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Strain is ubiquitous in solid-state materials, but despite its fundamental importance and technological relevance, leveraging externally applied strain to gain control over material properties is still in its infancy. In particular, strain control over the diverse phase transitions and topological states in two-dimensional transition metal dichalcogenides remains an open challenge. Here, we exploit uniaxial strain to stabilize the long-debated structural ground state of the 2D topological semimetal IrTe 2 , which is hidden in unstrained samples. Combined angle-resolved photoemission spectroscopy and scanning tunneling microscopy data reveal the strain-stabilized phase has a 6 × 1 periodicity and undergoes a Lifshitz transition, granting unprecedented spectroscopic access to previously inaccessible type-II topological Dirac states that dominate the modified inter-layer hopping. Supported by density functional theory calculations, we show that strain induces an Ir to Te charge transfer resulting in strongly weakened inter-layer Te bonds and a reshaped energetic landscape favoring the 6×1 phase. Our results highlight the potential to exploit strain-engineered properties in layered materials, particularly in the context of tuning inter-layer behavior. Uniaxial strain is a powerful approach to tune material properties and select between nearly degenerate phases. Here, uniaxial strain is used to stabilize the elusive 6×1 charge ordered ground state of IrTe 2 , revealing insights into its electronic structure and type-II topological Dirac states.

The interplay between superconductivity and charge or spin order is a key focus in condensed matter physics, with kagome lattice systems providing unique insights. The kagome superconductor LaRu 3 Si 2 ( T c  ≃ 6.5 K) features a characteristic kagome band structure and a hierarchy of charge order transitions at T co,I  ≃ 400 K and T co,II  ≃ 80 K, along with an additional transition at T * ≃ 35 K associated with electronic and magnetic responses. Using magnetotransport under pressure up to 40 GPa, we find T c peaks at 9 K (2 GPa)—the highest among kagome superconductors—remains nearly constant up to 12 GPa, and then decreases to 2 K at 40 GPa, forming a dome-shaped phase diagram. Similarly, both the resistivity anomaly at T * and the magnetoresistance exhibit a dome-shaped pressure dependence. Moreover, above 12 GPa, X-ray diffraction reveals that the charge order evolves from long-range to short-range, coinciding with the suppression of T c . These observations indicate that superconductivity in LaRu 3 Si 2 is closely linked to the charge-ordered state and the electronic responses at T co,II and T *. The authors study kagome superconductor LaRu3Si2 under pressure up to 40 GPa. They find a superconducting dome as a function of pressure, with Tc reaching its maximum when the coexisting charge order remains long-range.

The interplay between superconductivity and charge or spin order is a key focus in condensed matter physics, with kagome lattice systems providing unique insights. The kagome superconductor LaRu Si (T  ≃ 6.5 K) features a characteristic kagome band structure and a hierarchy of charge order transitions at T  ≃ 400 K and T  ≃ 80 K, along with an additional transition at T* ≃ 35 K associated with electronic and magnetic responses. Using magnetotransport under pressure up to 40 GPa, we find T peaks at 9 K (2 GPa)-the highest among kagome superconductors-remains nearly constant up to 12 GPa, and then decreases to 2 K at 40 GPa, forming a dome-shaped phase diagram. Similarly, both the resistivity anomaly at T* and the magnetoresistance exhibit a dome-shaped pressure dependence. Moreover, above 12 GPa, X-ray diffraction reveals that the charge order evolves from long-range to short-range, coinciding with the suppression of T . These observations indicate that superconductivity in LaRu Si is closely linked to the charge-ordered state and the electronic responses at T and T*.

