618 research outputs found
Two-dimensional superconductivity at a Mott-Insulator/Band-Insulator interface: LaTiO3/SrTiO3
Transition metal oxides display a great variety of quantum electronic
behaviours where correlations often play an important role. The achievement of
high quality epitaxial interfaces involving such materials gives a unique
opportunity to engineer artificial structures where new electronic orders take
place. One of the most striking result in this area is the recent observation
of a two-dimensional electron gas at the interface between a strongly
correlated Mott insulator LaTiO3 and a band insulator SrTiO3. The mechanism
responsible for such a behaviour is still under debate. In particular, the
influence of the nature of the insulator has to be clarified. Here we show that
despite the expected electronic correlations, LaTiO3/SrTiO3 heterostructures
undergo a superconducting transition at a critical temperature Tc=300 mK. We
have found that the superconducting electron gas is confined over a typical
thickness of 12 nm. We discuss the electronic properties of this system and
review the possible scenarios
Magnetically ordered state at correlated oxide interfaces: the role of random oxygen defects
Using an effective one-band Hubbard model with disorder, we consider magnetic
states of the correlated oxide interfaces, where effective hole self-doping and
a magnetially ordered state emerge due to electronic and ionic reconstructions.
By employing the coherent potential approximation, we analyze the effect of
random oxygen vacancies on the two-dimensional magnetism. We find that the
random vacancies enhance the ferromagnetically ordered state and stabilize a
robust magnetization above a critical vacancy concentration of about c=0.1. In
the strong-correlated regime, we also obtain a nonmonotonic increase of the
magnetization upon an increase of vacancy concentration and a substantial
increase of the magnetic moments, which can be realized at oxygen reduced
high-Tc cuprate interfaces.Comment: 8 pages, 2 figures, submitted to J Supercond Novel Magnetism (ICSM12
conference contribution
Systematic Control of Carrier Doping without Disorder at Interface of Oxide Heterostructures
We propose a method to systematically control carrier densities at the
interface of transition-metal oxide heterostructures without introducing
disorders. By inserting non-polar layers sandwiched by polar layers, continuous
carrier doping into the interface can be realized. This method enables us to
control the total carrier densities per unit cell systematically up to high
values of the order unity.Comment: 8 pages, 9 figure
Oxide Heterostructures from a Realistic Many-Body Perspective
Oxide heterostructures are a new class of materials by design, that open the
possibility for engineering challenging electronic properties, in particular
correlation effects beyond an effective single-particle description. This short
review tries to highlight some of the demanding aspects and questions,
motivated by the goal to describe the encountered physics from first
principles. The state-of-the-art methodology to approach realistic many-body
effects in strongly correlated oxides, the combination of density functional
theory with dynamical mean-field theory, will be briefly introduced. Discussed
examples deal with prominent Mott-band- and band-band-insulating type of oxide
heterostructures, where different electronic characteristics may be stabilized
within a single architectured oxide material.Comment: 19 pages, 9 figure
Tuning of metal-insulator transition of two-dimensional electrons at parylene/SrTiO interface by electric field
Electrostatic carrier doping using a field-effect-transistor structure is an
intriguing approach to explore electronic phases by critical control of carrier
concentration. We demonstrate the reversible control of the insulator-metal
transition (IMT) in a two dimensional (2D) electron gas at the interface of
insulating SrTiO single crystals. Superconductivity was observed in a
limited number of devices doped far beyond the IMT, which may imply the
presence of 2D metal-superconductor transition. This realization of a
two-dimensional metallic state on the most widely-used perovskite oxide is the
best manifestation of the potential of oxide electronics
Coexistence of Magnetic Order and Two-dimensional Superconductivity at LaAlO/SrTiO Interfaces
A two dimensional electronic system with novel electronic properties forms at
the interface between the insulators LaAlO and SrTiO. Samples
fabricated until now have been found to be either magnetic or superconducting,
depending on growth conditions. We combine transport measurements with
high-resolution magnetic torque magnetometry and report here evidence of
magnetic ordering of the two-dimensional electron liquid at the interface. The
magnetic ordering exists from well below the superconducting transition to up
to 200 K, and is characterized by an in-plane magnetic moment. Our results
suggest that there is either phase separation or coexistence between magnetic
and superconducting states. The coexistence scenario would point to an
unconventional superconducting phase in the ground state.Comment: 10 pages, 4 figure
Excitations and spin correlations near the interface of two three-dimensional Heisenberg antiferromagnets
Magnetic excitations and spin correlations near the interface of two
spin- Heisenberg antiferromagnets are considered using the spin-wave
approximation. When the interaction between boundary spins differs essentially
from exchange constants inside the antiferromagnets, quasi-two-dimensional spin
waves appear in the near-boundary region. They eject bulk magnons from this
region, thereby dividing the antiferromagnets into areas with different
magnetic excitations. The decreased dimensionality of the near-boundary modes
leads to amplified nearest-neighbor spin correlations in the interface area.Comment: 6 pages, 5 figure
Disturbed Ca2+ Homeostasis in the Gerbil Hippocampus Following Brief Transient Ischemia
開始ページ、終了ページ: 冊子体のページ付
Role of multiple subband renormalization in the electronic transport of correlated oxide superlattices
Metallic behavior of band-insulator/ Mott-insulator interfaces was observed
in artificial perovskite superlattices such as in nanoscale SrTiO3/LaTiO3
multilayers. Applying a semiclassical perspective to the parallel electronic
transport we identify two major ingredients relevant for such systems: i) the
quantum confinement of the conduction electrons (superlattice modulation) leads
to a complex, quasi-two dimensional subband structure with both hole- and
electron-like Fermi surfaces. ii) strong electron-electron interaction requires
a substantial renormalization of the quasi-particle dispersion. We characterize
this renormalization by two sets of parameters, namely, the quasi-particle
weight and the induced particle-hole asymmetry of each partially filled
subband. In our study, the quasi-particle dispersion is calculated
self-consistently as function of microscopic parameters using the slave-boson
mean-field approximation introduced by Kotliar and Ruckenstein. We discuss the
consequences of strong local correlations on the normal-state free-carrier
response in the optical conductivity and on the thermoelectric effects.Comment: 11 pages, 4 figure
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