Three-dimensional (3D) Dirac semimetals exist close to topological phase boundaries which, in principle, should make it possible to drive them into exotic new phases, such as topological ...superconductivity, by breaking certain symmetries. A practical realization of this idea has, however, hitherto been lacking. Here we show that the mesoscopic point contacts between pure silver (Ag) and the 3D Dirac semimetal Cd3As2 (ref. ) exhibit unconventional superconductivity with a critical temperature (onset) greater than 6 K whereas neither Cd3As2 nor Ag are superconductors. A gap amplitude of 6.5 meV is measured spectroscopically in this phase that varies weakly with temperature and survives up to a remarkably high temperature of 13 K, indicating the presence of a robust normal-state pseudogap. The observations indicate the emergence of a new unconventional superconducting phase that exists in a quantum mechanically confined region under a point contact between a Dirac semimetal and a normal metal.
Black, air‐stable crystals of the new ruthenate(V) Sr3(Ag2/3Sr1/6)RuO6 were grown in a silver ampoule using KO2 as oxidative flux. X‐ray diffraction on single‐crystals revealed a rhombohedral ...structure with the space group R
3‾
${\bar{3}}$
c. Sr3(Ag2/3Sr1/6)RuO6 crystallizes isostructural to Sr4PtO6 in the K4CdCl6 structure type. By sharing trigonal faces, alternating RuO6 octahedra and (Ag2/3Sr1/6□1/6)O6 trigonal prisms form segmented chains running parallel to the crystallographic c‐axis. Eightfold coordinated strontium cations are located between the rods. Regardless of the wide spatial separation of the magnetic cations (588 and 594 pm), Sr3(Ag2/3Sr1/6)RuO6 shows long‐range antiferromagnetic order below the relatively high Néel temperature of 79 K in magnetic fields up to at least 9 T, as measurements of the magnetic susceptibility and heat capacity show. Despite the pseudo one‐dimensional character of the structure, the characteristic of the susceptibility indicates a three‐dimensional coupling of magnetic ions.
Despite a wide spatial separation of the magnetic cations, the oxide Sr3(Ag2/3Sr1/6)RuO6 shows robust antiferromagnetic order below the relatively high Néel temperature of 79 Kelvin in magnetic fields up to at least 9 Tesla. The new oxido‐ruthenate(V) was synthesized in a reactive potassium superoxide flux at high temperature.
Topological Weyl semimetals have recently attracted considerable attention among materials scientists as their properties are predicted to be protected against perturbations such as lattice ...distortion and chemical substitution. However, any experimental proof of such robustness is still lacking. In this study, we experimentally demonstrate that the topological properties of the ferromagnetic kagomé compound Co3Sn2S2 are preserved upon Ni substitution. We systematically vary the Ni content in Co3Sn2S2 single crystals and study their magnetic and anomalous transport properties. For the intermediate Ni substitution, we observe a remarkable increase in the coercive field while still maintaining significant anomalous Hall conductivity. The large anomalous Hall conductivity of these compounds is intrinsic, consistent with first-principles calculations, which proves its topological origin. Our results can guide further studies on the chemical tuning of topological materials for better understanding.
The design of new complex mixed metal tellurides (containing low toxicity cations) with intrinsic ultralow thermal conductivity is of paramount importance in the field of thermoelectrics. Herein, we ...report the synthesis and characterization of polycrystalline and single crystals of a new mixed-metal quaternary telluride Mn1.8(1)In0.8(1)Si2Te6. The structural aspects and chemical formula of this phase at room temperature have been established using single crystal X-ray diffraction and EDX studies. The trigonal centrosymmetric (space group: P31m) structure of the title phase has cell constants of a = b = 7.0483(7) Å and c = 7.1277(8) Å. The structure has three independent cationic sites, one mixed (In1/Mn1), one partially filled Mn2, and one Si1, which are bonded with Te1 atoms. Each metal atom (In and Mn) in the structure is octahedrally coordinated with six neighboring Te1 atoms. The structure also features dimers of Si atoms, and each Si atom is bonded to three Te1 atoms to form ethane-like Si2Te6 units. The optical absorption study of a polycrystalline Mn1.8In0.8Si2Te6 sample shows a narrow optical bandgap of 0.6(2) eV. Temperature-dependent resistivity and Seebeck coefficient studies confirmed the p-type semiconducting nature of the sample with high values of S (301 μV K−1 to 444 μV K−1). The total thermal conductivity (ktot) study of the polycrystalline sample shows a decreasing trend on heating with an extremely low value of 0.28 W m−1 K−1 at 773 K. Magnetic measurements indicate a glassy magnetic behavior for the sample below 8 K.
The B‐site ordered double perovskite Sr2CaOsO6 has been synthesized by a solid‐state reaction under ambient pressure. Sr2CaOsO6 is isostructural to Sr2NaOsO6 and Sr2CaReO6, thus crystallizes in the ...monoclinic space group P21/n, in contrast to cubic lattice symmetry reported in an earlier publication. The compound remains paramagnetic down to a temperature of 2 K. This finding is of relevance with regard to the high‐temperature ferromagnetism observed in Sr3OsO6 thin films and may find interest in view of possible exotic ground states in frustrated magnetic systems. Dedicated to Professor Antoine Maignan on the occasion of his 60th birthday.