\\(\\)-Carbide-type compounds have recently emerged as a diverse class of materials in the study of superconductivity. These phases contribute to a growing family of metal-rich quantum materials that exhibit unusual superconducting properties emerging from complex metallic bonding. Several members of the \\(\\)-carbide-type phases have been found to be bulk superconductors -- such as Nb\\(_4\\)Rh\\(_2\\)C\\(_1-\\), Ta\\(_4\\)Rh\\(_2\\)C\\(_1-\\), Ti\\(_4\\)Ir\\(_2\\)O\\(_1-\\), and Ti\\(_4\\)Co\\(_2\\)O\\(_1-\\) -- with transition temperatures up to \\(T_ c \\) 10 K and upper critical fields as high as \\(_0 H_ c2(0) \\) 30 T. Whereas the transition temperatures may fall within the range typical for intermetallic superconductors, the pronounced violation of the weak-coupling Pauli limit in many of these crystallographically high-symmetry materials is noteworthy. Here, we review recent progress on superconducting \\(\\)-carbide-type phases, emphasizing how crystal symmetry, synthetic challenges, transition-metal composition, and electronic structure govern their superconducting properties. Furthermore, we outline open questions and future directions, including the possible discovery of new \\(\\)-carbide-type materials.

Pyrite, also known as fool's gold is the thermodynamic stable polymorph of FeS\\(_2\\). It is widely considered as a promising d-band semiconductor for various applications due to its intriguing physical properties. Marcasite is the other naturally occurring polymorph of FeS\\(_2\\). Measurements on natural crystals have shown that it has similarly promising electronic, mechanical, and optical properties as pyrite. However, it has been only scarcely investigated so far, because the laboratory-based synthesis of phase-pure samples or high-quality marcasite single crystal has been a challenge until now. Here, we report the targeted phase formation via hydrothermal synthesis of marcasite and pyrite. The formation condition and phase purity of the FeS\\(_2\\) polymorphs are systematically studied in the form of a comprehensive synthesis map. We, furthermore, report on a detailed analysis of marcasite single crystal growth by a space-separated hydrothermal synthesis. We observe that single phase product of marcasite forms only on the surface under the involvement of H\\(_2\\)S and sulphur vapor. The availability of high-quality crystals of marcasite allows us to measure the fundamental physical properties, including an allowed direct optical bandgap of 0.76 eV, temperature independent diamagnetism, an electronic transport gap of 0.11 eV, and a room-temperature carrier concentration of 4.14 \\(\\) 10\\(^18\\) cm\\(^-3\\). X-ray absorption/emission spectroscopy are employed to measure the band gap of the two FeS\\(_2\\) phases. We find marcasite has a band gap of 0.73 eV, while pyrite has a band gap of 0.87 eV. Our results indicate that marcasite -- that is now synthetically available in a straightforward fashion -- is as equally promising as pyrite as candidate for various semiconductor applications based on earth abundant elements.

We report on the discovery of superconductivity in the previously unknown compound Ta\\(_4\\)Rh\\(_2\\)C\\(_1-\\). Ta\\(_4\\)Rh\\(_2\\)C\\(_1-\\) crystallizes in the \\(\\)-carbide structure type, in the cubic space group \\(Fd3m\\) (No.227) with a unit cell parameter of \\(a = \\) 11.7947 Temperature-dependent magnetic susceptibility, resistivity, and specific heat capacity measurements reveal that Ta\\(_4\\)Rh\\(_2\\)C\\(_1-\\) is a type-II bulk superconductor with a critical temperature of \\(T_ c\\) = 6.4 K, and a normalized specific heat jump \\( C/ T_ c\\) = 1.56. Notably, we find Ta\\(_4\\)Rh\\(_2\\)C\\(_1-\\) has a high upper critical field of \\(_0 H_ c2 (0)\\) = 17.4 T, which is exceeding the BCS weak coupling Pauli limit of \\(_0 H_ Pauli\\) = 11.9 T.

