9,987 research outputs found

    Metal-to-Insulator Crossover in the Low-Temperature Normal State of Bi_{2}Sr_{2-x}La_{x}CuO_{6+\delta}

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    We measure the normal-state in-plane resistivity of La-doped Bi-2201 single crystals at low temperatures by suppressing superconductivity with 60-T pulsed magnetic fields. With decreasing hole doping, we observe a crossover from a metallic to insulating behavior in the low-temperature normal state. This crossover is estimated to occur near 1/8 doping, well inside the underdoped regime, and not at optimum doping as reported for other cuprates. The insulating regime is marked by a logarithmic temperature dependence of the resistivity over two decades of temperature, suggesting that a peculiar charge localization is common to the cuprates.Comment: 4 pages, 5 figures, accepted for publication in PR

    Conductance of Disordered Wires with Symplectic Symmetry: Comparison between Odd- and Even-Channel Cases

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    The conductance of disordered wires with symplectic symmetry is studied by numerical simulations on the basis of a tight-binding model on a square lattice consisting of M lattice sites in the transverse direction. If the potential range of scatterers is much larger than the lattice constant, the number N of conducting channels becomes odd (even) when M is odd (even). The average dimensionless conductance g is calculated as a function of system length L. It is shown that when N is odd, the conductance behaves as g --> 1 with increasing L. This indicates the absence of Anderson localization. In the even-channel case, the ordinary localization behavior arises and g decays exponentially with increasing L. It is also shown that the decay of g is much faster in the odd-channel case than in the even-channel case. These numerical results are in qualitative agreement with existing analytic theories.Comment: 4 page

    Zn-doping effect on the magnetotransport properties of Bi_{2}Sr_{2-x}La_{x}CuO_{6+\delta} single crystals

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    We report the magnetotransport properties of Bi_{2}Sr_{2-x}La_{x}Cu_{1-z}Zn_{z}O_{6+\delta} (Zn-doped BSLCO) single crystals with z of up to 2.2%. Besides the typical Zn-doping effects on the in-plane resistivity and the Hall angle, we demonstrate that the nature of the low-temperature normal state in the Zn-doped samples is significantly altered from that in the pristine samples under high magnetic fields. In particular, we observe nearly-isotropic negative magnetoresistance as well as an increase in the Hall coefficient at very low temperatures in non-superconducting Zn-doped samples, which we propose to be caused by the Kondo scattering from the local moments induced by Zn impurities.Comment: 4 pages, 4 figures, final version (one reference added), published in Phys. Rev.

    Conductance and Its Variance of Disordered Wires with Symplectic Symmetry in the Metallic Regime

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    The conductance of disordered wires with symplectic symmetry is studied by a random-matrix approach. It has been shown that the behavior of the conductance in the long-wire limit crucially depends on whether the number of conducting channels is even or odd. We focus on the metallic regime where the wire length is much smaller than the localization length, and calculate the ensemble-averaged conductance and its variance for both the even- and odd-channel cases. We find that the weak-antilocalization correction to the conductance in the odd-channel case is equivalent to that in the even-channel case. Furthermore, we find that the variance dose not depend on whether the number of channels is even or odd. These results indicate that in contrast to the long-wire limit, clear even-odd differences cannot be observed in the metallic regime.Comment: 9pages, accepted for publication in JPS

    Magnetic shape-memory effects in La2-xSrxCuO4 crystals

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    The magnetic field affects the motion of electrons and the orientation of spins in solids, but it is believed to have little impact on the crystal structure. This common perception has been challenged recently by ferromagnetic shape-memory alloys, where the spin-lattice coupling is so strong that crystallographic axes even in a fixed sample are forced to rotate, following the direction of moments. One would, however, least expect any structural change to be induced in antiferromagnets where spins are antiparallel and give no net moment. Here we report on such unexpected magnetic shape-memory effects that take place ironically in one of the best-studied 2D antiferromagnets, La2-xSrxCuO4 (LSCO). We find that lightly-doped LSCO crystals tend to align their b axis along the magnetic field, and if the crystal orientation is fixed, this alignment occurs through the generation and motion of crystallographic twin boundaries. Both resistivity and magnetic susceptibility exhibit curious switching and memory effects induced by the crystal-axes rotation; moreover, clear kinks moving over the crystal surfaces allow one to watch the crystal rearrangement directly with a microscope or even bare eyes.Comment: 3 pages, 4 figures; shortend version of this paper has been published in Nature as a Brief Communicatio

