Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userMultigap superconductivity in RbCa2Fe4As4F2 investigated using muSR measurements
136
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
The superconducting properties of the recently discovered double Fe$_2$As$_2$ layered high-$T_c$ superconductor RbCa$_2$Fe$_4$As$_4$F$_2$ with $T_capprox$ 30~K have been investigated using magnetization, heat capacity, transverse-field (TF) and zero-field (ZF) muon-spin rotation/relaxation ($mu$SR) measurements. Our low field magnetization measurements and heat capacity (C$_p$) reveal an onset of bulk superconductivity with $T_{bf c}sim$ 30.0(4) K. Furthermore, the heat capacity exhibits a jump at $T_{bf c}$ of $Delta$C$_p$/$T_{bf c}$=94.6 (mJ/mole-K$^2$) and no clear effect of applied magnetic fields was observed on C$_p$(T) up to 9 T between 2 K and 5 K. Our analysis of the TF-$mu$SR results shows that the temperature dependence of the magnetic penetration depth is better described by a two-gap model, either isotropic $s$+$s$-wave or $s$+$d$-wave than a single gap isotropic $s$-wave or $d$-wave model for the superconducting gap. The presence of two superconducting gaps in RbCa$_2$Fe$_4$As$_4$F$_2$ suggests a multiband nature of the superconductivity, which is consistent with the multigap superconductivity observed in other Fe-based superconductors, including ACa$_2$Fe$_4$As$_4$F$_2$ (A=K and Cs). Furthermore, from our TF-$mu$SR study we have estimated an in-plane penetration depth $lambda_{mathrm{ab}}$$(0)$ =231.5(3) nm, superconducting carrier density $n_s = 7.45 times 10^{26}~ $m$^{-3}$, and carriers effective-mass $m^*$ = 2.45textit{m}$_{e}$. Our ZF $mu$SR measurements do not reveal a clear sign of time reversal symmetry breaking at $T_{bf c}$, but the temperature dependent relaxation between 150 K and 1.2 K might indicate the presence of spin-fluctuations. The results of our present study have been compared with those reported for other Fe pnictide superconductors.
rate research
Read More
We have investigated the bulk and microscopic properties of the rhombohedral intermediate valence superconductor CeIr$_3$ by employing magnetization, heat capacity, and muon spin rotation and relaxation ($mu$SR) measurements. The magnetic susceptibility indicates bulk superconductivity below $T_mathrm{C} = 3.1$~K. Heat capacity data also reveal a bulk superconducting transition at $T_mathrm{C} = 3.1$~K with a second weak anomaly near 1.6~K. At $T_{mathrm{C}}$, the jump in heat capacity $Delta C$/$gamma T_{mathrm{C}} sim 1.39(1)$, is slightly less than the BCS weak coupling limit of 1.43. Transverse-field $mu$SR measurements suggest a fully gapped, isotropic, $s$-wave superconductivity with 2$Delta(0)/k_{mathrm{B}}T_{mathrm{C}} = 3.76(3)$, very close to 3.56, the BCS gap value for weak-coupling superconductors. From the temperature variation of magnetic penetration depth, we have also determined the London penetration depth $lambda_{mathrm{L}}(0) = 435(2)$~nm, the carriers effective mass enhancement $m^{*} = 1.69(1)m_{mathrm{e}}$ and the superconducting carrier density $n_{mathrm{s}} = 2.5(1)times 10^{26}$ carriers m$^{-3}$. The fact that LaIr$_3$, with no $4f$-electrons, and CeIr$_3$ with $4f^{n}$ electrons where $n le 1$-electron (Ce ion in a valence fluctuating state), both exhibit the same $s$-wave gap symmetry indicates that the physics of these two compounds is governed by the Ir-$d$ band near the Fermi-level, which is in agreement with previous band structure calculations.
We performed thermal conductivity measurements on a single crystal of the ferromagnetic superconductorUCoGe under magnetic field. Two different temperature dependencies of the thermal conductivity are observed, for H//b linear at low magnetic field and quadratic for magnetic field larger than 1 Tesla. At the same field value, a plateau appears in the field dependency of the residual term of thermal conductivity. Such observations suggest a multigap superconductivity with a line of nodes in the superconducting gap.
We have studied the quasiparticle excitation spectrum of the superconductor Ba8Si46 by local tunneling spectroscopy. Using high energy resolution achieved in Superconductor-Superconductor junctions we observed tunneling conductance spectra of a non-conventional shape revealing two distinct energy gaps, DeltaL = 1.3meV and DeltaS = 0.9meV. The analysis of tunneling data evidenced that DeltaL is the principal superconducting gap while DeltaS, smaller and more dispersive, is induced into an intrinsically non-superconducting band of the material by the inter-band quasiparticle scattering.
Recently, a new family of iron-based superconductors called 12442 was discovered and the muon spin relaxation ($mu$SR) measurements on KCa$_2$Fe$_4$As$_4$F$_2$ and CsCa$_2$Fe$_4$As$_4$F$_2$ polycrystals, two members of the family, indicated that both have a nodal superconducting gap structure with $s+d$ pairing symmetry. Here we report the ultralow-temperature thermal conductivity measurements on CsCa$_2$Fe$_4$As$_4$F$_2$ single crystals ($T_c$ = 29.3 K). A negligible residual linear term $kappa_0/T$ in zero field and the field dependence of $kappa_0/T$ suggest multiple nodeless superconducting gaps in CsCa$_2$Fe$_4$As$_4$F$_2$. This gap structure is similar to CaKFe$_4$As$_4$ and moderately doped Ba$_{1-x}$K$_x$Fe$_2$As$_2$, but contrasts to the nodal gap structure indicated by the $mu$SR measurements on CsCa$_2$Fe$_4$As$_4$F$_2$ polycrystals.
We investigate the temperature dependence of the lower critical field $H_{c1}(T)$, the field at which vortices penetrate into the sample, of a high-quality fluorine-doped NdFeAsO single crystal under static magnetic fields $H$ parallel to the $c$-axis. The temperature dependence of the first vortex penetration field has been experimentally obtained and pronounced changes of the $H_{c1}$(T) curvature are observed, which is attributed to the multiband superconductivity. Using a two-band model with $s$-wave-like gaps, the temperature-dependence of the lower critical field $H_{c1}(T)$ can be well described. These observations clearly show that the superconducting energy gap in fluorine-doped NdFeAsO is nodeless. The values of the penetration depth at $T$ = 0,K have been determined and confirm that the pnictide superconductors obey an Uemura-style relationship between $T_{c}$ and $lambda_{ab}(0)^{-2}$
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
