41 research outputs found
Penetration depth and gap structure in the antiperovskite oxide superconductor SrSnO revealed by SR
We report a SR study on the antiperovskite oxide superconductor
SrSnO. With transverse-field SR, we observed the increase of the
muon relaxation rate upon cooling below the superconducting transition
temperature K, evidencing bulk superconductivity. The
exponential temperature dependence of the relaxation rate at low
temperatures suggests a fully gapped superconducting state. We evaluated the
zero-temperature penetration depth to be
around 320-1020 nm. Such a large value is consistent with the picture of a
doped Dirac semimetal. Moreover, we revealed that the ratio
is larger than those of ordinary
superconductors and is comparable to those of unconventional superconductors.
The relatively high for small carrier density may hint at an
unconventional pairing mechanism beyond the ordinary phonon-mediated pairing.
In addition, zero-field SR did not provide evidence of broken
time-reversal symmetry in the superconducting state. These features are
consistent with the theoretically proposed topological superconducting state in
SrSnO, as well as with -wave superconductivity.Comment: 9 pages, 9 figures, to be published in Physical Review
Spin-triplet superconductivity in Weyl nodal-line semimetals
Topological semimetals are three dimensional materials with symmetry-protected massless bulk excitations. As a special case, Weyl nodal-line semimetals are realized in materials either having no inversion or broken time-reversal symmetry and feature bulk nodal lines. The 111-family of materials, LaNiSi, LaPtSi and LaPtGe (all lacking inversion symmetry), belong to this class. Here, by combining muon-spin rotation and relaxation with thermodynamic measurements, we find that these materials exhibit a fully-gapped superconducting ground state, while spontaneously breaking time-reversal symmetry at the superconducting transition. Since time-reversal symmetry is essential for protecting the normal-state topology, its breaking upon entering the superconducting state should remarkably result in a topological phase transition. By developing a minimal model for the normal-state band structure and assuming a purely spin-triplet pairing, we show that the superconducting properties across the family can be described accurately. Our results demonstrate that the 111-family reported here provides an ideal test-bed for investigating the rich interplay between the exotic properties of Weyl nodal-line fermions and unconventional superconductivity
Growth of bulk single-crystal MnP helimagnet and its structural and NMR characterization
Bulk single crystals of manganese phosphide (MnP) were grown from melt at 1
GPa and 1200 C by using a cubic-anvil, high-pressure, and high-temperature
technique. The obtained black colored crystals exhibit a plate-like morphology,
with flat surfaces and maximum dimensions up to 4 x 2 x 0.5 mm3. The
orthorhombic crystal structure was confirmed by X-ray diffraction [Pnma, 62, Z
= 4, a = 5.2510(4) {\AA}, b = 3.1670(3) {\AA}, c = 5.90098 (4) {\AA} and V =
98.279(14) {\AA}3]. Temperature-dependent magnetization measurements reveal the
occurrence of two successive transitions: a paramagnetic to ferromagnetic
transition at Tc = 290.5 K and the development of a double helimagnetic order
at Ts = 44.5 K. Zero-field 31P NMR measurements in the FM and in the screw-spin
AFM state show prominent features, which are compared with previous
experimental data and theoretical calculations. The relatively large crystals
obtained here open up new possibilities for further explorations of this
interesting material.Comment: 4 tables, 7 figure
Application-driven quantum and statistical physics: a short course for future scientists and engineers, volume 2: equilibrium
Time-Reversal Symmetry Breaking in Re-Based Superconductors: Recent Developments
In the recent search for unconventional- and topological superconductivity, noncentrosymmetric superconductors (NCSCs) rank among the most promising candidate materials. Surprisingly, some of them—especially those containing rhenium—seem to exhibit also time-reversal symmetry (TRS) breaking in their superconducting state, while TRS is preserved in many other isostructural NCSCs. To date, a satisfactory explanation for such discrepant behavior, albeit crucial for understanding the unconventional superconductivity of these materials, is still missing. Here we review the most recent developments regarding the Re-based class, where the muon-spin relaxation (μSR) technique plays a key role due to its high sensitivity to the weak internal fields associated with the TRS breaking phenomenon. We discuss different cases of Re-containing superconductors, comprising both centrosymmetric- and noncentrosymmetric crystal structures, ranging from pure rhenium, to ReT (T = 3d-5d early transition metals), to the dilute-Re case of ReBe22. μSR results suggest that the rhenium presence and its amount are two key factors for the appearance and the extent of TRS breaking in Re-based superconductors. Besides summarizing the existing findings, we also put forward future research ideas regarding the exciting field of materials showing TRS breaking.ISSN:2296-424
Simultaneous Nodal Superconductivity and Time-Reversal Symmetry Breaking in the Noncentrosymmetric Superconductor CaPtAs
ISSN:0031-9007ISSN:1079-711
Probing the superconducting pairing of the La₄Be₃₃Pt₁₆ alloy via muon-spin spectroscopy
ISSN:0953-8984ISSN:1361-648