Structure and Magnetic Properties of Sr2NaOsO6 Thakur, Gohil S.; Felser, Claudia; Jansen, Martin
European journal of inorganic chemistry,
November 15, 2020, Volume:
2020, Issue:
42
Journal Article
Peer reviewed
Open access
Sr2NaOsO6, an ordered double perovskite, was obtained by solid‐state synthesis. The compound crystallizes in a monoclinic cell P21/n, a = 5.7043(1) Å, b = 5.7828(1) Å, c = 8.0816(2) Å; β = 90.01(2)° ...and develops long‐range antiferromagnetic order at ≈ 17 K with strong canting generating a tiny spontaneous moment of 0.06 µB/Os ion. A fit of the high temperature susceptibility data according to a modified Curie–Weiss law revealed a small effective paramagnetic moment of 0.7 µB/Os, which underlines the substantial effect of spin‐orbit coupling in 5d oxides. A broad instead of a sharp lambda anomaly in specific heat data suggests frustration and strong magnetic disorder at the osmium lattice.
A new B‐site ordered, monoclinic double perovskite Sr2NaOsO6 is reported. It exhibits a long range antiferromagnet order below TN = 18 K but with strong spin canting. Magnetic and calorimetric studies suggest a considerable disorder at the magnetic lattice.
The design of new complex mixed metal tellurides (containing low toxicity cations) with intrinsic ultralow thermal conductivity is of paramount importance in the field of thermoelectrics. Herein, we ...report the synthesis and characterization of polycrystalline and single crystals of a new mixed-metal quaternary telluride Mn
In
Si
Te
. The structural aspects and chemical formula of this phase at room temperature have been established using single crystal X-ray diffraction and EDX studies. The trigonal centrosymmetric (space group:
3̄1
) structure of the title phase has cell constants of
=
= 7.0483(7) Å and
= 7.1277(8) Å. The structure has three independent cationic sites, one mixed (In1/Mn1), one partially filled Mn2, and one Si1, which are bonded with Te1 atoms. Each metal atom (In and Mn) in the structure is octahedrally coordinated with six neighboring Te1 atoms. The structure also features dimers of Si atoms, and each Si atom is bonded to three Te1 atoms to form ethane-like Si
Te
units. The optical absorption study of a polycrystalline Mn
In
Si
Te
sample shows a narrow optical bandgap of 0.6(2) eV. Temperature-dependent resistivity and Seebeck coefficient studies confirmed the
-type semiconducting nature of the sample with high values of
(301 μV K
to 444 μV K
). The total thermal conductivity (
) study of the polycrystalline sample shows a decreasing trend on heating with an extremely low value of 0.28 W m
K
at 773 K. Magnetic measurements indicate a glassy magnetic behavior for the sample below 8 K.
The manipulation of topological states in quantum matter is an essential pursuit of fundamental physics and next-generation quantum technology. Here we report the magnetic manipulation of Weyl ...fermions in the kagome spin-orbit semimetal Co_{3}Sn_{2}S_{2}, observed by high-resolution photoemission spectroscopy. We demonstrate the exchange collapse of spin-orbit-gapped ferromagnetic Weyl loops into paramagnetic Dirac loops under suppression of the magnetic order. We further observe that topological Fermi arcs disappear in the paramagnetic phase, suggesting the annihilation of exchange-split Weyl points. Our findings indicate that magnetic exchange collapse naturally drives Weyl fermion annihilation, opening new opportunities for engineering topology under correlated order parameters.
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Single crystals of a new twinned hexagonal perovskite compound Sr8Os6.3O24 have been synthesized, and structural and magnetic properties have been determined. The compound crystallizes in a hexagonal ...cell with lattice parameters a = 9.6988(3) Å and c = 18.1657(5) Å. The structure is an eight-layered hexagonal B-site deficient perovskite with the layer sequence (ccch)2 and represents the first example of a hexagonal structure among 5d oxides adopting a twin option. The sample shows spontaneous ferromagnetic magnetization below 430 K with a small saturation moment of 0.11 μB/Os ion. This is the highest Curie temperature (T C) reported for any bulk perovskite containing only 5d ions at the B site.
Polycrystalline Ba4NbIr3O12 has recently been shown to be a promising spin liquid candidate. We report an easy and reliable method to grow millimeter-sized single crystals of this trimer-based spin ...liquid candidate material with the actual stoichiometry of Ba4Nb0.8Ir3.2O12. The growth of large crystals is achieved using BaCl2 as flux. The crystals show a hexagonal plate-like habit with edges up to 3 mm in length. The structure is confirmed by single-crystal X-ray diffraction and is found to be the same as that of the previously reported phase Ba12Nb2.4Ir9.6O36 Ba4Nb0.8Ir3.2O12, indeed with a mixed occupancy of Nb/Ir at the 3a site. The magnetic and calorimetric study on the individual single crystals confirms the possibility of a spin liquid state consistent with a recent report on a polycrystalline sample.
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