اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدالتعتيم الاعتمادي للسوبر كوندكتيوتي لـ (Ca1-xNax)Fe2As2
The doping dependence of superconductivity of (Ca1-xNax)Fe2As2
649
0
0.0
(
0
)
اسأل ChatGPT حول البحث
وقد تم تحضير وتشخيص الكرومات المنفردة CaFe2As2 والبوليكريستالات (Ca1-xNax)Fe2As2 (0 < x < 0.66) باستخدام القياسات الهندسية والمغناطيسية والنقل الكهربائي والحرارة. تظهر هذه القياسات أن تحول الهندسي / المغناطيسي في CaFe2As2 في 165 درجة كلوري تم تخفيضه بشكل متزايد بالتحميل الناتي وأن السوبر كوندوكتيبيليتي يمكن أن يتحقق في منطقة التحميل الواسعة. ل 0.3 < x < 0.36، تشير الحساسيات المغناطيسية إلى إمكانية توازن الجهد الكتلي الذري (SDW) والسوبر كوندوكتيبيليتي. وتم التعرف على المرحلة السوبر كوندوكتيبيلية المتعلقة بمستوى التحميل الناتي في (Ca1-xNax)Fe2As2 للحجم المعتاد x = 0.36، 0.4، 0.5، 0.6 و 0.66، بحيث تشمل Tc = 17 درجة كلوري، 19 درجة كلوري، 22 درجة كلوري، 33 درجة كلوري، و 33 درجة كلوري على التوالي. وتم دراسة تأثير المجال المغناطيسي على تحولات السوبر كوندوكتيبيليتي للعينات التي تحمل الحجم x = 0.66 مع حدود المجال الكبيرة العليا Hc2 تقريبا 103 تولز، وبالتالي تم عرض مخطط للجهد الكتلي الذري والسوبر كوندوكتيبيليتي باعتماد مستوى التحميل.
Single crystalline CaFe2As2 and (Ca1-xNax)Fe2As2 polycrystals (0 < x < 0.66) are synthesized and characterized using structural, magnetic, electronic transport, and heat capacity measurements. These measurements show that the structural/magnetic phase transition in CaFe2As2 at 165 K is monotonically suppressed by the Na doping and that superconductivity can be realized over a wide doping region. For 0.3 < x < 0.36, the magnetic susceptibilities indicate the possible coexistence of the spin density wave (SDW) and superconductivity. Superconducting phases corresponding to the Na doping level in (Ca1-xNax)Fe2As2 for nominal x = 0.36, 0.4, 0.5, 0.6, and 0.66, with Tc = 17 K, 19 K, 22 K, 33 K, and 33 K, respectively, are identified. The effects of the magnetic field on the superconductivity transitions for x = 0.66 samples with high upper critical fields Hc2 approx 103 T are studied, and a phase diagram of the SDW and superconductivity as a function of the doping level is thus presented.
قيم البحث
اقرأ أيضاً
The solid solution of antimonide-oxides Ba1-xKxTi2Sb2O (0 < x < 1) has been synthesized by solid-state reactions and characterized by X-ray powder diffraction (CeCr2Si2C-type structure; P4/mmm, Z = 1). The crystal structure consists of Ti2Sb2O-layers
that are stacked with layers of barium atoms along the c-axis. BaTi2Sb2O is a known superconductor with a critical temperature (Tc) of 1.2 K. Substitution of barium through potassium raises Tc up to 6.1 K at 12 % potassium, while no superconductivity emerges with concentrations higher than 20 %. Anomalies in electrical transport and magnetic susceptibility indicate charge density wave (CDW) instabilities. The CDW transition temperatures (Ta) decrease from 50 K in the parent compound to 28 K at 10 % potassium substitution. No CDW transition was detected at higher concentrations, and no evidence for a reduction of the lattice symmetry below Ta was found. The lattice parameters vary linearly while the unit cell volume increases with higher potassium concentrations. The phase diagrams Tc(x) and Ta(x) of Ba1-xKxTi2Sb2O are remarkably similar to the known series Ba1-xNaxTi2Sb2O (0 < x < 0.33) in spite of the reverse volume effect. From this we conclude that the charge and not the volume determines the phase diagrams of these superconducting antimony oxides.