We report on the pressure dependence of superconducting transition temperature Tc and upper critical field Bc2(0) through electrical transport of the Ti4Co2O superconductor (eg.,the superconducting transition temperature Tc = 2.5 K and the Bc2(0)=7.2T=2.9Tc). We find that the Tc exhibits non-monotonic pressure dependence:it rises monotonically at first with a pressure coefficient of dTc/dP=0.034 K/GPa, but rapidly decreases around 10-20 GPa, and then increases with the dTc/dP = 0.023 K/GPa, up to= 4.31 K at 69.7 GPa. Concurrently, the Bc2(0)exhibits a dome shaped pressure dependence, with its maximum at 5 GPa of almost twice the value at ambient pressure, exceeding the weak-coupling Pauli paramagnetic limit Bp throughout the whole pressure range. By comparing the normal-state and superconducting properties, we identify two distinct superconducting regimes, with a low-pressure superconducting phase characterized by an enhanced Bc2(0)values and Fermi-liquid normal-state electrical transport (the exponent n = 2), and a high-pressure superconducting phase with a monotonically increased Tc and an enhancement in phonon scatterings (the exponent n = 4). Room-temperature synchrotron X-ray diffraction indicates that there is no structural transition up to 55.8 GPa, which gives a relatively large bulk modulus of 192 GPa in comparison with other alloy superconductors. First-principles calculations suggest that the nonmonotonic Tc maybe closely related to the evolution of the density of states of Ti4Co2O upon compression, which is different from those of isostructural superconductors Ti4Ir2O and Nb4Rh2C. Our results show that even in the Ti4Co2O with weak spin-orbit coupling, superconductivity remains highly sensitive to the external stimuli such as pressure.

Here we report muon spin rotation (muSR) experiments on the temperature and field dependence of the effective magnetic penetration depth (lambda) in the eta-carbide-type suboxide Ti4Ir2O, a superconductor with an considerably high upper critical field. Temperature dependence of penetration depth, obtained from transverse-field (TF)-muSR measurements, is in perfect agreement with an isotropic fully gaped superconducting state. Furthermore, our ZF muSR results confirm that the time-reversal symmetry is preserved in the superconducting state. We find, however, a notably low ratio of 1.22 between the superconducting critical temperature and the superfluid density. This value is close to most unconventional superconductors, showing that a very small superfluid density is present in the superconducting state of Ti4Ir2O. The presented results will pave the way for further theoretical and experimental investigations to obtain a microscopic understanding of the origin of such a high upper critical field in an isotropic single gap superconducting system.

RhBi\\(_2\\) is a polymorphic system that exhibits two distinct phases. RhBi\\(_2\\) in the triclinic phase has been identified as a weak topological insulator with a van Hove singularity point close to the Fermi energy. Thus, triclinic RhBi\\(_2\\) is expected to exhibit exotic quantum properties under strain or pressure. In this study, we report on the emergence of superconductivity in the monoclinic RhBi\\(_2\\) under external pressures. The electrical resistivity behavior of the monoclinic RhBi\\(_2\\) single crystal is studied at a wide range of applied external pressures up to 40 GPa. We observe a pressure-induced superconductivity with a dome-shaped dependence of the critical temperature on pressure at pressures above 10 GPa. A maximum critical temperature (\\(T_c\\)) value of \\(T_c\\) = 5.1 K is reached at the pressure of 16.1 GPa. Furthermore, we performed detailed ab initio calculations to understand the electronic band structures of monoclinic RhBi\\(_2\\) under varying pressures. The combination of topology and pressure-induced superconductivity in the RhBi\\(_2\\) polymorphic system may provide us with a new promising material platform to investigate topological superconductivity.

TThe isotope effect is a powerful probe of electron-phonon interactions in solid-state systems, offering key insights into how atomic mass influences emergent quantum states. Here, the impact of oxygen isotope substitution (\\(^16 O \\; ^18 O\\)) on charge- and spin-density wave (CDW and SDW) transitions in the double-layer Ruddlesden-Popper nickelate La\\(_3\\)Ni\\(_2\\)O\\(_7\\) is investigated. A clear isotope effect is observed in the CDW transition: the transition temperature (\\(T_ CDW\\)) increases upon \\(^18\\)O substitution. In contrast, the SDW transition temperature remains unaffected within experimental uncertainty. These findings point to a strong involvement of lattice vibrations in the formation of charge order, while spin order appears to be predominantly of electronic origin. The results suggest that electron-phonon coupling, manifested through the CDW response to isotope substitution, may be relevant to the superconducting pairing mechanism in Ruddlesden-Popper nickelates.