اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدEvidence for Scattering-Dependent Multigap Superconductivity in Ba8Si46
437
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
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.
قيم البحث
اقرأ أيضاً
The recently discovered kagome superconductor CsV$_3$Sb$_5$ ($T_c simeq 2.5$ K) has been found to host charge order as well as a non-trivial band topology, encompassing multiple Dirac points and probable surface states. Such a complex and phenomenolo
gically rich system is, therefore, an ideal playground for observing unusual electronic phases. Here, we report on microscopic studies of its anisotropic superconducting properties by means of transverse-field muon spin rotation ($mu$SR) experiments. The temperature dependences of the in-plane and out-of-plane components of the magnetic penetration depth $lambda_{ab}^{-2}(T)$ and $lambda_{c}^{-2}(T)$ indicate that the superconducting order parameter exhibits a two-gap ($s+s$)-wave symmetry, reflecting the multiple Fermi surfaces of CsV3Sb5. The multiband nature of its superconductivity is further validated by the different temperature dependences of the anisotropic magnetic penetration depth $gamma_lambda(T)$ and upper critical field $gamma_{rm B_{c2}}(T)$, both in close analogy with the well known two-gap superconductor MgB$_2$. Remarkably, the high value of the $T_c/lambda^{-2}(0)$ ratio in both field orientations strongly suggests the unconventional nature of superconductivity. The relaxation rates obtained from zero field $mu$SR experiments do not show noticeable change across the superconducting transition, indicating that superconductivity does not break time reversal symmetry.
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.
We report a detailed study of specific heat, electrical resistivity and thermal expansion in combination with inelastic neutron and inelastic X-ray scattering to investigate the origin of superconductivity in the two silicon clathrate superconductors
Ba8Si46 and Ba24Si100. Both compounds have a similar structure based on encaged barium atoms in oversized silicon cages. However, the transition temperatures are rather different: 8 K and 1.5 K respectively. By extracting the superconducting properties, phonon density of states, electron-phonon coupling function and phonon anharmonicity from these measurements we discuss the important factors governing Tc and explain the difference between the two compounds.
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 $c$-axi
s. 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 $lambda_{ab}(0)^{-2}$
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
