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Abstract Superconducting performance is tunable not only via chemical modification or defect engineering, but also through external parameters such as pressure, though this method remains less readily accessible. In this work, we study how compression influences vortex dynamics and critical currents in an iron-based superconductor. Specifically, we perform magnetization measurements using an off-the-shelf pressure cell to investigate the effects of hydrostatic pressures up to 1.08 GPa on the magnetic properties of BaFe ${}_2$ (As ${}_{0.62}$ P ${}_{0.38}$ ) ${}_2$ crystals across a range of temperatures $T$ and magnetic fields $H$ . Although these pressures minimally affect the superconducting critical temperature, they produce a clear increase in the critical current density $J_{\mathrm{c}}(T,H)$ , a pronounced reduction in the rate of thermally activated vortex motion $S(T,H)$ , and can change the dominant vortex pinning mechanism. Furthermore, the effects of pressure are irreversible: after pressurization and subsequent release at room temperature, high-density microcracks are observed and the crystals retain their enhanced critical current densities. The second magnetization peak vanishes above 18 K after the pressure cycle, which we attribute to a transition from predominantly $\delta \kappa$ pinning to a mixed mechanism of $\delta T_{\mathrm{c}}$ and surface pinning. Lastly, a threefold increase in $J_{\mathrm{c}}$ , a more than 40% reduction in $S$ at 8 K and 0.5 T, and an expanded elastic-creep region were achieved after $1-2$ pressure cycles. These findings demonstrate the potential utility of pressure cycling for improving $J_{\mathrm{c}}$ , which may offer a simpler alternative compared to approaches such as chemical doping or the introduction of artificial pinning centers. 

A diverse range of stagnant flow patterns can be categorized as atmospheric blocking, and these flow patterns have distinct patterns of diabatic heating due to latent heat release. Climate model simulation and projection of atmospheric blocking remain a challenge, in part due to a lack of understanding of blocking diversity and the distinct roles of diabatic heating patterns. Here, we delineate observed blocking diversity using a local wave activity diagnostic and focus on two key archetypes: ridge and dipole blocks. Each type shows a distinctive flow pattern and associated diabatic heating. For ridge blocks, diabatic heating enhances the upstream wave activity, thus contributing to the persistence of blocks. In contrast, for dipole blocks, diabatic heating reduces the wave activity at the center of blocks, thus exerting a damping effect. The distinct roles of diabatic heating along with their preferred geographic locations provide insights in assessing blocking diversity in a warming climate. 

Abstract Cardiac organoids have emerged as powerful platforms for modeling human heart development and disease. However, traditional 2D microelectrode arrays (MEAs) are limited to planar recordings and fail to capture the 3D propagation of electrical signals. Here, programmable, shape‐adaptive, organoid‐encapsulating shell MEAs are presented as a technology that enables comprehensive 3D electrophysiological mapping. These on‐chip‐fabricated devices feature customizable geometries and electrode layouts tailored to an organoid's unique morphology. Shell MEAs generate high‐resolution 3D isochrone and conduction velocity maps, unveiling long‐term spatiotemporal field potential dynamics in spontaneously beating organoids. Furthermore, they integrate multiple modalities, such as calcium imaging to corroborate electrophysiological findings and pharmacological screening to assess organoid responses to isoproterenol, E‐4031, and serotonin. This platform represents a significant advance in bioelectronic interfaces, enabling high‐content 3D spatiotemporal functional analysis for cardiac disease modeling and pharmacological testing. 

Ever since the discovery of the charge density wave (CDW) transition in the kagome metal ${\mathrm{CsV}}_3{\mathrm{Sb}}_5$ , the nature of its symmetry breaking has been under intense debate. While evidence suggests that the rotational symmetry is already broken at the CDW transition temperature ( $T_{\mathrm{CDW}}$ ), an additional electronic nematic instability well below $T_{\mathrm{CDW}}$ has been reported based on the diverging elastoresistivity coefficient in the anisotropic channel ( $m_{E_{2g}}$ ). Verifying the existence of a nematic transition below $T_{\mathrm{CDW}}$ is not only critical for establishing the correct description of the CDW order parameter, but also important for understanding low-temperature superconductivity. Here, we report elastoresistivity measurements of ${\mathrm{CsV}}_3{\mathrm{Sb}}_5$ using three different techniques probing both isotropic and anisotropic symmetry channels. Contrary to previous reports, we find the anisotropic elastoresistivity coefficient $m_{E_{2g}}$ is temperature independent, except for a step jump at $T_{\mathrm{CDW}}$ . The absence of nematic fluctuations is further substantiated by measurements of the elastocaloric effect, which show no enhancement associated with nematic susceptibility. On the other hand, the symmetric elastoresistivity coefficient $m_{A_{1g}}$ increases below $T_{\mathrm{CDW}}$ , reaching a peak value of 90 at $T^{*}=20\mathrm{K}$ . Our results strongly indicate that the phase transition at $T^{*}$ is not nematic in nature and the previously reported diverging elastoresistivity is due to the contamination from the $A_{1g}$ channel. Published by the American Physical Society2024 

