10,023 research outputs found
Metal-to-Insulator Crossover in the Low-Temperature Normal State of Bi_{2}Sr_{2-x}La_{x}CuO_{6+\delta}
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
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
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
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
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
nature of the superdeformed band of and the evolution of the molecular structure
The relation between the superdeformed band of and 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 have considerable
amount of the component. Above the superdeformed
band, we have obtained two excited rotational bands which have more prominent
character of the molecular band. These three
rotational bands are regarded as a series of
molecular bands which were predicted by using the unique
- optical potentil. As the excitation energy and principal
quantum number of the relative motion increase, the cluster structure becomes more prominent but at the same time, the band
members are fragmented into several states
Ando, Lavrov, and Segawa Reply
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}
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 FeSi/Si(111) structures with high-quality hetero-interfaces
To develop silicon-based spintronic devices, we have explored high-quality
ferromagnetic FeSi/silicon (Si) structures. Using low-temperature
molecular beam epitaxy at 130 C, we realize epitaxial growth of
ferromagnetic FeSi layers on Si (111) with keeping an abrupt interface,
and the grown FeSi layer has the ordered phase. Measurements of
magnetic and electrical properties for the FeSi/Si(111) yield a magnetic
moment of ~ 3.16 /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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