Biomedical subjects

Yoshiteru Maeno

Publications and source records attributed to Yoshiteru Maeno.

7 recordsLinked to original sources

PubMed2006

Dynamical superconducting order parameter domains in Sr2RuO4.

We present direct evidence for complex p-wave order parameter symmetry and the presence of dynamical chiral order parameter domains of the form px +/- ipy in the ruthenate superconductor Sr2RuO4. The domain structure creates differences in the magnetic field modulation of the critical current of Josephson junctions fabricated on orthogonal faces of Sr2RuO4 single crystals. Transitions between the chiral states of a domain or the motion of domain walls separating them generates telegraph noise in the critical current as a function of magnetic field or time and is responsible for hysteresis observed in field sweeps of the critical current. The presence of such domains confirms the p-wave triplet spin and complex (broken time-reversal symmetry) nature of the superconducting pairing state in Sr2RuO4.

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PubMed2006

High resolution polar Kerr effect measurements of Sr2RuO4: evidence for broken time-reversal symmetry in the superconducting state.

The polar Kerr effect in the spin-triplet superconductor Sr2RuO4 was measured with high precision using a Sagnac interferometer with a zero-area Sagnac loop. We observed nonzero Kerr rotations as big as 65 nanorad appearing below Tc in large domains. Our results imply a broken time-reversal symmetry state in the superconducting state of Sr2RuO4, similar to 3He-A.

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PubMed2006

Nearly free electrons in the layered oxide superconductor Ag5Pb2O6.

We present first measurements of quantum oscillations in the layered oxide superconductor Ag5Pb2O6. From a detailed angular and temperature dependent study of the de Haas-van Alphen effect we determine the electronic structure and demonstrate that the electron masses are very light, m* approximately 1.2me. The Fermi surface we observe is essentially that expected of nearly free electrons--establishing Ag5Pb2O6 as the first known example of a monovalent, nearly free electron superconductor at ambient pressure.

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PubMed2005

Field-induced transition on a triangular plane in the spin-ice compound Dy2Ti2O7.

The origin of the lowest-temperature anomaly reported several years ago using a polycrystalline sample of the spin-ice compound Dy2Ti2O7 has remained unresolved. Here we finally clarify its origin by susceptibility measurements down to 65 mK using single crystals under accurate control of the magnetic fields in two independent directions. We demonstrate that the transition is induced under a subtle field combination that precisely cancels the nearest-neighbor spin interactions acting on the spins on the triangular lattice within the pyrochlore structure. Contrary to the other two field-induced transitions, this transition is driven only by the interactions beyond the nearest neighbors. Our observation thus provides the first qualitative evidence for the essential importance of the dipolar interaction beyond the nearest neighbors in the spin ice.

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PubMed2005

Spin disorder on a triangular lattice.

As liquids crystallize into solids on cooling, spins in magnets generally form periodic order. However, three decades ago, it was theoretically proposed that spins on a triangular lattice form a liquidlike disordered state at low temperatures. Whether or not a spin liquid is stabilized by geometrical frustration has remained an active point of inquiry ever since. Our thermodynamic and neutron measurements on NiGa2S4, a rare example of a two-dimensional triangular lattice antiferromagnet, demonstrate that geometrical frustration stabilizes a low-temperature spin-disordered state with coherence beyond the two-spin correlation length. Spin liquid formation may be an origin of such behavior.

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PubMed2004

Unusual oscillation in tunneling magnetoresistance near a quantum critical point in Sr3Ru2O7.

We performed single-electron tunneling measurements on bilayer ruthenate Sr3Ru2O7. We observe an unusual oscillation in tunneling magnetoresistance near the metamagnetic quantum phase transition. The characteristic features of this oscillation suggest that it is unrelated to traditional quantum oscillations caused by orbit quantization. In addition, tunneling spectra are found to change sharply in the low bias voltage range of V<2 mV near the transition field. These observations reveal that the Fermi surface of Sr3Ru2O7 changes in a surprising way as the system undergoes strong critical fluctuations.

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PubMed2002

Non-fermi-liquid behavior in Sr2RuO4 with nonmagnetic impurities.

We report that the quasi-two-dimensional Fermi-liquid behavior of the spin-triplet superconductor Sr2RuO4 breaks down in the vicinity of the critical impurity concentration for the onset of magnetic order induced by nonmagnetic Ti4+ impurities. The non-Fermi-liquid behavior is interpreted in terms of the two-dimensional antiferromagnetic fluctuations, which arise mainly from the nesting within one of the Fermi-surface sheets. We argue against the main role of such magnetic fluctuations in the pairing mechanism.

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