Elastoresistivity in the incommensurate charge density wave phase of BaNi₂(As₁₋ₓPₓ)₂

Electronic nematicity, the breaking of the crystal lattice rotational symmetry by the electronic fluid, is a fascinating quantum state of matter. In this work, using electronic transport under strain we investigate the electronic nematicity of BaNi$_2$(As$_{1−x}$P$_x$)$_2$, a candidate system for charge-induced nematicity. We report a large B$_{1g}$ elastoresistance coefficient that is maximized at the tetragonal-to-orthorhombic transition temperature, that slightly precedes the first-order triclinic transition. An hysteretic behavior is observed in the resistance versus strain sweeps and interpreted as the pinning of orthorhombic domains. Remarkably, the elastoresistance only onsets together with a strong enhancement of the incommensurate charge density wave of the material, strongly suggesting that this electronic instability is uniaxial in nature and drive the orthorhombic transition. The absence of sizeable elastoresistance above this electronic phase clearly contrasts dynamic and static electronic nematicity. Finally, the elastoresistance temperature dependence that strongly differs from the Curie-Weiss form of iron-based superconductors reveals major differences for the respective coupling of electronic nematicity to the lattice. Our results uncover an extremely strain-sensitive platform to study electronic anisotropy induced by a charge-density-wave instability

Using strain to uncover the interplay between two- and three-dimensional charge density waves in high-temperature superconducting YBa₂Cu₃O_y

Uniaxial pressure provides an efficient approach to control charge density waves in YBa2Cu3Oy. It can enhance the correlation volume of ubiquitous short-range two-dimensional charge-density-wave correlations, and induces a long-range three-dimensional charge density wave, otherwise only accessible at large magnetic fields. Here, we use x-ray diffraction to study the strain dependence of these charge density waves and uncover direct evidence for a form of competition between them. We show that this interplay is qualitatively described by including strain effects in a nonlinear sigma model of competing superconducting and charge-density-wave orders. Our analysis suggests that strain stabilizes the 3D charge density wave in the regions between disorder-pinned domains of 2D charge density waves, and that the two orders compete at the boundaries of these domains. No signatures of discommensurations nor of pair density waves are observed. From a broader perspective, our results underscore the potential of strain tuning as a powerful tool for probing competing orders in quantum materials

A new method to position and functionalize metal-organic framework crystals

With controlled nanometre-sized pores and surface areas of thousands of square metres per gram, metal-organic frameworks (MOFs) may have an integral role in future catalysis, filtration and sensing applications. In general, for MOF-based device fabrication, well-organized or patterned MOF growth is required, and thus conventional synthetic routes are not suitable. Moreover, to expand their applicability, the introduction of additional functionality into MOFs is desirable. Here, we explore the use of nanostructured poly-hydrate zinc phosphate (α-hopeite) microparticles as nucleation seeds for MOFs that simultaneously address all these issues. Affording spatial control of nucleation and significantly accelerating MOF growth, these α-hopeite microparticles are found to act as nucleation agents both in solution and on solid surfaces. In addition, the introduction of functional nanoparticles (metallic, semiconducting, polymeric) into these nucleating seeds translates directly to the fabrication of functional MOFs suitable for molecular size-selective applications

Crystallisation route map

A route map for the assessment of crystallisation processes is presented. A theoretical background on solubility, meta-stable zone width, nucleation and crystal growth kinetics is presented with practical examples. The concepts of crystallisation hydrodynamics and the application of population balances and computational fluid dynamics for modelling crystallisation processes and their scaling up are also covered

Light-induced electron emission from polymethylphenyl siloxane oils

Light-induced electron emission from tetramethyl tetraphenyl trisiloxane, (Dow-Corning silicone oil DC704) and trimethyl pentaphenyl siloxane (Wacker Chemie silicone oil AN175) has been measured as a function of photon energy. Absolute quantum yield and threshold energy were determined. The threshold energy of 7.5 eV for both siloxanes is comparable to the thresholds of other polymethylphenyl siloxanes with phenyl/methyl ratios of 1/3 and 1/18, which have been investigated by the authors. The quantum yield as a function of photon energy shows a systematic change with variation of the phenyl/methyl ratio. This dependence on the molecular structure is ascribed to a change of the initial ionization quantum yiel

Photoconductivity of an anthracene 2,2,4,4 tetramethylpentane solution pressure effect on the photoionization of solute and solvent

The photoconductivity spectrum of a solution of anthracene AN in 2,2,4,4 tetramethylpentane TMP was measured as a function of pressure up to 2 kbar. The threshold energies of photoionization of the solute AN and of the solvent TMP increase with pressure. The relative quantum yield for charge carrier generation decreased with increasing pressure. The concomitant reduction of the initial separation distance of the geminate charge carrier pairs may be due to an increase of the number of inelastic collisions caused by the increased density of the liquid within the sphere of Coulomb attraction of the positive io

Light induced electron emission from silicone oils

Light induced electron emission from silicone fluids has been measured as a function of photon energy. Emission energy thresholds were determined. Taking into account published data on the photoconductivity energy threshold in these fluids, values for the polarization energy of the positive ion and for the energy of the electronic conduction level could be deduced. In addition, some gas phase ionization potentials were determine