Ultrafast spectroscopy under simultaneous high pressure and magnetic field provides a versatile approach for investigating pressure-driven electronic instabilities and correlated phases, and for probing potential bulk superconducting behavior under extreme conditions. However, such an experimental platform has yet to be implemented, standing as a roadblock to a fuller understanding of nonequilibrium superconductivity and vortex-controlled quasi-particle (QP) dynamics. Here, we bridge this capability gap by developing high pressure (up to 40 GPa), high magnetic field (up to 7 T), cryogenic (down to 5 K) femtosecond spectroscopy, and using it to probe magneto-pressure evolution of quasiparticle dynamics in the trilayer nickelate Pr_4Ni_3O_10. We observe pronounced critical slowing down of QP relaxation at the charge-density-wave transition, which collapses under applied pressure. At higher pressures, the relaxation instead lengthens at low temperature, consistent with incipient superconducting correlations. However, the negligibel magnetic-field-dependence up to 7 T and absence of vortex-induced pre-bottleneck dynamics–robust signatures observed in our controlled bulk superconducting samples–indicates that any superconducting state under the present pressure conditions is likely non-bulk, filamentary, or strongly inhomogeneous. The magneto-pressure ultrafast capability opens a new avenue for resolving outstanding questions surrounding pressure-induced superconductivity and intertwined orders in correlated quantum materials.

La2Ni7 is an itinerant magnetic system with a small ordered moment of similar to 0.1 & micro;B/Ni and a series of antiferromagnetic (AFM) transitions at T1 = 61.0 K, T2 = 56.5 K, and T3 = 42.2 K. M(H), and rho(H) isotherms as well as constant field M(T) and rho(T) measurements on single-crystalline samples manifest a complex, anisotropic H-T phase diagram with multiple phase lines. Here we present the growth and characterization of single crystals of the La2(CuxNi1-x)7 series for 0 x 0.181. We measured powder x-ray diffraction and composition, as well as anisotropic temperature-and field-dependent resistivity, temperature-and field-dependent magnetization, and temperature-dependent heat capacity on these single crystals. Using the measured data we infer a transition temperature-composition (T-x) phase diagram for this system to study the evolution of the AFM ordering upon Cu substitution. For 0 x 0.097, the system remains magnetically ordered at base temperature with x 0.012, showing signs of multiple AFM ordering temperatures. For the higher substitution levels 0.125 x 0.181, there are no signatures of magnetic ordering, but anomalous features in resistance and heat capacity data are observed which are consistent with the Kondo effect in this system. The intermediate x = 0.105 sample lies between the magnetic ordered and the Kondo regime and is in the vicinity of the AFM quantum critical point (QCP). Thus, La2(CuxNi1-x)7 is an example of a small moment system that can be tuned through a QCP. Given these data combined with the fact that the La2Ni7 structure has kagomelike, Ni sublattices running perpendicular to the crystallographic c axis, and a predicted 3d-electron flat band that contributes to the density of states near the Fermi energy, La2(CuxNi1-x)7 becomes a promising system to host and study exotic physics.

Scanning Tunneling Microscopy is a cornerstone technique for visualizing the electronic density of states with atomic resolution (typically below 0.1 nm). While the field of view of most STM setups extends up to a few microns, obtaining atomic resolution over these large areas is often impractical and excessively time-consuming. This is due to the need to acquire maps with a point number reaching 10^7 or more with a full current or conductance vs voltage curve at each point. The standard procedure is to make large scale maps and then select small regions to zoom-in for high-resolution atomic scale analysis. However, this approach fails to address a question which is often critical: Does a specific atomic-scale modulation of the electronic density of states persist over much larger, mesoscopic length scales? Here we present a new method: Replica STM (R-STM), that overcomes this limitation, allowing the study of atomic-scale phenomena up to micron length scales. We obtained new large-area STM tunneling conductance maps in UTe_2 and FeSe, spanning areas over 200 nm in size. In these large scale maps we discovered periodic signals with wavelengths significantly exceeding interatomic distances. We show that these large-wavelength periodic signals are replicas of the underlying atomic-scale density of states modulations. R-STM leverages these replica signals to efficiently track atomic-scale features over large areas. We discuss the influence of phase slips, disorder and defects in the replicas. Our results suggest that atomic scale modulations of the superconducting density of states could persist over large length scales in FeSe. R-STM provides a new capability for STM to compare atomic scale with micrometer scale phenomena. The proof of principle of R-STM can be extended to any other scanning probe microscopy experiment where a periodic signal is traced as a function of position.

