Related papers: Electron-phonon coupling induced pseudogap and the…

We investigate the electronic background as well as the O2-O3 mode at 330 cm^-1 of highly doped YbBa2Cu3O7-delta in B1g symmetry. Above the critical temperature Tc the spectra consist of an almost constant electronic background and…

Two possible phases of superhard material BC3 originating from the cubic diamond structure are investigated by ab initio pseudopotential density functional method using generalized gradient approximation (GGA). We calculate their elastic…

Several decades after the discovery of superconductivity in bismuthates, the strength of their electron-phonon coupling and its evolution with doping remain puzzling. To clarify these issues, polycrystalline hole-doped…

The quasiparticle relaxation dynamics of the iron-based superconductor CsCa$_2$Fe$_4$As$_4$F$_2$ ($T_c$ $\sim$ 29 K) were investigated using ultrafast optical spectroscopy. A pseudogap ($\Delta_{PG}$ $\approx$ 3.3 meV) was observed to open…

We study a single-particle density of states (DOS) in a model of Tomonaga-Luttinger liquid with small (large) values of the Luttinger parameter $K_\rc < 0.17$, ($K_\rc > 5.82$), in the charge sector. We explain that such values of $K_\rc$…

We use first-principles methods to study doped strong ferroelectrics (taking BaTiO$_3$ as a prototype). Here we find a strong coupling between itinerant electrons and soft polar phonons in doped BaTiO$_3$, contrary to Anderson/Blount's…

Magnetic measurements have been carried out in the superconducting and normal states of the optimally doped nonmagnetic bismuthate superconductor Ba0.63K0.37BiO3. The magnetic data along with previous muSR, resistivity, and tunneling data…

We have observed a softening of phonons and a structural phase transition in a superconducting Ba0.59K0.41BiO3 (Tc = 31 K) single crystal using elastic and inelastic neutron scattering measurements. The soft phonon occurs for the [111]…

The conductance curves of point-contact tunnel junctions between Ag and $\rm Ba_{1-x}K_xBiO_3$ ($x\simeq 0.4$) reveal a BCS behavior with low leakage current at zero voltage and some broadening of the superconducting-gap structure. In the…

We use ultrafast optical spectroscopy to study the nonequilibrium quasiparticle relaxation dynamics of the iron-based superconductor KCa$_2$Fe$_4$As$_4$F$_2$ with $T_c=33.5$ K. Our results reveal a possible pseudogap ($\Delta_{PG}$ = 2.4…

We have analysed optical reflectivity data for Ba_{1-x}K_xBiO_3 in the far-infrared region using Migdal-Eliashberg theory and found it inconsistent with standard electron-phonon coupling: Whereas the superconducting state data could be…

Many complex electronic systems exhibit so-called pseudogaps, which are poorly-understood suppression of low-energy spectral intensity in the absence of an obvious gap-inducing symmetry. Here we investigate the superconductor…

Pseudogap phase in superconductors continues to be an outstanding puzzle that differentiates unconventional superconductors from the conventional ones (BCS-superconductors). Employing high resolution photoemission spectroscopy on a highly…

Scanning tunneling spectroscopy has been used to reveal signatures of a bosonic mode in the local quasiparticle density of states of superconducting FeSe films. The mode appears below Tc as a 'dip-hump' feature at energy \Omega ~ 4.7 kBTc…

The discovery of superconductivity at 203K in SH$_3$ is an important step toward higher values of $T_c$. Predictions based on state-of-the-art DFT for the electronic structure, including one preceding experimental confirmation, showed the…

We investigate the physical properties of the Ba$_{1-x}$K$_x$BiO$_3$ compounds with a focus on the optical properties. Results from the simple Holstein model, describing a single band coupled to an oxygen breathing mode with parameters…

Electron-boson coupling plays a key role in superconductivity for many systems. However, in copper-based high-temperature ($T_c$) superconductors, its relation to superconductivity remains controversial despite strong spectroscopic…

The optical properties of the superconducting single crystal Rb$_{0.8}$Fe$_{1.68}$Se$_2$ with $T_{c}$ $\simeq$ 31 K have been measured over a wide frequency range in the $ab$ plane. We found that the optical conductivity is dominated by a…

By means of the first-principles density-functional theory calculation and Wannier interpolation, electron-phonon coupling and superconductivity are systematically explored for boron-doped LiBC (i.e. LiB$_{1+x}$C$_{1-x}$), with $x$ between…

Bulk n-type SrTiO3 (STO) has long been known to possess a superconducting ground state at an exceptionally dilute carrier density. This has raised questions about the applicability of the BCS-Eliashberg paradigm with its underlying…