-doped cuprates are studied in the framework of spin-density-wave description. The superconducting resonance is a natural product of the superconductivity due to the opening of d-wave…
Recently we have proposed a s+g-wave model for the superconductivity in borocarbides, YNi2B2C and LuNi2B2C. In the present paper we first summarize thermodynamic properties of s+g-wave model. Then we shall analyse the recent Raman spectra…
In 1966 Leggett used a two-band superconductor to show that a new collective mode could exist at low temperatures, corresponding to a counter-flow of the superconducting condensates in each band. Here, the theory of electronic Raman…
Spin-fluctuation-mediated superconductivity is conventionally associated with d_{x^2-y^2} pairing. We show that a generalized model of antiferromagnetic spin fluctuations in three dimensions may also yield a state with formal ``s-wave''…
We point out that unidirectional bond-centered charge-density-wave states in cuprates involve electronic order in both s- and d-wave channels, with non-local Coulomb repulsion suppressing the s-wave component. The resulting…
Two-dimensional semiconductors host excitons with very large oscillator strengths and binding energies due to significantly reduced carrier screening. Two-dimensional semiconductors integrated with optical cavities are emerging as a…
A periodic layer of resonant scatterers is considered in the dipolar approximation. An asymptotic expression for the field diffracted is given in terms of an impedance operator. It is shown that surface Bloch modes appear as a collective…
Using a renormalization group approach, we determine the phase diagram of an extended quasi-one-dimensional electron gas model that includes interchain hopping, nesting deviations and both intrachain and interchain repulsive interactions.…
The issue of probing the pseudogap regime of the cuprate superconductors, specifically with regard to the existence and nature of superconducting pairing correlations of d-wave symmetry, is explored theoretically. It is shown that if the…
Fluctuations near second-order quantum phase transitions in d-wave superconductors can cause strong damping of fermionic excitations, as observed in photoemission experiments. The damping of the gapless nodal quasiparticles can arise…
In this work we investigate the role of exciton resonances in coherent anti-Stokes Raman scattering (er-CARS) in single walled carbon nanotubes (SWCNTs). We drive the nanotube system in simultaneous phonon and excitonic resonances, where we…
The enigmatic cuprate superconductors have attracted resurgent interest with several recent reports and discussions of competing orders in the underdoped side. Motivated by this, here we address the natural question of fragility of the…
We theoretically investigate coherent optical excitations of collective modes in two-band BCS superconductors, which accommodate two Higgs modes and one Leggett mode corresponding, respectively, to the amplitude and relative-phase…
We calculate the infrared conductivity of a stack of coupled, two-dimensional superconducting planes within the Fermi liquid theory of superconductivity. We include the effects of random scattering processes and show that the presence of…
We consider the resonant scattering of coherent electromagnetic waves by a Raman-like process in the gamma ray range off electrostatic modes in a quantum plasma using a collective Klein-Gordon-Maxwell model. The growth rates for the most…
Recent Raman scattering data in B_{1g} and B_{2g} geometries in the superconducting state of underdoped cuprates were interpreted as evidence for two distinct energy gaps. We argue that these data can be equally well explained within a one…
The nature of the pairing state in iron-based superconductors is the subject of much debate. Here we argue that in one material, the stoichiometric iron pnictide KFe2As2, there is overwhelming evidence for a d-wave pairing state,…
We study superconductor-ferromagnet bi-layers, not only for s-wave but also for d-wave superconductors. We observe oscillations of the critical temperature when varying the thickness of the ferromagnetic layer for both s-wave and d-wave…
The observation of an unusual spin resonant excitation in the superconducting state of various High-Tc ~copper oxides by inelastic neutron scattering measurements is reviewed. This magnetic mode % (that does not exist in conventional…