Marcasite-type compounds have been proposed as promising hosts of exotic magnetic quantum states, yet experimental realizations in stoichiometric, disorder-free systems remain limited. Here, we report the high-pressure stabilization and magnetic characterization of MnSb_2, a marcasite-type compound that is thermodynamically metastable under ambient pressure. Single crystals were synthesized using a cubic multi-anvil press, and powder and single-crystal X-ray diffraction confirm the orthorhombic Pnnm structure. These crystals are stable at ambient pressure for a long time up to between 450-500 K. Heat-capacity measurements reveal phase transitions at approximately 220 K and 118 K. Neutron diffraction uncovers an unconventional magnetic ground state below 220 K. Magnetic powder neutron diffraction refinements reveal possible multiple magnetic configurations that provide comparably acceptable fits to the experimental data. While most solutions are consistent with a spin-density-wave (SDW) description, helical models systematically yield inferior agreement factors. Across a broad range of models, the Mn ordered moment reaches a maximum value of approximately 2 μ_B and remains predominantly collinear, with minimal canting along the c-axis. At 200 K, the magnetic propagation vector is q = (0, 0.3975, 0.3783); upon cooling, the b component increases toward 0.5, reflecting a temperature-dependent evolution of the modulation. The need for modification of the magnetic model between high and low temperatures further highlights the complex and strongly temperature-dependent nature of the magnetic order in this system. These results establish MnSb_2 as a pressure-stabilized marcasite magnet with a highly tunable, complex magnetic ground state and a compelling stoichiometric platform for exploring unconventional magnetic behavior, including potential altermagnetism.

Two-dimensional van der Waals (vdW) magnets are attracting significant attention, both as platforms for studying fundamental magnetic interactions and for the exciting possibility of utilizing them as building blocks in devices and heterostructures, which may lead to new physical phenomena and functionalities. Here, we provide a detailed study of the crystal structure and physical properties of the recently discovered vdW ferromagnet FePd2Te2. We find this compound has a relatively wide width of formation, and grow single crystals with compositions FexPdyTe2 where x ranges from 0.9 to 1.1 and y from 1.8 to 2.5, respectively. Temperature-dependent X-ray diffraction and transport measurements reveal that a first-order structural transition occurs in the range of T = 360-420 K, where the critical temperature, modulation wave vector, and corresponding room-temperature crystal structures all depend on chemical composition. Above the transition, the compounds with Pd fraction y > 2 adopt a disordered derivative of the tetragonal FeTe structure, with the Fe layer showing mixed Fe/Pd occupancy and the extra Pd atoms partially occupying interstitial sites. Below 370 K, the structure is incommensurately modulated, likely associated with the complex ordering of Pd/Fe atoms in the metal layers or the interstitial Pd in the vdW gaps. For y < 2, the composition Fe1.1Pd1.8Te2 has monoclinic symmetry at room temperature that is consistent with the reported structure of FePd2Te2. This phase undergoes a structural transition at 420 K for which the high temperature structure is yet to be determined; however, based on the similarities with the y > 2 compounds, we speculate that its T > 420 K structure is also tetragonal. Importantly, the high temperature, symmetry-breaking structural transition observed here provides a likely explanation for the origin of the structural domains previously observed in FePd2Te2. All compounds investigated in the FexPdyTe2 series show metallic behavior, with magnetic characterization indicating that they are easy-plane, hard, ferromagnets with T-C spanning 98-180 K. Both the critical temperature for the structural transition and the Curie temperature are moderately suppressed with increasing Pd fraction y and corresponding decreasing Fe fraction x, indicating that synthetic control over x and y paves way for the further exploration of these compounds.

LaCrGe3 is a metallic, itinerant ferromagnet with T-C approximate to 86 K and an easy magnetic direction along its hexagonal c axis. Here we present studies of the H||c Hall effect in LaCrGe(3 )at ambient pressure and under pressures up to 24 kbar. At ambient pressure the anomalous Hall conductivity in the ferromagnetic state reaches a large value of similar to 520 Omega(-1 )cm(-1). The overall data are consistent with the behavior expected for a ferromagnet with magnetic field applied along its easy axis. Measurements under pressure yield an H = 0, P-T phase diagram consistent with earlier publications with T-C being suppressed with pressure and nonferromagnetic phases appearing for P> 15 kbar. The data suggest that the observed T-C suppression is due to the pressure-dependent exchange interactions rather than suppression of the size of the magnetic moment. Field-dependent Hall resistivity in the higher-pressure, nonferromagnetic state is consistent with the net moment being zero for H = 0. In a finite field there is a sharp anomaly comparable to the one associated with a spin-flip metamagnetic transition. The H-T phase diagrams corresponding to a pressure-induced magnetic phase are constructed for several pressures. The Hall data suggest the possibility of the pressure-induced nonferromagnetic phase being a combination of multiple small regions of antiferromagnetic phases with different wave vectors.

