96 research outputs found
Localized Distributions of Quasi Two-Dimensional Electronic States near Defects Artificially Created at Graphite Surfaces in Magnetic Fields
We measured the local density of states of a quasi two-dimensional electron
system (2DES) near defects, artificially created by Ar-ion sputtering, on
surfaces of highly oriented pyrolytic graphite (HOPG) with scanning tunneling
spectroscopy (STS) in high magnetic fields. At valley energies of the Landau
level spectrum, we found two typical localized distributions of the 2DES
depending on the defects. These are new types of distributions which are not
observed in the previous STS work at the HOPG surface near a point defect [Y.
Niimi \textit{et al}., Phys. Rev. Lett. {\bf 97}, 236804 (2006).]. With
increasing energy, we observed gradual transformation from the localized
distributions to the extended ones as expected for the integer quantum Hall
state. We show that the defect potential depth is responsible for the two
localized distributions from comparison with theoretical calculations.Comment: 4 pages, 3 figure
Anomalous Transport through the p-Wave Superconducting Channel in the 3-K Phase of Sr2RuO4
Using micro fabrication techniques, we extracted individual channels of
3-Kelvin (3-K) phase superconductivity in Sr2RuO4-Ru eutectic systems and
confirmed odd-parity superconductivity in the 3-K phase, similar to pure
Sr2RuO4. Unusual hysteresis in the differential resistance-current and
voltage-current characteristics observed below 2 K indicates the internal
degrees of freedom of the superconducting state. A possible origin of the
hysteresis is current-induced chiral-domain-wall motion due to the chiral
p-wave state.Comment: 4 pages, 5 figures, accepted for publication in Phys. Rev. Let
Edge states of SrRuO detected by in-plane tunneling spectroscopy
We perform tunneling spectroscopy of SrRuO searching for the edge
states peculiar to topological superconductivity. Conductance spectra obtained
on SrRuO/Au junctions fabricated using process show broad
humps indicating the successful detection of a-axis edge of 1.5K phase. Three
types of peak shape are detected: domelike peak, split peak and two-step peak.
By comparing the experiments with predictions for unconventional
superconductivity, these varieties are shown to originate from multiband chiral
p-wave symmetry with weak anisotropy of pair amplitude. The broad hump in
conductance spectrum is a direct manifestation of the edge state peculiar to
the chiral p-wave superconductivity.Comment: 7 pages and 4 figure
Rate of Volatilization of a Volatile Constituent from Surface of Glass Melts Containing Lead Oxide
A thermal balance technique has been used to study the kinetics of volatilization of a volatile constituent from the surface of glass melts containing lead oxide for extended periods of time in the temperature range 1100° to 1500°C. Distributions of density and refractive index of the glass after heat-treating at 1200-1300°C were also determined
Volatilization of Volatile Constituent from Lead-glass Melts
The kinetics of volatilization of a volatile constituent from the surface of glass melts containing lead oxide for the temperature range of 1100° to 1500°C have been studied with a thermal balance. From the results obtained, it was concluded that both the evaporation-rate coefficient at the surface of the glass melts and the diffusion coefficient of the volatile constituent in the glass melts are controlling factors of the overall rate of volatilization in the system
Temperature dependence of the impurity-induced resonant state in Zn-doped Bi_2Sr_2CaCu_2O by Scanning Tunneling Spectroscopy
We report on the temperature dependence of the impurity-induced resonant
state in Zn-doped Bi_2Sr_2CaCu_2O by scanning tunneling
spectroscopy at 30 mK < T < 52 K. It is known that a Zn impurity induces a
sharp resonant peak in tunnel spectrum at an energy close to the Fermi level.
We observed that the resonant peak survives up to 52 K. The peak broadens with
increasing temperature, which is explained by the thermal effect. This result
provides information to understand the origin of the resonant peak.Comment: 4 pages, 3 figures, to appear in Phys. Rev.
STS Observations of Landau Levels at Graphite Surfaces
Scanning tunneling spectroscopy measurements were made on surfaces of two
different kinds of graphite samples, Kish graphite and highly oriented
pyrolytic graphite (HOPG), at very low temperatures and in high magnetic
fields. We observed a series of peaks in the tunnel spectra, which grow with
increasing field, both at positive and negative bias voltages. These are
associated with Landau quantization of the quasi two-dimensional electrons and
holes in graphite in magnetic fields perpendicular to the basal plane. Almost
field independent Landau levels fixed near the Fermi energy, which are
characteristic of the graphite crystalline structure, were directly observed
for the first time. Calculations of the local density of states at the graphite
surfaces allow us to identify Kish graphite as bulk graphite and HOPG as
graphite with finite thickness effectively
Real-Space Imaging of Alternate Localization and Extension of Quasi Two-Dimensional Electronic States at Graphite Surfaces in Magnetic Fields
We measured the local density of states (LDOS) of a quasi two-dimensional
(2D) electron system near point defects on a surface of highly oriented
pyrolytic graphite (HOPG) with scanning tunneling microscopy and spectroscopy.
Differential tunnel conductance images taken at very low temperatures and in
high magnetic fields show a clear contrast between localized and extended
spatial distributions of the LDOS at the valley and peak energies of the Landau
level spectrum, respectively. The localized electronic state has a single
circular distribution around the defects with a radius comparable to the
magnetic length. The localized LDOS is in good agreement with a spatial
distribution of a calculated wave function for a single electron in 2D in a
Coulomb potential in magnetic fields.Comment: 4 pages, 4 figure
Construction of a Versatile Ultra-Low Temperature Scanning Tunneling Microscope
We constructed a dilution-refrigerator (DR) based ultra-low temperature
scanning tunneling microscope (ULT-STM) which works at temperatures down to 30
mK, in magnetic fields up to 6 T and in ultrahigh vacuum (UHV). Besides these
extreme operation conditions, this STM has several unique features not
available in other DR based ULT-STMs. One can load STM tips as well as samples
with clean surfaces prepared in a UHV environment to an STM head keeping low
temperature and UHV conditions. After then, the system can be cooled back to
near the base temperature within 3 hours. Due to these capabilities, it has a
variety of applications not only for cleavable materials but also for almost
all conducting materials. The present ULT-STM has also an exceptionally high
stability in the presence of magnetic field and even during field sweep. We
describe details of its design, performance and applications for low
temperature physics.Comment: 6 pages, 9 figures. accepted for publication in Rev. Sci. Instru
Local conductance spectra of itinerant ferromagnetic SrRuO3 through break junction
We have measured the local differential conductance spectra (dI/dV-V) of an itinerant ferromagnet composed of polycrystalline SrRuO3 using the mechanically controllable break junction technique. Below the material's Curie temperature (T-C = 160 K), characteristic peak or dip conductance spectra are observed. The characteristic energy scale is comparable to the exchange spin splitting energy that is based on ferromagnetic band calculations. Both the peak and dip spectral shapes are explained based on the itinerant ferromagnetic characteristics of SrRuO3 in terms of spin-dependent transmission, which is similar to the giant magnetoresistance mechanism. (C) 2016 The Japan Society of Applied PhysicsArticleJAPANESE JOURNAL OF APPLIED PHYSICS. 55(9):93004 (2016)journal articl
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