Abstract
Resistivity and specific heat measurements were performed in the low carrier unconventional superconductor URu2Si2 on various samples with very different qualities. The superconducting transition temperature (TSC) and the hidden order transition temperature (THO) of these crystals were evaluated as a function of the residual resistivity ratio (RRR). In high quality single crystals the resistivity does not seem to follow a T2 dependence above TSC, indicating that the Fermi liquid regime is restricted to low temperatures. However, an analysis of the isothermal longitudinal magnetoresistivity points out that the T2 dependence may be "spoiled" by residual inhomogeneous superconducting contribution. We discuss a possible scenario concerning the distribution of TSC related with the fact that the hidden order phase is very sensitive to the pressure inhomogeneity.
Highlights
The rush to elucidate the enigma of the nature of the hidden order (HO) state of URu2Si2 which appears below THO ∼17.5 K in URu2Si21–3)has led to a large variety of macroscopic as well as microscopic experiments.4) no detailed report has been given on the link between crystal growth, characterization of the crystal purity, and their influence on physical properties of URu2Si2
The apparent consensus on the high pressure phase diagram of URu2Si2 is that at low pressure (P ) the ground state is the exotic HO phase but above a critical pressure Px ∼ 0.5 GPa it switches to a conventional antiferromagnetic phase (AF).4–7) it is established that bulk superconductivity is associated with the HO while it is suppressed in the AF state.7, 8) The persistence of a tiny ordered moment below Px or the observation of a superconducting transition in resistivity up to PSC > 2Px emphasizes that the separation between intrinsic and extrinsic phenomena is still not fully solved
In order to determine the influence of sample quality on the bulk transition temperature of SC and HO, we performed specific heat measurements on crystals with different residual resistivity ratio (RRR)= ρ(300 K)/ρ(2 K) values
Summary
The rush to elucidate the enigma of the nature of the hidden order (HO) state of URu2Si2 which appears below THO ∼17.5 K in URu2Si21–3)has led to a large variety of macroscopic as well as microscopic experiments.4) no detailed report has been given on the link between crystal growth, characterization of the crystal purity, and their influence on physical properties of URu2Si2. We find that the physical properties depend on the sample purity (given by the RRR) as well as the position of the crystals with respect to the crystal’s growth direction and its radial distance from the center of the crystals. Due to the high sensitivity to pressure and uniaxial stress
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