1,332 research outputs found
Coexistence of glassy antiferromagnetism and giant magnetoresistance (GMR) in Fe/Cr multilayer structures
Using temperature-dependent magnetoresistance and magnetization measurements
on Fe/Cr multilayers that exhibit pronounced giant magnetoresistance (GMR), we
have found evidence for the presence of a glassy antiferromagnetic (GAF) phase.
This phase reflects the influence of interlayer exchange coupling (IEC) at low
temperature (T < 140K) and is characterized by a field-independent glassy
transition temperature, Tg, together with irreversible behavior having
logarithmic time dependence below a "de Almeida and Thouless" (AT) critical
field line. At room temperature, where the GMR effect is still robust, IEC
plays only a minor role, and it is the random potential variations acting on
the magnetic domains that are responsible for the antiparallel interlayer
domain alignment.Comment: 5 pages, 4 figure
Large modulation of the Shubnikov-de Haas oscillations by the Rashba interaction at the LaAlO/SrTiO interface
We investigate the 2-dimensional Fermi surface of high-mobility
LaAlO/SrTiO interfaces using Shubnikov-de Haas oscillations. Our
analysis of the oscillation pattern underscores the key role played by the
Rashba spin-orbit interaction brought about by the breaking of inversion
symmetry, as well as the dominant contribution of the heavy /
orbitals on electrical transport. We furthermore bring into light the complex
evolution of the oscillations with the carrier density, which is tuned by the
field effect
Safe Compositional Specification of Networking Systems: A Compositional Analysis Approach
We present a type inference algorithm, in the style of compositional analysis, for the language TRAFFIC—a specification language for flow composition applications proposed in [2]—and prove that this algorithm is correct: the typings it infers are principal typings, and the typings agree with syntax-directed type checking on closed flow specifications. This algorithm is capable of verifying partial flow specifications, which is a significant improvement over syntax-directed type checking algorithm presented in [3]. We also show that this algorithm runs efficiently, i.e., in low-degree polynomial time.National Science Foundation (ITR ANI-0205294, ANI-0095988, ANI-9986397, EIA-0202067
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
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
Influence of non-magnetic impurities on hole doped two-leg Cu-O Hubbard ladders
We study the influence of non magnetic impurities on the phase diagram of
doped two-leg Hubbard Cu-O ladders. In the absence of impurities this system
posseses d-wave superconducting states and orbital current states depending on
the doping. A single, strong, scatterer modifies its environment locally and
this effect is assessed using a renormalization group analysis. At high doping,
disorder causes intraband instabilities and at low doping it promotes interband
instabilities. In the former case, we extend the boundary conformal field
theory method, developed in the context of single chains, to handle the ladder
problem, and we find exact closed-form analytical expressions for the
correlation functions. This allows us to compute experimentally measurable
local quantities such as the nuclear magnetic resonance line broadenings and
scanning tunnelling microscope profiles. We also discuss the low doping regime
where Kondo physics is at play, making qualitative predictions about its
nature. Insight into collective effects is also given in the many weak
impurities case, based on an RG approach. In this regime, one sees the
interplay between interactions and disorder. We emphasize the influence of the
O atoms on disorder effects both for the single- and for the many-defect
situations.Comment: accepted to be published in NJP special editio
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
Bimodal Phase Diagram of the Superfluid Density in LaAlO3/SrTiO3 Revealed by an Interfacial Waveguide Resonator
We explore the superconducting phase diagram of the two-dimensional electron
system at the LaAlO3/SrTiO3 interface by monitoring the frequencies of the
cavity modes of a coplanar waveguide resonator fabricated in the interface
itself. We determine the phase diagram of the superconducting transition as a
function of temperature and electrostatic gating, finding that both the
superfluid density and the transition temperature follow a dome shape, but that
the two are not monotonically related. The ground state of this 2DES is
interpreted as a Josephson junction array, where a transition from long- to
short-range order occurs as a function of the electronic doping. The synergy
between correlated oxides and superconducting circuits is revealed to be a
promising route to investigate these exotic compounds, complementary to
standard magneto-transport measurements.Comment: 5 pages, 4 figures and 10 pages of supplementary materia
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