The compound SrNi_2P_2 can exhibit multiple crystal structures with no P-P pairs bonded (uncollapsed tetragonal, or ucT, state), with one-third of the P-P pairs bonded (one-third collapsed orthorhombic, or tcO, state), or with all P-P pairs bonded (collapsed tetragonal, or cT, state) across the Sr layers. The system can be tuned into its different states by changing temperature, mechanical stress, or chemical composition. Changes in bonding may manifest in changes of macroscopic properties of the material, such as its shape, electrical conductivity, or magnetism. In this work, we show that SrNi_2P_2 can be tuned among the three states by changing Cu substitution and temperature. We present temperature-dependent resistance and single-crystal x-ray diffraction results in Sr(Ni_1-xCu_x)_2P_2 single-crystals that show that Cu substitution favors the P-P bonding, stabilizing the cT state at ambient pressure. We construct a T-x phase diagram that shows how all of these transition temperatures increase with increasing Cu fraction, x. The transition between the tcO state and the cT state exhibits a very large thermal hysteresis, which can be tuned to temperatures close to room temperature. In particular, the properties of Sr(Ni_0.963Cu_0.037)_2P_2 may make it suitable for applications as a shape memory material at room temperature.

Type-II superconductors under magnetic fields are in a quantum coherent non-dissipative state as long as vortices remain pinned. Dissipation appears when vortices depin, eventually driven by thermal fluctuations. This can be associated to a melting transition between a vortex solid and a vortex liquid. This transition is almost always observed very close to T$_c$ when probed by macroscopic experiments. However, it remains unclear how the vortex solid responds to thermal fluctuations at the scale of individual vortices far from the melting transition. Here we use scanning tunneling microscopy (STM) to visualize vortices in CaKAs$_4$Fe$_4$ (T$_c \approx$ 35 K). We find vortex liquid droplets-localized regions in space where vortices strongly fluctuate due to thermal exctiation-at temperatures as low as 0.5\,T$_c$. Our results show that the onset of dissipation at the local scale occurs at temperatures considerably below T$_c$ in type-II superconductors.

Chalcogenides-rich transition metal compounds host a rich landscape of emergent quantum phenomena that are intimately governed by their quasi-one-dimensional chemical-bonding frameworks and their response to external perturbations such as pressure. Here, we report a pressure-induced iso-symmetric structural transition in the quasi-one-dimensional compound CrNbSe_5, in which the electronic ground state is controlled not by symmetry breaking but by a continuous reorganization of local bonding interactions. Applied pressure reversibly tunes CrNbSe_5 between semiconducting and semimetallic states, enabling access to low- and high-carrier electronic regimes through direct modulation of metal-chalcogen bonding. High-pressure single-crystal X-ray diffraction directly resolves the evolution of Cr-Se and Nb-Se bond distances, coordination polyhedra, and connectivity, revealing a fully reversible semimetal-semiconductor-semimetal transition driven by gradual yet cooperative bond rearrangements within a preserved crystallographic symmetry. In contrast to chemical substitution, which irreversibly alters composition and introduces disorder, pressure acts as a clean, continuous control parameter that reshapes the bonding landscape without disrupting structural symmetry. These results establish CrNbSe_5 as a model system for electronically driven phase switching via tunable chemical bonding, highlighting iso-symmetric bond reorganization as a powerful design principle for pressure-controlled electronic and spintronic functionalities.

Cerium diantimonide (CeSb2) is a layered heavy-fermion Kondo lattice material that hosts complex magnetism and pressure-induced superconductivity. The interpretation of its in-plane anisotropy has remained unsettled due to structural twinning, which superimposes orthogonal magnetic responses. Here we combine controlled crystal growth with magnetization and rotational magnetometry to disentangle the effects of twinning. Nearly untwinned high-quality single crystals reveal the intrinsic in-plane anisotropy: The in-plane easy axis saturates at Measy(4 T) approximate to 1.8 & micro;B/Ce, while the in-plane hard axis magnetization is strongly suppressed, nearly linear, and comparable to the out-of-plane response. These results resolve long-standing discrepancies in reported magnetic measurements, in which in-plane metamagnetic transition fields and saturation magnetization varied significantly across previous studies. Growth experiments demonstrate that avoiding the proposed alpha 3 structural transition-through Sb-rich flux and slower cooling-systematically reduces twinning. However, powder x-ray diffraction and differential thermal analysis measurements show no clear evidence of a distinct 3 phase. Our results establish a consistent magnetic phase diagram and provide essential constraints for crystal-electric field models, enabling a clearer understanding of the interplay between anisotropic magnetism and unconventional superconductivity in CeSb2.

