82 research outputs found

    Anisotropic uniaxial pressure response of the Mott insulator Ca2RuO4

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    We have investigated the in-plane uniaxial pressure effect on the antiferromagnetic Mott insulator Ca2RuO4 from resistivity and magnetization measurements. We succeeded in inducing the ferromagnetic metallic phase at lower critical pressure than by hydrostatic pressure, indicating that the flattening distortion of the RuO6 octahedra is more easily released under in-plane uniaxial pressure. We also found a striking in-plane anisotropy in the pressure responses of various magnetic phases: Although the magnetization increases monotonically with pressure diagonal to the orthorhombic principal axes, the magnetization exhibits peculiar dependence on pressure along the in-plane orthorhombic principal axes. This peculiar dependence can be explained by a qualitative difference between the uniaxial pressure effects along the orthorhombic a and b axes, as well as by the presence of twin domain structures.Comment: Accepted for publication in Phys. Rev.

    Suppression of both superconductivity and structural transition in hole-doped MoTe2_2 induced by Ta substitution

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    Type-II Weyl semimetal MoTe2_2 exhibits a first-order structural transition at TsT_s \sim250~K and superconducts at TcT_c \sim0.1~K at ambient pressure. Both TsT_s and TcT_c can be manipulated by several tuning parameters, such as hydrostatic pressure and chemical substitution. It is often reported that suppressing TsT_s enhances TcT_c, but our study shows a different behaviour when MoTe2_2 is hole-doped by Ta. When TsT_s is suppressed by Ta doping, TcT_c is also suppressed. Our findings suggest that the suppression of TsT_s does not necessarily enhance superconductivity in MoTe2_2. By connecting with the findings of electron-doped MoTe2_2, we argue that varying electron carrier concentration can effectively tune TcT_c. In addition, the Hall coefficient is enhanced around the doping region, where TsT_s is completely suppressed, suggesting that the critical scattering around the structural transition may also play a role in suppressing TcT_c

    Strong Coupling Superconductivity in the Vicinity of the Structural Quantum Critical Point in (CaxSr1-x)3Rh4Sn13

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    The family of the superconducting quasiskutterudites (CaxSr1?x)3Rh4Sn13 features a structural quantum critical point at xc=0.9, around which a dome-shaped variation of the superconducting transition temperature Tc is found. Using specific heat, we probe the normal and the superconducting states of the entire series straddling the quantum critical point. Our analysis indicates a significant lowering of the effective Debye temperature on approaching xc, which we interpret as a result of phonon softening accompanying the structural instability. Furthermore, a remarkably large enhancement of 2?/kBTc and ?C/?Tc beyond the Bardeen-Cooper-Schrieffer values is found in the vicinity of the structural quantum critical point. The phase diagram of (CaxSr1?x)3Rh4Sn13 thus provides a model system to study the interplay between structural quantum criticality and strong electron-phonon coupling superconductivity

    Fermi Surface Reconstruction in CeRh1x_{1-x}Cox_{x}In5_{5}

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    The evolution of the Fermi surface of CeRh1x_{1-x}Cox_xIn5_5 was studied as a function of Co concentration xx via measurements of the de Haas-van Alphen effect. By measuring the angular dependence of quantum oscillation frequencies, we identify a Fermi surface sheet with ff-electron character which undergoes an abrupt change in topology as xx is varied. Surprisingly, this reconstruction does not occur at the quantum critical concentration xcx_c, where antiferromagnetism is suppressed to T=0. Instead we establish that this sudden change occurs well below xcx_c, at the concentration x ~ 0.4 where long range magnetic order alters its character and superconductivity appears. Across all concentrations, the cyclotron effective mass of this sheet does not diverge, suggesting that critical behavior is not exhibited equally on all parts of the Fermi surface.Comment: 4 pages, 4 figure
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