We discuss the tunneling conductance in a ferromagnet-insulator-triplet superconductor junction. We consider the superconducting order parameters with spin triplet pairing having nodes. The nodal structure of the order parameter has been recently confirmed experimentally in Sr_2RuO_4. In particular, we study how a mid-gap structure of the tunnelling conductance depends on the phase difference of the pairing potential as well as on the orientation of the interface.
We discuss the calculations of the ac Hall conductivity for superconductors with the time reversal symmetry breaking states. In the weak coupling theories these states show vanishing Hall response in one band models, even though one expects otherwise on symmetry grounds. On the other hand, the strong coupling approach based on the anti-de Sitter-conformal field theory correspondence leads to the non-vanishing Hall conductivity. We discuss the possible reasons of the discrepancy. The weak coupling many orbital theory leading to the Hall conductivity with correct temperature dependence is also briefly presented.
Electrical resistance, transversal magnetoresistance and the Hall effect were studied on polycrystalline CaTi_xRu_{1-x}O_3 (x=0, 0.07) samples using a conventional Quantum Design PPMS-9 equipment in the temperature range 2-300 K and magnetic field up to 9 T. Substantial differences were found between the two samples: (i) opposite to the metallic character of CaRuO_3, the substituted sample has insulating-like electrical resistance;(ii) the magnetoresistance of the substituted sample changes the sign from negative to positive values with increasing temperature. The magnetoresistance of CaRuO_3 is negative, the sign reversal is induced by magnetic field and only at temperatures below 15 K, such a behaviour is predicted for clustered systems;(iii) the Hall voltage in pure CaRuO_3 also changes sign from negative to positive values above 35 K. This temperature coincides with the observed magnetic transition temperature, indicating that the magnetic state and the carrier character interrelate.
The influence of Ti substitution on the specific heat of the CaTi_xRu_{1-x}O_3 system at low concentrations x=0, 0.005, and 0.03 was studied in the temperature range of 2-300 K at magnetic fields up to 9 T. Small peak was revealed in the C/T vs. T^2 dependence at around 3 K, which are field sensitive (the electronic specific heat coefficient γlinearly decreases with the increase in magnetic field), and might be connected to some kind of magnetic ordering. The coefficient γis suppressed also by Ti substitution.
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