We report the discovery of a ternary compound, Eu0.8Pt6Al16.4. We determine its chemical and structural characteristics based on energy-dispersive X-ray spectroscopy as well as both powder and single-crystal X-ray diffraction, demonstrating that it crystallizes in a hexagonal structure type EuPt6Al17 with no reported structural analog. The temperature- and field-dependent magnetization, and temperature-dependent resistance measurements, reveal that the Eu2+ magnetic moments order antiferromagnetically below 2.8 K.

The layered compound γ-PtBi_{2} is a topological semimetal with Fermi arcs at the surface joining bulk Weyl points. Recent work has found signatures of surface superconductivity consisting of gap openings compatible with a critical temperature orders of magnitude larger than the bulk value. However, no superconducting vortices have been identified, raising questions about the robustness of the phase coherence. Here, we use very low temperature STM and find robust superconductivity with T_{C}=2.9  K and H_{C2}≈1.8  T linked to the Fermi arcs. We observe quantized superconducting vortices and the Josephson effect, demonstrating two-dimensional macroscopic quantum phase coherence.

Dirac semimetals of the form AMnX_2 (A = alkaline-earth or divalent rare earth; X = Bi, Sb) host conducting square-net Dirac-electron layers of X atoms interleaved with antiferromagnetic MnX layers. In these materials, canted antiferromagnetism can break time-reversal symmetry (TRS) and produce a Weyl semimetallic state. CaMnBi_2 was proposed to realize this behavior below T^*∼ 50 K, where anomalies in resistivity and optical conductivity were reported. We investigate single-crystal CaMnBi_2 using polarized and unpolarized neutron diffraction, x-ray diffraction, and density functional theory (DFT) calculations to elucidate the underlying crystal and magnetic structures. The results show that the observed anomalies do not originate from spin canting or weak ferromagnetism; no measurable uniform Mn spin canting is detected. Instead, CaMnBi_2 undergoes a coupled structural and magnetic symmetry-lowering transition at T^* = 46(2) K, from a tetragonal lattice with C-type antiferromagnetism to an orthorhombic phase with unit-cell doubling along the c axis and minimal impact on magnetism. Analysis of superlattice peak intensities and lattice distortion reveals a continuous second-order transition governed by a single order parameter. The refined atomic displacements correspond to a zigzag bond-order-wave (BOW) modulation of Bi-Bi bonds, consistent with an electronically driven Peierls-type instability in the Dirac-electron Bi layer, long anticipated by Hoffmann and co-workers [W. Tremel and R. Hoffmann, J. Am. Chem. Soc. 109, 124 (1987); G. A. Papoian and R. Hoffmann, Angew. Chem. Int. Ed. 39, 2408 (2000)].

The appearance of spontaneous charge order in chemical systems is often associated with the emergence of novel, and useful, properties. Here we show through single crystal diffraction that the Eu ions in the mixed valent metal EuPd$_3$S$_4$ undergo long-range charge ordering at $T_{\mathrm{CO}} = 340 \mathrm{~K}$ resulting in simple cubic lattices of Eu$^{2+}$ ($J = 7/2$) and Eu$^{3+}$ ($J = 0$) ions. As only one of the two sublattices has a non-magnetic ground state, the charge order results in the emergence of remarkably simple G-type antiferromagnetic order at $T_{\mathrm{N}} = 2.85(6) \mathrm{~K}$, observed in magnetization, specific heat, and neutron diffraction. Application of a $0.3 \mathrm{~T}$ field is sufficient to induce a spin flop transition to a magnetically polarized, but still charge ordered, state. Density functional theory calculations show that this charge order also modifies the electronic degeneracies present in the material: without charge order, EuPd$_3$S$_4$ is an example of a double Dirac material containing 8-fold degenerate electronic states, greater than the maximum degeneracy of six possible in molecular systems. The symmetry reduction from charge order transmutes 8-fold double Dirac states into 4-fold Dirac states, a degeneracy that can be preserved even in the presence of the magnetic order. Our results show not only how charge order can be used to produce interesting magnetic lattices, but also how it can be used to engineer controlled degeneracies in electronic states.

