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Register a new userSuperconductivity Induced by Breaking Te2 Dimers of AuTe2
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Mineral calaverite AuTe2 is a layered compound with an incommensurately modulated structure. The modulation is characterized by the formation of molecular-like Te2 dimers. We have found that the breaking of Te2 dimers that occurs in Au1-xPtxTe2 results in the emergence of superconductivity at Tc = 4.0 K.
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The pressure dependences of resistivity and ac susceptibility have been measured in the mineral calaverite AuTe$_2$. Resistivity clearly shows a first-order phase transition into a high-pressure phase, consistent with the results of a previous structural analysis. We found zero resistivity and a diamagnetic shielding signal at low temperatures in the high-pressure phase, which clearly indicates the appearance of superconductivity. Our experimental results suggest that bulk superconductivity appears only in the high-pressure phase. For AuTe$_2$, the highest superconducting transition temperature under pressure is $T_{rm c}$ = 2.3 K at 2.34 GPa; it was $T_{rm c}$ = 4.0 K for Pt-doped (Au$_{0.65}$Pt$_{0.35}$)Te$_2$. The difference in $T_{rm c}$ between the two systems is discussed on the basis of the results obtained using the band calculations and McMillans formula.
We present an in-depth classification of the topological phases and Majorana fermion (MF) excitations that arise from the bulk interplay between unconventional multiband spin-singlet superconductivity and various magnetic textures. We focus on magnetic texture crystals with a periodically-repeating primitive cell of the helix, whirl, and skyrmion types. Our analysis is relevant for a wide range of layered materials and hybrid devices, and accounts for both strong and weak, as well as crystalline topological phases. We identify a multitude of accessible topological phases which harbor flat, uni- or bi-directional, (quasi-)helical, or chiral MF edge modes. This rich variety of MFs originates from the interplay between topological phases with gapped and nodal bulk energy spectra, with the resulting types of spectra and MFs controlled by the size of the pairing and magnetic gaps.
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Superconductivity is successfully induced by utilizing a battery-like reaction found in a typical Li-ion battery. Excess Fe in FeTe0.8S0.2 is electrochemically de-intercalated by applying a voltage in a citric acid solution. The superconducting properties improve with an increase in the applied voltage up to 1.5 V. This result suggests that an electrochemical reaction can be used as a novel method to develop new superconducting materials.
From detailed angle-resolved NMR and Meissner measurements on a ferromagnetic (FM) superconductor UCoGe (T_Curie ~ 2.5 K and T_SC ~ 0.6 K), we show that superconductivity in UCoGe is tightly coupled with longitudinal FM spin fluctuations along the c axis. We found that magnetic fields along the c axis (H || c) strongly suppress the FM fluctuations and that the superconductivity is observed in the limited magnetic field region where the longitudinal FM spin fluctuations are active. These results combined with model calculations strongly suggest that the longitudinal FM spin fluctuations tuned by H || c induce the unique spin-triplet superconductivity in UCoGe. This is the first clear example that FM fluctuations are intimately related with superconductivity.
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