1,334 research outputs found
Interface-induced magnetism in perovskite quantum wells
We investigate the angular dependence of the magnetoresistance of thin (< 1
nm), metallic SrTiO3 quantum wells epitaxially embedded in insulating,
ferrimagnetic GdTiO3 and insulating, antiferromagnetic SmTiO3, respectively.
The SrTiO3 quantum wells contain a high density of mobile electrons (~7x10^14
cm^-2). We show that the longitudinal and transverse magnetoresistance in the
structures with GdTiO3 are consistent with anisotropic magnetoresistance, and
thus indicative of induced ferromagnetism in the SrTiO3, rather than a
nonequilibrium proximity effect. Comparison with the structures with
antiferromagnetic SmTiO3 shows that the properties of thin SrTiO3 quantum wells
can be tuned to obtain magnetic states that do not exist in the bulk material.Comment: Accepted for publication as a Rapid Communication in Physical Review
Absence of signatures of Weyl orbits in the thickness dependence of quantum transport in cadmium arsenide
In a Weyl orbit, the Fermi arc surface states on opposite surfaces of the
topological semimetal are connected through the bulk Weyl or Dirac nodes.
Having a real-space component, these orbits accumulate a sample-size-dependent
phase. Following recent work on the three-dimensional Dirac semimetal cadmium
arsenide (Cd3As2), we have sought evidence for this thickness-dependent effect
in quantum oscillations and quantum Hall plateaus in (112)-oriented Cd3As2 thin
films grown by molecular beam epitaxy. We compare quantum transport in films of
varying thickness at apparently identical gate-tuned carrier concentrations and
find no clear dependence of the relative phase of the quantum oscillations on
the sample thickness. We show that small variations in carrier densities,
difficult to detect in low-field Hall measurements, lead to shifts in quantum
oscillations that are commensurate with previously reported phase shifts.
Future claims of Weyl orbits based on the thickness dependence of quantum
transport data require additional studies that demonstrate that these competing
effects have been disentangled
Basal-plane growth of cadmium arsenide by molecular beam epitaxy
(001)-oriented thin films of the three-dimensional Dirac semimetal cadmium
arsenide can realize a quantum spin Hall insulator and other kinds of
topological physics, all within the flexible architecture of epitaxial
heterostructures. Here, we report a method for growing (001) cadmium arsenide
films using molecular beam epitaxy. The introduction of a thin indium arsenide
wetting layer improves surface morphology and structural characteristics, as
measured by x-ray diffraction and reflectivity, atomic force microscopy, and
scanning transmission electron microscopy. The electron mobility of 50-nm-thick
films is found to be 9300 cm2/Vs at 2 K, comparable to the highest-quality
films grown in the conventional (112) orientation. This work demonstrates a
simple experimental framework for exploring topological phases that are
predicted to exist in proximity to the three-dimensional Dirac semimetal phase
Toward an artificial Mott insulator: Correlations in confined, high-density electron liquids in SrTiO3
We investigate correlation physics in high-density, two-dimensional electron
liquids that reside in narrow SrTiO3 quantum wells. The quantum wells are
remotely doped via an interfacial polar discontinuity and the three-dimensional
(3D) carrier density is modulated by changing the width of the quantum well. It
is shown that even at 3D densities well below one electron per site,
short-range Coulomb interactions become apparent in transport, and an
insulating state emerges at a critical density. We also discuss the role of
disorder in the insulating state.Comment: Accepted for publication in Physical Review B (Rapid Communication
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