arXiv subjects

A. P. Mackenzie

Publications and source records attributed to A. P. Mackenzie.

79 records · Page 5Linked to original sources

arXiv2000

Metamagnetism and critical fluctuations in high quality single crystals of the bilayer ruthenate Sr3Ru2O7

We report the results of low temperature transport, specific heat and magnetisation measurements on high quality single crystals of the bilayer perovskite Sr3Ru2O7, which is a close relative of the unconventional superconductor Sr2RuO4. Metamagnetism is observed, and transport and thermodynamic evidence for associated critical fluctuations is presented. These relatively unusual fluctuations might be pictured as variations in the Fermi surface topography itself. No equivalent behaviour has been observed in the metallic state of Sr2RuO4.

cond-mat.str-el↗

arXiv2000

A reconstruction from small-angle neutron scattering measurements of the real space magnetic field distribution in the mixed state of Sr$_2$RuO$_4$

We have measured the diffracted neutron scattering intensities from the square magnetic flux lattice in the perovskite superconductor Sr$_2$RuO$_4$, which is thought to exhibit p-wave pairing with a two-component order parameter. The relative intensities of different Bragg reflections over a wide range of field and temperature have been shown to be inconsistent with a single component Ginzburg-Landau theory but qualitatively agree with a two component p-wave Ginzburg-Landau theory.

cond-mat.supr-con↗

arXiv2000

Vortex lattice structures and pairing symmetry in Sr2RuO4

Recent experimental results indicate that superconductivity in Sr2RuO4 is described by the p-wave E_u representation of the D_{4h} point group. Results on the vortex lattice structures for this representation are presented. The theoretical results are compared with experiment.

cond-mat.supr-con↗

arXiv1999

Detailed Topography of the Fermi Surface of Sr2RuO4

We apply a novel analysis of the field and angle dependence of the quantum-oscillatory amplitudes in the unconventional superconductor Sr2RuO4 to map its Fermi surface in unprecedented detail, and to obtain previously inaccessible information on the band dispersion. The three quasi-2D Fermi surface sheets not only exhibit very diverse magnitudes of warping, but also entirely different dominant warping symmetries. We use the data to reassess recent results on c-axis transport phenomena.

cond-mat.str-el↗

arXiv1998

Quantum Oscillations and Overcritical Torque Interaction in Sr2RuO4

Sr2RuO4 is the only known layered perovskite oxide superconductor without copper; there is strong evidence for an unconventional ("p-wave") pairing mechanism, and it has recently been shown to possess a cylindrical, "quasi-two-dimensional" Fermi surface. Using Sr2RuO4 as a test case for the detection of quantum oscillations with piezoresistive microcantilevers, the piezolever torque magnetometry technique was successfully implemented on a dilution refrigerator. It was possible to reproduce the quantum-oscillatory magnetization data on all three Fermi surface sheets, in a crystal of microgram mass. Moreover, an absolute estimate of the amplitude of the oscillation is provided. We also investigated the phenomenon of torque interaction which distorts the magnetization signal and introduces harmonics and sidebands to the dHvA spectrum. As the torque interaction effect grows in strength, overcriticality is shown to lead to discrete magnetization jumps and to a near-asymptotically damped "sproing" effect.

cond-mat.str-el↗

arXiv1998

Superconducting Magnetization above the Irreversibility Line in Tl2Ba2CuO6

Piezolever torque magnetometry has been used to measure the magnetization of superconducting Tl2Ba2CuO6. Three crystals with different levels of oxygen overdoping were investigated in magnetic fields up to 10 Tesla. In all cases, the magnetization above the irreversibility line was found to depart from the behaviour M ~ ln(Hc2/H) of a simple London-like vortex liquid. In particular, for a strongly overdoped (Tc = 15K) crystal, the remnant superconducting order above the irreversibility line is characterized by a linear diamagnetic response (M ~ H) that persists well above Tc and also up to the highest field employed.

cond-mat.supr-con↗

arXiv1997

High field study of normal state magneto-transport in the thallium cuprate Tl-2201

We present a study of in-plane normal state magneto-transport in single crystal Tl-2201 in 60T pulsed magnetic fields. In optimally doped samples (Tc ~ 80K) the weak-magnetic-field regime extends to fields as high as 60T, but in overdoped samples (Tc ~ 30K) we are able to leave the weak field regime, as shown by the behavior of both the magnetoresistance and the Hall resistance. Data from samples of both dopings provide constraints on the class of model necessary to describe normal state transport in the cuprates.

cond-mat.str-el↗