Uniaxial strain has been widely used as a powerful tool for investigating and controlling the properties of quantum materials. However, existing strain techniques have so far mostly been limited to use with bulk crystals. Although recent progress has been made in extending the application of strain to two-dimensional van der Waals (vdW) heterostructures, these techniques have been limited to optical characterization and extremely simple electrical device geometries. Here, we report a piezoelectric-based in situ uniaxial strain technique enabling simultaneous electrical transport and optical spectroscopy characterization of dual-gated vdW heterostructure devices. Critically, our technique remains compatible with vdW heterostructure devices of arbitrary complexity fabricated on conventional silicon/silicon dioxide wafer substrates. We demonstrate a large and continuously tunable strain of up to −0.15% at millikelvin temperatures, with larger strain values also likely achievable. We quantify the strain transmission from the silicon wafer to the vdW heterostructure, and further demonstrate the ability of strain to modify the electronic properties of twisted bilayer graphene. Our technique provides a highly versatile new method for exploring the effect of uniaxial strain on both the electrical and optical properties of vdW heterostructures and can be easily extended to include additional characterization techniques. 

Ultra-high purity elemental sources have long been considered a prerequisite for obtaining low impurity concentrations in compound semiconductors in the world of molecular beam epitaxy (MBE) since its inception in 1968. However, we demonstrate that a “dirty” solid precursor, ruthenium(III) acetylacetonate [also known as Ru(acac)3], can yield single-phase, epitaxial, and superconducting Sr2RuO4 films with the same ease and control as III–V MBE. A superconducting transition was observed at ∼0.9 K, suggesting a low defect density and a high degree of crystallinity in these films. In contrast to the conventional MBE, which employs the ultra-pure Ru metal evaporated at ∼2000 °C as a Ru source, along with reactive ozone to obtain Ru → Ru4+ oxidation, the use of the Ru(acac)3 precursor significantly simplifies the MBE process by lowering the temperature for Ru sublimation (less than 200 °C) and by eliminating the need for ozone. Combining these results with the recent developments in hybrid MBE, we argue that leveraging the precursor chemistry will be necessary to realize next-generation breakthroughs in the synthesis of atomically precise quantum materials. 

Abstract Fe 1+ y Te 1− x Se x is characterized by its complex magnetic phase diagram and highly orbital-dependent band renormalization. Despite this, the behavior of nematicity and nematic fluctuations, especially for high tellurium concentrations, remains largely unknown. Here we present a study of both B 1 g and B 2 g nematic fluctuations in Fe 1+ y Te 1− x Se x (0 ≤ x ≤ 0.53) using the technique of elastoresistivity measurement. We discovered that the nematic fluctuations in two symmetry channels are closely linked to the corresponding spin fluctuations, confirming the intertwined nature of these two degrees of freedom. We also revealed an unusual temperature dependence of the nematic susceptibility, which we attributed to a loss of coherence of the d x y orbital. Our results highlight the importance of orbital differentiation on the nematic properties of iron-based materials. 

Abstract Niobium chloride (Nb₃Cl₈) is a layered two-dimensional semiconducting material with many exotic properties including a breathing kagome lattice, a topological flat band in its band structure, and a crystal structure that undergoes a structural and magnetic phase transition at temperatures below 90 K. Despite being a remarkable material with fascinating new physics, the understanding of its phonon properties is at its infancy. In this study, we investigate the phonon dynamics of Nb₃Cl₈in bulk and few layer flakes using polarized Raman spectroscopy and density-functional theory (DFT) analysis to determine the material’s vibrational modes, as well as their symmetrical representations and atomic displacements. We experimentally resolved 12 phonon modes, five of which areA_1gmodes while the remaining seven areE_gmodes, which is in strong agreement with our DFT calculation. Layer-dependent results suggest that the Raman peak positions are mostly insensitive to changes in layer thickness, while peak intensity and full width at half maximum are affected. Raman measurements as a function of excitation wavelength (473–785 nm) show a significant increase of the peak intensities when using a 473 nm excitation source, suggesting a near resonant condition. Temperature-dependent Raman experiments carried out above and below the transition temperature did not show any change in the symmetries of the phonon modes, suggesting that the structural phase transition is likely from the high temperatureP $\overline{\text{3}m}$ 1 phase to the low-temperatureR $\overline{3m}$ phase. Magneto-Raman measurements carried out at 140 and 2 K between −2 and 2 T show that the Raman modes are not magnetically coupled. Overall, our study presented here significantly advances the fundamental understanding of layered Nb₃Cl₈material which can be further exploited for future applications.