We report the interplay between charge-density-wave (CDW) and superconductivity of 1$T$-Fe$_{x}$Ta$_{1-x}$S$_{2}$ ($0leq x leq 0.05$) single crystals. The CDW order is gradually suppressed by Fe-doping, accompanied by the disappearance of pseudogap/M
ott-gap as shown by the density functional theory (DFT) calculations. The superconducting state develops at low temperatures within the CDW state for the samples with the moderate doping levels. The superconductivity strongly depends on $x$ within a narrow range, and the maximum superconducting transition temperature is 2.8 K as $x=0.02$. We propose that the induced superconductivity and CDW phases are separated in real space. For high doping level ($x>0.04$), the Anderson localization (AL) state appears, resulting in a large increase of resistivity. We present a complete electronic phase diagram of 1$T$-Fe$_{x}$Ta$_{1-x}$S$_{2}$ system that shows a dome-like $T_{c}(x)$.
We report the discovery and characterization of a novel 112-type iron pnictide EuFeAs2, with La-doping induced superconductivity in a series of Eu1-xLaxFeAs2. The polycrystalline samples were synthesized through solid state reaction method only withi
n a very narrow temperature window around 1073 K. Small single crystals were also grown from a flux method with the size about 100 um. The crystal structure was identified by single crystal X-ray diffraction analysis as a monoclinic structure with space group of P21/m. From resistivity and magnetic susceptibility measurements, we found that the parent compound EuFeAs2 shows a Fe2+ related antiferromagnetic/structural phase transition near 110 K and a Eu2+ related antiferromagnetic phase transition near 40 K. La doping suppressed the both phase transitions and induced superconducting transition with a Tc ~ 11 K for Eu0.85La0.15FeAs2.
To explore the origin of the unusual non-bulk superconductivity with a Tc up to 49 K reported in the rare-earth-doped CaFe2As2 , the chemical composition, magnetization, specific heat, resistivity, and annealing effect are systematically investigated
on nominal (Ca1-xRx)Fe2As2 single crystals with different xs and R = La, Ce, Pr, and Nd. All display a doping-independent Tc once superconductivity is induced, a doping-dependent low field superconducting volume fraction f, and a large magnetic anisotropy {eta} in the superconducting state, suggesting a rather inhomogeneous superconducting state in an otherwise microscale-homogenous superconductor. The wavelength dispersive spectroscopy and specific heat show the presence of defects which are closely related to f, regardless of the R involved. The magnetism further reveals that the defects are mainly superparamagnetic clusters for R = Ce, Pr, and Nd with strong intercluster interactions, implying that defects are locally self-organized. Annealing at 500 {deg}C, without varying the doping level x, suppresses f profoundly but not the Tc. The above observations provide evidence for the crucial role of defects in the occurrence of the unusually high Tc ~ 49 K in (Ca1-xRx)Fe2As2 and are consistent with the interface-enhanced superconductivity recently proposed.
In high-superconducting transition temperature ($T_{rm c}$) iron-based superconductors, interband sign reversal ($s_{rm pm}$) and sign preserving ($s_{rm ++}$) $s$-wave superconducting states have been primarily discussed as the plausible superconduc
ting mechanism. We study Co impurity scattering effects on the superconductivity in order to achieve an important clue on the pairing mechanism using single crystal Fe$_{1-x}$Co$_x$Se and depict a phase diagram of a FeSe system. Both superconductivity and structural transition / orbital order are suppressed by the Co replacement on the Fe sites and disappear above $x$ = 0.036. These correlated suppressions represent a common background physics behind these physical phenomena in the multiband Fermi surfaces of FeSe. By comparing experimental data and theories so far proposed, the suppression of $T_{rm c}$ against the residual resistivity is shown to be much weaker than that predicted in the case of a general sign reversal and a full gap $s_{pm}$ models. The origin of the superconducting paring in FeSe is discussed in terms of its multiband electronic structure.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
