The coexistence of charge density wave (CDW) and superconductivity in tantalum disulfide (2H−TaS2) at low temperature is boosted by applying hydrostatic pressures to study both vibrational and ...magnetic transport properties. Around Pc, we observe a superconducting dome with a maximum superconducting transition temperature Tc=9.1 K. First-principles calculations of the electronic structure predict that, under ambient conditions, the undistorted structure is characterized by a phonon instability at finite momentum close to the experimental CDW wave vector. Upon compression, this instability is found to disappear, indicating the suppression of CDW order. The calculations reveal an electronic topological transition (ETT), which occurs before the suppression of the phonon instability, suggesting that the ETT alone is not directly causing the structural change in the system. The temperature dependence of the first vortex penetration field has been experimentally obtained by two independent methods. While a d wave and single-gap BCS prediction cannot describe the lower critical field Hc1 data, the temperature dependence of the Hc1 can be well described by a single-gap anisotropic s-wave order parameter.
ZrSiS has recently gained attention due to its unusual electronic properties: nearly perfect electron-hole compensation, large, anisotropic magnetoresistance, multiple Dirac nodes near the Fermi ...level, and an extremely large range of linear dispersion of up to ~2 eV. We carried out a series of high pressure electrical resistivity measurements on single crystals of ZrSiS. Shubnikov-de Haas measurements show two distinct oscillation frequencies. For the smaller orbit, we observe a change in the phase of ~0.5, which occurs between 0.16–0.5 GPa. This change in phase is accompanied by an abrupt decrease of the cross-sectional area of this Fermi surface. We attribute this change in phase to a possible topological quantum phase transition. The phase of the larger orbit exhibits a Berry phase of π and remains roughly constant up to ~2.3 GPa. Resistivity measurements to higher pressures show no evidence for pressure-induced superconductivity to at least ~20 GPa.
Using a membrane-driven diamond anvil cell and both ac magnetic susceptibility and electrical resistivity measurements, we have characterized the superconducting phase diagram of elemental barium to ...pressures as high as 65 GPa. We have determined the superconducting properties of the recently discovered Ba-VI crystal structure, which can only be accessed via the application of pressure at low temperature. We find that Ba-VI exhibits a maximum Tc near 8 K, which is substantially higher than the maximum Tc found when pressure is applied at room temperature. We discuss our results in terms of the implications for pressure-induced superconductivity in other elements exhibiting complex/modulated structures at high pressure. Finally, we highlight the potential of cryogenic compression to reveal additional richness in previously explored high-pressure phase diagrams.
The correlated electron material CePd2 P2 crystallizes in the ThCr2 Si2 structure and orders ferromagnetically at 29 K. Prior work by Lai et al. Phys. Rev. B 97, 224406 (2018) found evidence for a ...ferromagnetic quantum critical point induced by chemical compression via substitution of Ni for Pd. However, disorder effects due to the chemical substitution interfere with a simple analysis of the possible critical behavior. In the present paper, we examine the temperature-pressure-magnetic-field phase diagram of single crystalline CePd2 P2 to 25 GPa using a combination of resistivity, magnetic susceptibility, and x-ray diffraction measurements. We find that the ferromagnetism appears to be destroyed near 12 GPa, without any change in the crystal structure.