اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدFully gapped superconductivity in centrosymmetric and non-centrosymmetric Re-B compounds probed with $mu$SR
129
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
We present a comprehensive study on superconducting properties of Re$_7$B$_3$ and Re$_3$B through specific heat, magnetic susceptibility, resistivity, and transverse and zero-field muon spin rotation/relaxation ($mu$SR) experiments on polycrystalline samples. Re$_7$B$_3$ (T$_C$ = 3.2~K) is a non-centrosymmetric type-II ($kappa$ $approx$ 9.27) superconductor in the weak coupling ($lambda_{e-ph}$ = 0.54) regime. On the other hand, Re$_3$B (T$_C$ = 5.19~K) is a centrosymmetric type-II ($kappa$ $approx$ 34.55) superconductor in the moderate coupling ($lambda_{e-ph}$ = 0.64) regime. Our transverse-field $mu$SR measurements show evidence for isotropically gapped BCS type superconductivity with normalized gap ($Delta_0/k_BT_C$) values of 1.69 (Re$_7$B$_3$) and 1.75 (Re$_3$B).
قيم البحث
اقرأ أيضاً
We report the discovery of superconductivity in pressurized CeRhGe3, until now the only remaining non-superconducting member of the isostructural family of non-centrosymmetric heavy-fermion compounds CeTX3 (T = Co, Rh, Ir and X = Si, Ge). Superconduc
tivity appears in CeRhGe3 at a pressure of 19.6 GPa and the transition temperature Tc reaches a maximum value of 1.3 K at 21.5 GPa. This finding provides an opportunity to establish systematic correlations between superconductivity and materials properties within this family. Though ambient-pressure unit-cell volumes and critical pressures for superconductivity vary substantially across the series, all family members reach a maximum Tcmax at a common critical cell volume Vcrit, and Tcmax at Vcrit increases with increasing spin-orbit coupling strength of the d-electrons. These correlations show that substantial Kondo hybridization and spin-orbit coupling favor superconductivity in this family, the latter reflecting the role of broken centro-symmetry.
In the recently discovered antiperovskite phosphide (Ca,Sr)Pd$_3$P, centrosymmetric (CS) and non-centrosymmetric (NCS) superconducting phases appear depending on the Sr concentration, and their transition temperatures ($T_mathrm{c}$) differ by as muc
h as one order of magnitude. In this study, we investigated the superconducting properties and electronic band structures of CS orthorhombic (CSo) (Ca$_{0.6}$Sr$_{0.4}$)Pd$_3$P ($T_mathrm{c}$ = 3.5 K) and NCS tetragonal (NCSt) (Ca$_{0.25}$Sr$_{0.75}$)Pd$_3$P ($T_mathrm{c}$ = 0.32 K) samples with a focus on explaining their large $T_mathrm{c}$ difference. Specific heat measurements indicated that CSo (Ca$_{0.6}$Sr$_{0.4}$)Pd$_3$P was an s-wave superconductor in a moderate-coupling regime with a 2$Delta$$_0$/k$_B$$T_mathrm{c}$ value of 4.0. Low-lying phonons leading to the strong coupling in the structurally analogous SrPt$_3$P were unlikely to be present in CSo (Ca$_{0.6}$Sr$_{0.4}$)Pd$_3$P. Given that CSo (Ca$_{0.6}$Sr$_{0.4}$)Pd$_3$P and NCSt (Ca$_{0.25}$Sr$_{0.75}$)Pd$_3$P exhibited similar Debye temperatures ($Theta$$_D$) of approximately 200 K, the large $T_mathrm{c}$ difference could not be attributed to $Theta$$_D$.$T_mathrm{c}$ of each phase was accurately reproduced based on the Bardeen-Cooper-Schrieffer (BCS) theory using experimental data and the density of states of the Fermi level $N$(0) calculated from their band structures. We concluded that the considerable suppression of $T_mathrm{c}$ in NCSt (Ca$_{0.25}$Sr$_{0.75}$)Pd$_3$P can be primarily attributed to the decrease in $N$(0) associated with the structural phase transition without considering the lack of inversion symmetry.
We report measurements of the temperature dependence of the magnetic penetration depth lambda(T) in non-centrosymmetric superconductor Re_3W. We employed two experimental techniques: extraction of lambda(T) from magnetic {em dc}-susceptibility, measu
red on a powder sample, and the rf tunnel diode resonator technique, where a bulk polycrystalline sample was used. The results of both techniques agree: the temperature dependence of the penetration depth can be well described by weak-coupling, dirty-limit, s-wave BCS theory where we obtain $Delta(0)/k_BT_C=1.76$. No evidence for unconventional pairing resulting from the absence of the inversion symmetry is found.
Superconductivity and magnetism in the non-centrosymmetric heavy fermion compound CePt$_3$Si and related materials are theoretically investigated. Based on the randam phase approximation (RPA) analysis for the extended Hubbard model we describe the h
elical spin fluctuation induced by the Rashba-type anti-symmetric spin-orbit coupling and identify the two stable superconducting phases with either dominantly p-wave ($s$ + $P$-wave) or d-wave ($p$ + $D$ + $f$-wave) symmetry. The influcnce of the coexistent anti-ferromagnetic order is investigated in both states. The SC order parameter, quasiparticle density of state, NMR $1/T_{1}T$, specific heat, anisotropy of $H_{rm c2}$ and possible multiple phase transitions are discussed in details. The comparison with experimental results indicates that the $s$ + $P$-wave superconducting state is likely realized in CePt$_3$Si.
Electrical resistivity, specific heat and NMR measurements classify non-centrosymmetric $rm Mo_3Al_2C$ ($beta$-Mn type, space group $P4_132$) as a strong-coupled superconductor with $T_c = 9$~K deviating notably from BCS-like behaviour. The absence o
f a Hebbel-Slichter peak, a power law behaviour of the spin-lattice relaxation rate (from $^{27}$Al NMR), a $T^3$ temperature dependence of the specific heat and a pressure enhanced $T_c$ suggest unconventional superconductivity with a nodal structure of the superconducting gap. Relativistic DFT calculations reveal a splitting of degenerate electronic bands due to the asymmetric spin-orbit coupling, favouring a mix of spin-singlet and spin triplet components in the superconducting condensate, in absence of strong correlations among electrons.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
