Related papers: Kohn Anomalies in Superconductors
The absorption of light by a metal disturbs the electron distribution around the Fermi surface. Here, we calculate the phonon dispersion relations of free-electron-like metal, bcc sodium, with a stepwise electron distribution function by…
We argue that recently measured downward dispersion of the neutron resonance peak in cuprate superconductors is naturally explained if the resonance is viewed as a spin-1 collective mode in a d-wave superconductor. The reduction of the…
The phenomenon of the so called Fermion condensation, a phase transition analogous to Bose condensation but for Fermions, postulated in the past to occur in systems with strong momentum dependent forces, is reanalysed in a model with…
We have used angular resolved photoemission to measure the angular dependence of the superconducting gap in highly overdoped Bi2212 (Tc=65K). While the node at 45 degrees is conserved, we find substantial deviation from a first order d-wave…
A simple interlayer pair tunneling is solved exactly. We find that in the normal state spin-1/2 particle and hole excitations are gapped. But the state is an unusual metal, characterized by novel fermionic spin zero and charge +2e and -2e…
The effect of helical Dirac states on surface phonons in a topological insulators is investigated. Their coupling is derived in the continuum limit by assuming displacement dependent Dirac cones. The resulting renormalisation of sound…
Kohn anomalies are kinks or dips in phonon dispersions which are pronounced in low-dimensional materials. We investigate the effects of non-adiabatic phonon self-energy on Kohn anomalies in one-dimensional metals by developing a model that…
The normal state behaviour of the density of states of the electrons described by the BOSON - FERMION model for Bose-Einstein condensation driven superconductivity is characterized by the appearence of a pseudogap which developes into a…
In multi-band metals quasi-particles arising from different atomic orbitals coexist at a common Fermi surface. Superconductivity in these materials may appear due to interactions within a band (intra-band) or among the distinct metallic…
We present scanning tunnelling spectroscopy measurements on the heavy fermion superconductor PrOs$_4$Sb$_{12}$. Our results show that the superconducting gap opens over a large part of the Fermi surface. The deviations from isotropic BCS…
We report high-resolution photoemission spectroscopy of newly-discovered iron-based layered superconductor La(O$_{0.93}$F$_{0.07}$)FeAs (Tc = 24 K). We found that the superconducting gap shows a marked deviation from the isotropic s-wave…
For more than a decade, the unusual distribution of electrons observed in ARPES (angle-resolved photoemission spectroscopy) data within the energy range of ~30meV to ~300meV below the Fermi level, known as the ARPES range, has remained a…
Conventional superconductivity follows Bardeen-Cooper-Schrieffer(BCS) theory of electrons-pairing in momentum-space, while superfluidity is the Bose-Einstein condensation(BEC) of atoms paired in real-space. These properties of solid metals…
In several iron-arsenide superconductors there is strong evidence for a fully gapped superconducting state consistent with either a conventional s-wave symmetry or an unusual $s_\pm$ state where there the gap changes sign between the…
Inelastic light scattering studies on single crystal of electron-doped Ca(Fe0.95Co0.05)2As2 superconductor, covering the tetragonal to orthorhombic structural transition as well as magnetic transition at TSM ~ 140 K and superconducting…
Two-dimensional system of the fermions with the indirect Einstein phonon-exchange attraction and added local four-fermion interaction is considered. It is shown that in such a system at resulting attraction between particles a new…
A reduction of the density of states near the Fermi energy in the normal state (pseudogap) of high-temperature oxide superconductors is examined on the basis of the two-dimensional tight-binding model with effective interactions due to…
Phonon coherence elucidates the propagation and interaction of phonon quantum states within superlattice, unveiling the wave-like nature and collective behaviors of phonons. Taking MoSe$_2$/WSe$_2$ lateral heterostructures as a model…
A recent experimental study announced the emergence of superconductivity in La$_3$Ni$_2$O$_7$ under pressure, with the highest observed superconducting transition temperature ($T_c$) reaching approximately 80 K beyond 14 GPa. While…
Recent spectroscopic measurements in a number of strongly correlated metals that exhibit non-Fermi liquid like properties have observed evidence of anomalous frequency and momentum-dependent charge-density fluctuations. Specifically, in the…