arXiv subjects

J. Betouras

Publications and source records attributed to J. Betouras.

3 recordsLinked to original sources

arXiv1999

Effects of carrier concentration on the superfluid density of high-T_c cuprates

The absolute values and temperature, T, dependence of the in-plane magnetic penetration depth, $λ_{ab}$, of La_{2-x}Sr_xCuO_4 and HgBa_2CuO_{4+δ} have been measured as a function of carrier concentration. We find that the superfluid density, $ρ_s$, changes substantially and systematically with doping. The values of $ρ_{s}(0)$ are closely linked to the available low energy spectral weight as determined by the electronic entropy just above T_c and the initial slope of $ρ_{s}(T)/ρ_{s}(0)$ increases rapidly with carrier concentration. The results are discussed in the context of a possible relationship between $ρ_s$ and the normal-state (or pseudo) energy gap.

cond-mat.supr-con↗

arXiv1995

Mixed symmetry superconductivity in two-dimensional Fermi liquids

We consider a 2D isotropic Fermi liquid with attraction in both $s$ and $d$ channels and examine the possibility of a superconducting state with mixed $s$ and $d$ symmetry of the gap function. We show that both in the weak coupling limit and at strong coupling, a mixed $s+id$ symmetry state is realized in a certain range of interaction. Phase transitions between the mixed and the pure symmetry states are second order. We also show that there is no stable mixed $s+d$ symmetry state at any coupling.

cond-mat↗

arXiv1995

Temperature dependent gap anisotropy in Bi$_{2}$Sr$_{2}$CaCu$_{2}$ O$_{8+x}$ as evidence for a mixed-symmetry ground state

In a recent experiment, Ma et al. measured the temperature dependence of the gap anisotropy of oxygen-annealed Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+x}$. Their measurements were taken along the two directions $Γ- M$ and $Γ- X$. They found that the gap along both directions is nonzero at low temperatures and that the ratio is strongly temperature dependent. We show, using Ginzburg-Landau theory, that this behavior can be obtained if one assumes the existence of s-wave and d-wave components for the order parameter. Our theory predicts orthorhombic anisotropy in the gap and anomalous behavior for the electronic specific heat below T$_c$.

cond-mat↗