Non-magnetic FeNb_3Se_10 has been demonstrated to be an insulator at ambient pressure through both theoretical calculations and experimental measurements and it does not host topological surface states. Here we show that on the application of pressure, FeNb_3Se_10 transitions to a metallic state at around 3.0 GPa. With a further increase in pressure, its resistivity becomes independent of both temperature and pressure. Its crystal structure is maintained to at least 4.4 GPa.

TbV_6Sn_6 is a topological metal where ferromagnetic Tb ions with strong uniaxial magnetic anisotropy interact with V kagome layers. Inelastic neutron scattering (INS) measurements show that the Tb ions adopt an Ising doublet ground state. Here, we consider whether a transverse magnetic field can drive TbV_6Sn_6 toward a quantum critical point, providing a rare example of transverse-field Ising criticality in a metallic compound. High-field magnetization measurements reveal a first-order-like spin-reorientation transition at 25.6 T. Our INS-based magnetic model finds that this is caused by an avoided crossing of an excited-state singlet with the ground-state doublet. Surprisingly, our model predicts that quantum critical and tricritical points are accessible within the range of experimentally determined model parameters and may be reached by varying the direction of an applied magnetic field.

We present high pressure electrical transport, magnetization, and single crystal X-ray diffraction data on SrCo2P2 single crystals. X-ray diffraction data show that there is a transition to a collapsed tetragonal structure for p > 10 GPa and measurements of resistance show that above 10 GPa, a clear transition-like feature can be observed at temperatures up to 260 K. Further magnetization, magnetoresistance and Hall measurements made under pressure all indicate that this transition is to a ferromagnetic ground state. First principles-based density functional theory (DFT) calculations also show that there is a first-order transition between tetragonal and collapsed tetragonal (cT) phases, with an onset near 10 GPa as well as the appearance of the ferromagnetic (FM) ordering in the cT phase. Above 30 GPa, the experimental signatures of the magnetic ordering vanish in a first-order-like manner, consistent with the theoretical calculation results, indicating that SrCo2P2 is another example of the avoidance of quantum criticality in ferromagnetic intermetallic compounds. SrCo2P2 provides clear evidence that the structural, electronic and magnetic properties associated with the cT transition are strongly entangled and are not only qualitatively captured by our first principles-based calculations but are quantitatively reproduced as well.

The recent availability of step-edge, frit-disc crucible sets (generally sold as Canfield Crucible Sets or CCS) has led to multiple innovations associated with our group's use of solution growth. Use of CCS allows for the clean separation of liquid from solid phases during the growth process. This clean separation enables the reuse of the decanted liquid, either allowing for simple, economic, savings associated with recycling expensive precursor elements or allowing for the fractionation of a growth into multiple, small steps, revealing the progression of multiple solidifications. Clean separation of liquid from solid phases also allows for the determination of the liquidus line (or surface) and the creation, or correction, of composition-temperature phase diagrams. The reuse of clean decanted liquid has also allowed us to prepare liquids ideally suited for the growth of large single crystals of specific phases by tuning the composition of the melt to the optimal composition for growth of the desired phase, often with reduced nucleation sites. Finally, we discuss how solution growth and CCS use can be harnessed to provide a plethora of composition-temperature data points defining liquidus lines or surfaces with differing degrees of precision to either test or anchor artificial intelligence and/or machine learning based attempts to augment and extend the limited experimentally determined data base.

WTe2 stands out as a semimetal presenting Fermi level quantum oscillations in most measured quantities under magnetic fields. However, the electronic band structure above and below the Fermi level has not been completely explored. Here we study the electronic band structure of WTe2 by quasiparticle interference with scanning tunneling microscopy and observe, with the support of density functional theory, the electron and hole bands around the Fermi level. We also report on the observation of Landau quantization in atomically resolved measurements and discuss the possible connection with band structure calculations.

LaRu3Si2 is of current research interest as a kagome metal with a superconducting transition temperature, Tc similar to 7 K, and higher-temperature charge density wave orders. Here we report on electrical transport and x-ray diffraction measurements on LaRu3Si2 under pressure up to 65 GPa and 35 GPa, respectively. The superconducting transition temperature Tc first gets slightly enhanced and reaches a maximum similar to 8.7 K at similar to 8.5 GPa. With further applied pressure, Tc 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 similar to 11.5 GPa, and further to a structure with lower symmetry above similar to 23.5 GPa. These transition pressures roughly correlate with features found in our pressure-dependent transport data.