Superconductivity in the noncentrosymetric Li2Pd(3-x)AgxB with x=0.0, 0.1 and 0.3

TL;DR

This study investigates how partial Ag substitution affects superconductivity in Li2Pd3B, revealing that the system exhibits weak spin-triplet pairing and strong-coupling BCS behavior with an isotropic energy gap.

Contribution

It provides new experimental data on the effects of Ag doping on the superconducting properties of Li2Pd3B, including critical fields, specific heat, and pairing symmetry.

Findings

Ag substitution slightly lowers critical fields.

Superconductivity shows strong-coupling BCS characteristics.

Energy gap is isotropic and consistent with weak spin-triplet pairing.

Abstract

We studied the partial substitution of Ag in the noncentrosymetric superconducting compounds Li$_2$Pd$_{3-x}$Ag$_x$B with x=0.0, 0.1 and 0.3. Magnetization, resistivity and specific heat measurements were performed in this system. From electrical measurements we obtained the critical temperature $T_c$. The upper critical field at zero temperature was determined with Werthamer-Helfand equation, $\mu_0H^{WHH}_{c2}(0)$, and $\mu_0H^{linear}_{c2}(0)$ and the coherence length, $\xi(0)$. The Value of $\mu_0H^{linear}_{c2}(0)$ and $\mu_0H^{WHH}_{c2}(0)$ is lower than the calculated paramagnetic Pauli limit suggesting that the spin-triplet pairing is weak in the system. From specific heat measurements we obtained the parameters of the normal state; the Sommerfeld coefficient, $\gamma$, the electronic density of states at the Fermi level, $N(E_F)$ and the Debye temperature, $\theta_D$. In the superconducting state the obtained values were; $\Delta C/\gamma T_c$, the electron phonon coupling, $\lambda_{e-ph}$, the superconducting energy gap, $2\Delta_0$, and the ratio $2\Delta_0 /k_BT_c$. The electronic specific heat is well described by the BCS theory, suggesting that the energy gap is isotropic and in a strong coupling state.