Pressure-induced melting of magnetic order and emergence of new quantum state in alpha-RuCl3

Here we report the observation of pressure-induced melting of antiferromagnetic (AFM) order and emergence of a new quantum state in the honeycomb-lattice halide alpha-RuCl3, a candidate compound in the proximity of quantum spin liquid state. Our high-pressure heat capacity measurements demonstrate that the AFM order smoothly melts away at a critical pressure (Pc) of 0.7 GPa. Intriguingly, the AFM transition temperature displays an increase upon applying pressure below the Pc, in stark contrast to usual phase diagrams, for example in pressurized parent compounds of unconventional superconductors. Furthermore, in the high-pressure phase an unusual steady of magnetoresistance is observed. These observations suggest that the high-pressure phase is in an exotic gapped quantum state which is robust against pressure up to ~140 GPa.Comment: 20 pages, 4 figure

Coexistence of superconductivity with exotic ferromagnetic state in pressurized non-superconducting UTe2_2

The discovery of superconductivity in heavy Fermion UTe$_2$, a candidate topological and triplet-paired superconductor, has aroused widespread interest. However, to date, superconductivity has only been reported in nonstoichiometric crystals of UTe$_2$ with a Te deficit. Here, we demonstrate that the application of uniaxial pressure induces superconductivity in stoichiometric UTe$_2$ crystals. Measurements of resistivity, magnetoresistance and susceptibility reveal that uniaxial pressure results in a suppression of the Kondo coherent state seen at ambient pressure, leading to the emergence of superconductivity initially at 1.5 GP, followed by the development of bulk superconductivity at 4.8 GPa. The superconducting state coexists with an exotic ferromagnetically ordered (FM) state that develops just below the onset temperature of the superconducting transition. High-pressure synchrotron x-ray diffraction measurements performed at 20 K indicate that no structural phase transition occurs over the measured pressure range. Our results not only demonstrate the coexistence of superconductivity with an exotic ferromagnetic state in pressurized stoichiometric UTe$_2$, but also highlight a vital role of Te deficiency in developing superconductivity at ambient pressures.Comment: 17 pages, 4 figure

A solution-processable and ultra-permeable conjugated microporous thermoset for selective hydrogen separation.

The synthesis of a polymer that combines the processability of plastics with the extreme rigidity of cross-linked organic networks is highly attractive for molecular sieving applications. However, cross-linked networks are typically insoluble or infusible, preventing them from being processed as plastics. Here, we report a solution-processable conjugated microporous thermoset with permanent pores of ~0.4 nm, prepared by a simple heating process. When employed as a two-dimensional molecular sieving membrane for hydrogen separation, the membrane exhibits ultrahigh permeability with good selectivity for H2 over CO2, O2, N2, CH4, C3H6 and C3H8. The combined processability, structural rigidity and easy feasibility make this polymeric membrane promising for large-scale hydrogen separations of commercial and environmental relevance

Breakdown of Three-dimensional Dirac Semimetal State in pressurized Cd3As2

We report the first observation of a pressure-induced breakdown of the 3D-DSM state in Cd3As2, evidenced by a series of in-situ high-pressure synchrotron X-ray diffraction (XRD) and single crystal transport measurements. We find that Cd3As2 undergoes a structural phase transition from a metallic tetragonal (T) phase in space group I41/acd to a semiconducting monoclinic (M) phase in space group P21/c at critical pressure 2.57 GPa, above this pressure, an activation energy gap appears, accompanied by distinct switches in Hall resistivity slope and electron mobility. These changes of crystal symmetry and corresponding transport properties manifest the breakdown of the 3D-DSM state in pressurized Cd3As2.Comment: 17 pages, 4 figure