436 research outputs found
Growth-induced electron mobility enhancement at the LaAlO/SrTiO interface
We have studied the electronic properties of the 2D electron liquid present
at the LaAlO/SrTiO interface in series of samples prepared at different
growth temperatures. We observe that interfaces fabricated at 650{\deg}C
exhibit the highest low temperature mobility () and the lowest sheet carrier density (). These samples show metallic behavior and
Shubnikov-de Haas oscillations in their magnetoresistance. Samples grown at
higher temperatures (800-900{\deg}C) display carrier densities in the range of
and mobilities of at 4K. Reducing their carrier density by field
effect to lowers their mobilites to
bringing the conductance to the
weak-localization regime
A Short-Range FMCW Radar-Based Approach for Multi-Target Human-Vehicle Detection
In this article, a new microwave-radar-based technique for short-range detection and classification of multiple human and vehicle targets crossing a monitored area is proposed. This approach, which can find applications in both security and infrastructure surveillance, relies upon the processing of the scattered-field data acquired by low-cost off-The-shelf components, i.e., a 24 GHz frequency-modulated continuous wave (FMCW) radar module and a Raspberry Pi mini-PC. The developed method is based on an ad hoc processing chain to accomplish the automatic target recognition (ATR) task, which consists of blocks performing clutter and leakage removal with an infinite impulse response (IIR) filter, clustering with a density-based spatial clustering of applications with noise (DBSCAN) approach, tracking using a Benedict-Bordner - filter, features extraction, and finally classification of targets by means of a -nearest neighbor ( -NN) algorithm. The approach is validated in real experimental scenarios, showing its capabilities in correctly detecting multiple targets belonging to different classes (i.e., pedestrians, cars, motorcycles, and trucks)
Epitaxial growth and thermodynamic stability of SrIrO3/SrTiO3 heterostructures
Obtaining high-quality thin films of 5d transition metal oxides is essential
to explore the exotic semimetallic and topological phases predicted to arise
from the combination of strong electron correlations and spin-orbit coupling.
Here, we show that the transport properties of SrIrO3 thin films, grown by
pulsed laser deposition, can be optimized by considering the effect of
laser-induced modification of the SrIrO3 target surface. We further demonstrate
that bare SrIrO3 thin films are subject to degradation in air and are highly
sensitive to lithographic processing. A crystalline SrTiO3 cap layer deposited
in-situ is effective in preserving the film quality, allowing us to measure
metallic transport behavior in films with thicknesses down to 4 unit cells. In
addition, the SrTiO3 encapsulation enables the fabrication of devices such as
Hall bars without altering the film properties, allowing precise
(magneto)transport measurements on micro- and nanoscale devices.Comment: 5 pages, 3 figure
Band inversion driven by electronic correlations at the (111) LaAlO/SrTiO interface
Quantum confinement at complex oxide interfaces establishes an intricate
hierarchy of the strongly correlated -orbitals which is widely recognized as
a source of emergent physics. The most prominent example is the (001)
LaAlO/SrTiO(LAO/STO) interface, which features a dome-shaped phase
diagram of superconducting critical temperature and spin-orbit coupling (SOC)
as a function of electrostatic doping, arising from a selective occupancy of
orbitals of different character. Here we study (111)-oriented LAO/STO
interfaces - where the three orbitals contribute equally to the
sub-band states caused by confinement - and investigate the impact of this
unique feature on electronic transport. We show that transport occurs through
two sets of electron-like sub-bands, and the carrier density of one of the sets
shows a non-monotonic dependence on the sample conductance. Using tight-binding
modeling, we demonstrate that this behavior stems from a band inversion driven
by on-site Coulomb interactions. The balanced contribution of all
orbitals to electronic transport is shown to result in strong SOC with reduced
electrostatic modulation.Comment: 5 pages, 4 figures, (+ supplemental material
Tunable Rashba spin-orbit interaction at oxide interfaces
The quasi-two-dimensional electron gas found at the LaAlO3/SrTiO3 interface
offers exciting new functionalities, such as tunable superconductivity, and has
been proposed as a new nanoelectronics fabrication platform. Here we lay out a
new example of an electronic property arising from the interfacial breaking of
inversion symmetry, namely a large Rashba spin-orbit interaction, whose
magnitude can be modulated by the application of an external electric field. By
means of magnetotransport experiments we explore the evolution of the
spin-orbit coupling across the phase diagram of the system. We uncover a steep
rise in Rashba interaction occurring around the doping level where a quantum
critical point separates the insulating and superconducting ground states of
the system
Seebeck effect in the conducting LaAlO_{3}/SrTiO_{3} interface
The observation of metallic behavior at the interface between insulating
oxides has triggered worldwide efforts to shed light on the physics of these
systems and clarify some still open issues, among which the dimensional
character of the conducting system. In order to address this issue, we measure
electrical transport (Seebeck effect, Hall effect and conductivity) in
LaAlO_{3}/SrTiO_{3} interfaces and, for comparison, in a doped SrTiO_{3} bulk
single crystal. In these experiments, the carrier concentration is tuned, using
the field effect in a back gate geometry. The combined analysis of all
experimental data at 77 K indicates that the thickness of the conducting layer
is ~7 nm and that the Seebeck effect data are well described by a
two-dimensional (2D) density of states. We find that the back gate voltage is
effective in varying not only the charge density, but also the thickness of the
conducting layer, which is found to change by a factor of ~2, using an electric
field between -4 and +4MV/m at 77K. No enhancement of the Seebeck effect due to
the electronic confinement and no evidence for two-dimensional quantization
steps are observed at the interfaces.Comment: 15 pages, 5 figure
Two-dimensional superconductivity at the (111)LaAlO/SrTiO interface
We report on the discovery and transport study of the superconducting ground
state present at the (111)LaAlO/SrTiO interface. The superconducting
transition is consistent with a Berezinskii-Kosterlitz-Thouless transition and
its 2D nature is further corroborated by the anisotropy of the critical
magnetic field, as calculated by Tinkham. The estimated superconducting layer
thickness and coherence length are 10 nm and 60 nm, respectively. The results
of this work provide a new platform to clarify the microscopic details of
superconductivity at LaAlO/SrTiO interfaces, in particular in what
concerns the link with orbital symmetry.Comment: 4 pages, 4 figure
Superconductivity at the LaAlO3/SrTiO3interface
We report on the structural characterization of LaAlO3/SrTiO3 interfaces and
on their transport properties. LaAlO3 films were prepared using pulsed laser deposition
onto TiO2 terminated (001) SrTiO3 substrates inducing a metallic conduction at the
interface. Resistance and Hall effect measurements reveal a sheet carrier density between
0.4 and 1.2·10 14 electrons/cm 2 at room temperature and mobility of ∼ 300 cm 2 V −1 s −1 at low temperatures. A transition to a superconducting state is observed at a temperature of ∼ 200 mK. The superconducting characteristics display signatures of 2D superconductivity
Two-dimensional quantum oscillations of the conductance at LaAlO3/SrTiO3 interfaces
We report on a study of magnetotransport in LaAlO3/SrTiO3 interfaces
characterized by mobilities of the order of several thousands cm/Vs. We
observe Shubnikov-de Haas oscillations that indicate a two-dimensional
character of the Fermi surface. The frequency of the oscillations signals a
multiple sub-bands occupation in the quantum well or a multiple valley
configuration. From the temperature dependence of the oscillation amplitude we
extract an effective carrier mass \,. An electric field
applied in the back-gate geometry increases the mobility, the carrier density
and the oscillation frequency.Comment: 4 pages, 4 figure
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