We present a comprehensive study of the inhomogeneous mixed-valence compound, EuPd ₃ S ₄ , by electrical transport, X-ray diffraction, time-domain ¹⁵¹ Eu synchrotron Mössbauer spectroscopy, and X-ray absorption spectroscopy measurements under high pressure. Electrical transport measurements show that the antiferromagnetic ordering temperature, T _N , increases rapidly from 2.8 K at ambient pressure to 23.5 K at ~19 GPa and plateaus between ~19 and ~29 GPa after which no anomaly associated with T _N is detected. A pressure-induced first-order structural transition from cubic to tetragonal is observed, with a rather broad coexistence region (~20 GPa to ~30 GPa) that corresponds to the T _N plateau. Mössbauer spectroscopy measurements show a clear valence transition from approximately 50:50 Eu ²⁺ :Eu ³⁺ to fully Eu ³⁺ at ~28 GPa, consistent with the vanishing of the magnetic order at the same pressure. X-ray absorption data show a transition to a fully trivalent state at a similar pressure. Our results show that pressure first greatly enhances T _N , most likely via enhanced hybridization between the Eu 4 f states and the conduction band, and then, second, causes a structural phase transition that coincides with the conversion of the europium to a fully trivalent state.

The effect of pressure on the low-temperature states of the ${\mathrm{Re}}_3{\mathrm{Ge}}_7$ is investigated by both electrical and Hall resistance and magnetization measurements. At ambient pressure, the temperature-dependent resistance of ${\mathrm{Re}}_3{\mathrm{Ge}}_7$ behaves quasilinearly from room temperature down to 60 K, then undergoes a two-step metal-to-insulator transition (MIT) at temperatures $T_1=59.4\mathrm{K}$ and $T_2=58.7\mathrm{K}$, which may be related to a structural phase transition or occurrence of charge-density wave ordering. Upon applying pressure, the two-step ($T_1,T_2)$ MIT splits into three steps ($T_1,T_2$. and $T_3$) above 1 GPa, and all traces of MITs are fully suppressed by ∼8 GPa. Subsequently, the onset of bulk superconductivity (SC) occurs between 10.8 and 12.2 GPa and persists to our highest pressure of 26.8 GPa. At 12.2 GPa the superconducting transition temperature, $T_c$, and upper critical field, $H_{c}2$ reach the maximum of ${\mathrm{T}}_{\mathrm{c}}$ (onset) ∼5.9 K and $H_{c}2$ (1.8 K) ∼14 kOe. Our results not only present the observation of SC under high pressure in ${\mathrm{Re}}_3{\mathrm{Ge}}_7$ but also delineate the interplay between SC and other competing electronic states by creating a T-p phase diagram for this potentially topologically nontrivial system ${\mathrm{Re}}_3{\mathrm{Ge}}_7$.

The research on supercurrent diodes has surged rapidly due to their potential applications in electronic circuits at cryogenic temperatures. To unlock this functionality, it is essential to find supercurrent diodes that can work consistently at zero magnetic field and under ubiquitous stray fields generated in electronic circuits. However, a supercurrent diode with robust field tolerance is currently lacking. Here, we demonstrate a field-resilient supercurrent diode by incorporating a 2D multiferroic material into a Josephson junction, and observed a pronounced supercurrent diode effect at zero magnetic field. More importantly, the supercurrent rectification persists over a wide and bipolar magnetic field range beyond industrial standards for field tolerance. By theoretically modeling a multiferroic Josephson junction, we unveil that the interplay between spin-orbit coupling and multiferroicity underlies the unusual field resilience of the observed diode effect. This work introduces multiferroic Josephson junctions as a new field-resilient superconducting device for cryogenic electronics.

${\mathrm{LaRu}}_{3}{\mathrm{Si}}_{2}$ is of current research interest as a kagome metal with a superconducting transition temperature, ${T}_{c}\ensuremath{\sim}7$ K, and higher-temperature charge density wave orders. Here we report on electrical transport and x-ray diffraction measurements on ${\mathrm{LaRu}}_{3}{\mathrm{Si}}_{2}$ under pressure up to 65 GPa and 35 GPa, respectively. The superconducting transition temperature ${T}_{c}$ first gets slightly enhanced and reaches a maximum $\ensuremath{\sim}8.7$ K at $\ensuremath{\sim}8.5$ GPa. With further applied pressure, ${T}_{c}$ is initially gradually suppressed, then more rapidly suppressed, followed by gradual suppression, revealing a superconducting dome. Two possible pressure-induced structural phase transitions are also observed at room temperature, from the original hexagonal phase to another hexagonal structure above $\ensuremath{\sim}11.5$ GPa, and further to a structure with lower symmetry above $\ensuremath{\sim}23.5$ GPa. These transition pressures roughly correlate with features found in our pressure-dependent transport data.

In an extension of our previous work, (Bud’ko et al 2023 Supercond. Sci. Technol. 36 115001) the measurements of temperature dependent magnetization associated with trapped magnetic flux in a small single crystal of CaKFe₄As₄, using zero—field—cooled and field—cooled protocols were performed, on the same crystal, at ambient pressure without a pressure cell and at 2.2 GPa in a commercial diamond anvil cell (DAC), showing comparable results. The data show that with a proper care and understanding, trapped flux measurements in superconductors indeed can be performed on samples in DACs under pressure, as was done on superhydrides (Minkov et al 2023 Nat. Phys. 19 1293).

${\mathrm{CePd}}_3{\mathrm{S}}_4$ exhibits interplay between ferromagnetism (FM), quadrupolar order, and the Kondo effect at low temperatures with a FM transition temperature that is much higher than the value expected from the de Gennes scaling of the heavier $R{\mathrm{Pd}}_3{\mathrm{S}}_4$ compounds. In this work, we investigated the electrical transport and magnetic properties of ${\mathrm{CePd}}_3{\mathrm{S}}_4$ under pressure up through 12 GPa to better understand the interplay between electronic and magnetic phases in this material. Our findings show that the low-pressure FM state is suddenly replaced by a magnetically ordered phase that is most likely antiferromagnetic that spans from $\sim 7$ to $\sim 11$ GPa. Whereas this could be described as an example of avoided quantum criticality, given that clear changes in resistance and Hall data are detected near 6.3 GPa for all temperatures below 300 K, it is also possible that the change in ground state is a response to a pressure-induced change in structure. The lack of any discernible change in the pressure dependence of the room-temperature unit-cell parameter-volume across this whole pressure range suggests that this change in structure is either more subtle than could be detected by our measurements (i.e., development of weak wave vector) or the transition is electronic (such as a Lifshitz transition).