57 research outputs found
Growth of Antiperovskite Oxide Ca3SnO Films by Pulsed Laser Deposition
We report the epitaxial growth of Ca3SnO antiperovskite oxide films on
(001)-oriented cubic yttria-stabilized zirconia (YSZ) substrates by using a
conventional pulsed laser deposition (PLD) technique. In this work, a sintered
Ca3SnO pellet is used as the ablation target. X-ray diffraction measurements
demonstrate the (001) growth of Ca3SnO films with the antiperovskite structure
and a cube-on-cube orientation relationship to the YSZ substrate. The
successful synthesis of the antiperovskite phase is further confirmed by x-ray
photoemission spectroscopy. These results strongly suggest that
antiperovskite-oxide films can be directly grown on substrates from the target
material using a PLD technique
金属酸化物の表面電子構造と表面におけるキャリアダイナミクス
学位の種別: 課程博士審査委員会委員 : (主査)東京大学教授 藤森 淳, 東京大学教授 末元 徹, 東京大学准教授 杉野 修, 東京大学准教授 溝川 貴司, 東京大学准教授 和達 大樹University of Tokyo(東京大学
Emergence of quantum critical behavior in metallic quantum-well states of strongly correlated oxides
Controlling quantum critical phenomena in strongly correlated electron
systems, which emerge in the neighborhood of a quantum phase transition, is a
major challenge in modern condensed matter physics. Quantum critical phenomena
are generated from the delicate balance between long-range order and its
quantum fluctuation. So far, the nature of quantum phase transitions has been
investigated by changing a limited number of external parameters such as
pressure and magnetic field. We propose a new approach for investigating
quantum criticality by changing the strength of quantum fluctuation that is
controlled by the dimensional crossover in metallic quantum well (QW)
structures of strongly correlated oxides. With reducing layer thickness to the
critical thickness of metal-insulator transition, crossover from a Fermi liquid
to a non-Fermi liquid has clearly been observed in the metallic QW of SrVO
by \textit{in situ} angle-resolved photoemission spectroscopy. Non-Fermi liquid
behavior with the critical exponent is found to emerge in the
two-dimensional limit of the metallic QW states, indicating that a quantum
critical point exists in the neighborhood of the thickness-dependent Mott
transition. These results suggest that artificial QW structures provide a
unique platform for investigating novel quantum phenomena in strongly
correlated oxides in a controllable fashion.Comment: 6 pages, 3 figure
Natural van der Waals heterostructural single crystals with both magnetic and topological properties
Heterostructures having both magnetism and topology are promising materials
for the realization of exotic topological quantum states while challenging in
synthesis and engineering. Here, we report natural magnetic van der Waals
heterostructures of (MnBi2Te4)m(Bi2Te3)n that exhibit controllable magnetic
properties while maintaining their topological surface states. The interlayer
antiferromagnetic exchange coupling is gradually weakened as the separation of
magnetic layers increases, and an anomalous Hall effect that is well coupled
with magnetization and shows ferromagnetic hysteresis was observed below 5 K.
The obtained homogeneous heterostructure with atomically sharp interface and
intrinsic magnetic properties will be an ideal platform for studying the
quantum anomalous Hall effect, axion insulator states, and the topological
magnetoelectric effect.Comment: 40 pages, 15 figure
Steady shocks around black holes produced by sub-keplerian flows with negative energy
We discuss a special case of formation of axisymmetric shocks in the
accretion flow of ideal gas onto a Schwarzschild black hole: when the total
energy of the flow is negative. The result of our analysis enlarges the
parameter space for which these steady shocks are exhibited in the accretion of
gas rotating around relativistic stellar objects. Since keplerian disks have
negative total energy, we guess that, in this energy range, the production of
the shock phenomenon might be easier than in the case of positive energy. So
our outcome reinforces the view that sub-keplerian flows of matter may
significantly affect the physics of the high energy radiation emission from
black hole candidates. We give a simple procedure to obtain analytically the
position of the shocks. The comparison of the analytical results with the data
of 1D and 2D axisymmetric numerical simulations confirms that the shocks form
and are stable.Comment: 5 pages, 5 figures, accepted by MNRAS on 10 November 200
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