    16O+16O^{16}{\rm O} + ^{16}{\rm O} nature of the superdeformed band of 32S^{32}{\rm S} and the evolution of the molecular structure

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    The relation between the superdeformed band of 32S^{32}{\rm S} and 16O+16O^{16}{\rm O} + ^{16}{\rm O} molecular bands is studied by the deformed-base antisymmetrized molecular dynamics with the Gogny D1S force. It is found that the obtained superdeformed band members of 32S^{32}{\rm S} have considerable amount of the 16O+16O^{16}{\rm O} + ^{16}{\rm O} component. Above the superdeformed band, we have obtained two excited rotational bands which have more prominent character of the 16O+16O^{16}{\rm O} + ^{16}{\rm O} molecular band. These three rotational bands are regarded as a series of 16O+16O^{16}{\rm O} + ^{16}{\rm O} molecular bands which were predicted by using the unique 16O^{16}{\rm O} -16O^{16}{\rm O} optical potentil. As the excitation energy and principal quantum number of the relative motion increase, the 16O+16O^{16}{\rm O} + ^{16}{\rm O} cluster structure becomes more prominent but at the same time, the band members are fragmented into several states

    Ando, Lavrov, and Segawa Reply

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    Authors' Reply to the Comment by Janossy et al. [cond-mat/0005275] on our article, "Magnetoresistance Anomalies in Antiferromagnetic YBa_{2}Cu_{3}O_{6+x}: Fingerprints of Charged Stripes" [cond-mat/9905071, Phys. Rev. Lett. 83, 2813 (1999)].Comment: 1 page, 1 figure, accepted for publication in PR

    Non-Universal Power Law of the "Hall Scattering Rate" in a Single-Layer Cuprate Bi_{2}Sr_{2-x}La_{x}CuO_{6}

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    In-plane resistivity \rho_{ab}, Hall coefficient, and magnetoresistance (MR) are measured in a series of high-quality Bi_{2}Sr_{2-x}La_{x}CuO_{6} crystals with various carrier concentrations, from underdope to overdope. Our crystals show the highest T_c (33 K) and the smallest residual resistivity ever reported for Bi-2201 at optimum doping. It is found that the temperature dependence of the Hall angle obeys a power law T^n with n systematically decreasing with increasing doping, which questions the universality of the Fermi-liquid-like T^2 dependence of the "Hall scattering rate". In particular, the Hall angle of the optimally-doped sample changes as T^{1.7}, not as T^2, while \rho_{ab} shows a good T-linear behavior. The systematics of the MR indicates an increasing role of spin scattering in underdoped samples.Comment: 4 pages, 5 figure

    Epitaxial ferromagnetic Fe3_{3}Si/Si(111) structures with high-quality hetero-interfaces

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    To develop silicon-based spintronic devices, we have explored high-quality ferromagnetic Fe3_{3}Si/silicon (Si) structures. Using low-temperature molecular beam epitaxy at 130 circ^circC, we realize epitaxial growth of ferromagnetic Fe3_{3}Si layers on Si (111) with keeping an abrupt interface, and the grown Fe3_{3}Si layer has the ordered DO3DO_{3} phase. Measurements of magnetic and electrical properties for the Fe3_{3}Si/Si(111) yield a magnetic moment of ~ 3.16 muBmu_{B}/f.u. at room temperature and a rectifying Schottky-diode behavior with the ideality factor of ~ 1.08, respectively.Comment: 3 pages, 3 figure
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