Platelike high-quality NaYbS2 rhombohedral single crystals with lateral dimensions of a few mm have been grown and investigated in great detail by bulk methods like magnetization and specific heat, but also by local probes like nuclear magnetic resonance (NMR), electron-spin resonance (ESR), muon-spin relaxation (µSR), and inelastic neutron scattering (INS) over a wide field and temperature range. Our single-crystal studies clearly evidence a strongly anisotropic quasi-2D magnetism and an emerging spin-orbit entangled S = 1/2 state of Yb towards low temperatures together with an absence of long-range magnetic order down to 260 mK. In particular, the clear and narrow Yb ESR lines together with narrow 23 Na NMR lines evidence an absence of inherent structural distortions in the system, which is in strong contrast to the related spin-liquid candidate YbMgGaO4 falling within the same space group R3m. This identifies NaYbS2 as a rather pure spin-1/2 triangular lattice magnet and a new putative quantum spin liquid.Introduction. -In low-dimensional quantum magnets, competing confined magnetic exchange interactions restrict the magnetic degrees of freedom, which leads to a strong frustration accompanied by enhanced quantum fluctuations. Ultimately this prevents the systems from longrange order, and the ground state is supposed to be a magnetic liquid. There are various types of such quantum spin liquids (QSL) depending on the lattice geometry (in 2D: square-, triangular-, kagome-, or honeycomb-type; in 3D: hyperkagome, hyperhoneycomb, or pyrochlore), the magnetic exchange (e.g. Heisenberg, Kitaev, or Dzyaloshinskii-Moriya type), and the magnetic ion itself [1][2][3][4]. Planar spin-1/2 triangular lattice magnets (TLMs) with antiferromagnetic exchange interactions are ideal QSL candidates as proposed by P. W. Anderson [5]. A few examples are found among the organic materials, such as K-(BEDT-TTF) 2 Cu 2 (CN) 3 [6] and EtnMe 4−n Sb[Pd(DMIT) 2 ] 2 [7], whereas among inorganic compounds such QSL model systems are very rare, e.g. Ba 3 CuSb 2 O 9 [8].
Superconducting [(Li1−xFex)OH](Fe1−yLiy)Se (x≈0.2, y≈0.08) was synthesized by hydrothermal methods and characterized by single‐crystal and powder X‐ray diffraction. The structure contains alternating layers of anti‐PbO type (Fe1−yLiy)Se and (Li1−xFex)OH. Electrical resistivity and magnetic susceptibility measurements reveal superconductivity at 43 K. An anomaly in the diamagnetic shielding indicates ferromagnetic ordering near 10 K while superconductivity is retained. The ferromagnetism is from the iron atoms in the (Li1−xFex)OH layer. Isothermal magnetization measurements confirm the superposition of ferromagnetic and superconducting hysteresis. The internal ferromagnetic field is larger than the lower, but smaller than the upper critical field of the superconductor. The formation of a spontaneous vortex phase where both orders coexist is supported by 57Fe‐Mössbauer spectra, 7Li‐NMR spectra, and μSR experiments.
or most of its history, the superconductivity of strontium ruthenate (Sr 2 RuO 4) (ref. 1) has been understood in terms of an odd-parity two-component order parameter with equal-spin pairing in the RuO 2 planes: p x ± ip y (refs. 2-5). This order parameter is chiral: the Cooper pairs have angular momentum l = ±1. The evidence for chirality comes from the zero-field muon spin relaxation (ZF-μSR) data 6 , observation of a non-zero Kerr rotation below the critical temperature T c (ref. 7) and signs in the junction experiments of domains in the superconducting state 8,9 , while evidence for equal-spin pairing came from the absence of a change in the Knight shift below T c in nuclear magnetic resonance 10 and polarized neutron scattering 11 measurements. The Knight shift is related to the spin susceptibility; in conventional opposite-spin-pairing superconductors, it is suppressed below T c. However, in new measurements, it has been found that the Knight shift is, in fact, suppressed below T c (refs. 12-14), by a magnitude that is unlikely to be reconcilable with equal-spin pairing. This revision has called into question a number of other results on Sr 2 RuO 4. It raises a particular challenge for experiments that indicate chirality, because opposite-spin pairing implies an even-parity momentum-space gap structure. If the order parameter is constrained to be even parity, chiral, and composed of components that are degenerate on the tetragonal lattice of Sr 2 RuO 4 , the only possibility is d xz ± id yz order 15. Under conventional understanding, this is a highly unlikely order parameter because it
Topological materials ranging from topological insulators to Weyl and Dirac semimetals form one of the most exciting current fields in condensed-matter research. Many half-Heusler compounds, RPtBi (R = rare earth), have been theoretically predicted to be topological semimetals. Among various topological attributes envisaged in RPtBi, topological surface states, chiral anomaly, and planar Hall effect have been observed experimentally. Here, we report an unusual intrinsic anomalous Hall effect (AHE) in the antiferromagnetic Heusler Weyl semimetal compounds GdPtBi and NdPtBi that is observed over a wide temperature range. In particular, GdPtBi exhibits an anomalous Hall conductivity of up to 60 Ω⋅cm and an anomalous Hall angle as large as 23%. Muon spin-resonance (μSR) studies of GdPtBi indicate a sharp antiferromagnetic transition () at 9 K without any noticeable magnetic correlations above Our studies indicate that Weyl points in these half-Heuslers are induced by a magnetic field via exchange splitting of the electronic bands at or near the Fermi energy, which is the source of the chiral anomaly and the AHE.
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