Observation of possible nonlinear anomalous Hall effect in organic two-dimensional Dirac fermion system.

We report the observation of nonlinear anomalous Hall effect (NLAHE) in the multilayered organic conductor α-(BEDT-TTF)Iin the charge order (CO) insulating phase just under the critical pressure for transition into two-dimensional (2D) massless Dirac fermion (DF) phase. We successfully extracted the finite nonlinear Hall voltage proportional to square current at zero magnetic field. The observed NLAHE features, current direction dependence and correlation with CO, are consistent with the previous estimation assuming 2D massive DF with a pair of tilted Dirac cones.

Triangular-Lattice Organic Mott Insulator with a Disorder-Free Polyanion.

We report the synthesis, crystal and band structures, and transport properties of organic conductor κ-(ET)Cu[Au(CN)]Cl [ET = bis(ethylenedithio)tetrathiafulvalene], which has a triangular spin-lattice ( = /) composed of (ET) dimers and polyanions with no disorder. The anisotropy of triangular lattice '/ = 1.19 and physical properties indicate that this material is the first ET-based quantum-spin-liquid candidate having a nearly regular triangular lattice with a disorder-free anion.

NMR Spectroscopy Unchained: Attaining the Highest Signal Enhancements in Dissolution Dynamic Nuclear Polarization.

Dynamic nuclear polarization (DNP) via the dissolution method is one of the most successful methods for alleviating the inherently low Boltzmann-dictated sensitivity in nuclear magnetic resonance (NMR) spectroscopy. This emerging technology has already begun to positively impact chemical and metabolic research by providing the much-needed enhancement of the liquid-state NMR signals of insensitive nuclei such as C by several thousand-fold. In this Perspective, we present our viewpoints regarding the key elements needed to maximize the NMR signal enhancements in dissolution DNP, from the very core of the DNP process at cryogenic temperatures, DNP instrumental conditions, and chemical tuning in sample preparation to current developments in minimizing hyperpolarization losses during the dissolution transfer process.

Dynamic nuclear polarization of carbonyl and methyl C spins of acetate using 4-oxo-TEMPO free radical.

Hyperpolarization of C-enriched biomolecules via dissolution dynamic nuclear polarization (DNP) has enabled real-time metabolic imaging of a variety of diseases with superb specificity and sensitivity. The source of the unprecedented liquid-state nuclear magnetic resonance spectroscopic or imaging signal enhancements of >10 000-fold is the microwave-driven DNP process that occurs at a relatively high magnetic field and cryogenic temperature. Herein, we have methodically investigated the relative efficiencies of C DNP of single or double C-labeled sodium acetate with or without H-enrichment of the methyl group and using a 4-oxo-TEMPO free radical as the polarizing agent at 3.

Magnetic-Field-Dependent Lifetimes of Hyperpolarized C Spins at Cryogenic Temperature.

Using a home-built cryogen-free dynamic nuclear polarization (DNP) system with a variable magnetic field capability, C spin-lattice T relaxation times of hyperpolarized [1-C] carboxylates (sodium acetate, glycine, sodium pyruvate, and pyruvic acid) doped with trityl OX063 free radical were systematically measured for the first time at different field strengths up to 9 T at T = 1.8 K. Our data reveal that the C T values of these frozen hyperpolarized C samples vary drastically with the applied magnetic field B according to an apparent empirical power-law dependence (C T ∝ B, 2.