15 research outputs found
Temperature-Dependent Electron-Electron Interaction in Graphene on SrTiO3
The electron band structure of graphene on SrTiO3 substrate has been
investigated as a function of temperature. The high-resolution angle-resolved
photoemission study reveals that the spectral width at Fermi energy and the
Fermi velocity of graphene on SrTiO3 are comparable to those of graphene on a
BN substrate. Near the charge neutrality, the energy-momentum dispersion of
graphene exhibits a strong deviation from the well-known linearity, which is
magnified as temperature decreases. Such modification resembles the
characteristics of enhanced electron-electron interaction. Our results not only
suggest that SrTiO3 can be a plausible candidate as a substrate material for
applications in graphene-based electronics, but also provide a possible route
towards the realization of a new type of strongly correlated electron phases in
the prototypical two-dimensional system via the manipulation of temperature and
a proper choice of dielectric substrates.Comment: 16 pages, 3 figure
Probing Inhomogeneous Cuprate Superconductivity by Terahertz Josephson Echo Spectroscopy
Inhomogeneities play a crucial role in determining the properties of quantum
materials. Yet methods that can measure these inhomogeneities are few, and
apply to only a fraction of the relevant microscopic phenomena. For example,
the electronic properties of cuprate materials are known to be inhomogeneous
over nanometer length scales, although questions remain about how such disorder
influences supercurrents and their dynamics. Here, two-dimensional terahertz
spectroscopy is used to study interlayer superconducting tunneling in
near-optimally-doped La1.83Sr0.17CuO4. We isolate a 2 THz Josephson echo signal
with which we disentangle intrinsic lifetime broadening from extrinsic
inhomogeneous broadening. We find that the Josephson plasmons are only weakly
inhomogeneously broadened, with an inhomogeneous linewidth that is three times
smaller than their intrinsic lifetime broadening. This extrinsic broadening
remains constant up to 0.7Tc, above which it is overcome by the
thermally-increased lifetime broadening. Crucially, the effects of disorder on
the Josephson plasma resonance are nearly two orders of magnitude smaller than
the in-plane variations in the superconducting gap in this compound, which have
been previously documented using Scanning Tunnelling Microscopy (STM)
measurements. Hence, even in the presence of significant disorder in the
superfluid density, the finite frequency interlayer charge fluctuations exhibit
dramatically reduced inhomogeneous broadening. We present a model that relates
disorder in the superfluid density to the observed lifetimes
Research Update: Orbital polarization in LaNiO3-based heterostructures
The relative energies and occupancies of valence orbital states can dramatically influence collective electronic and magnetic phenomena in correlated transition metal oxide systems. We review the current state of research on the modification and control of these orbital properties in rare-earth nickelates, especially LaNiO3, a model degenerate d orbital system where significant recent progress has been made. Theoretical and experimental results on thin films and heterostructures are described, including the influence of electronic correlation effects. We highlight the latest approaches to achieving non-degenerate bands and discuss the outlook and applicability of this body of knowledge to other correlated metal oxide systems
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Temperature-Dependent Electron-Electron Interaction in Graphene on SrTiO3.
The electron band structure of graphene on SrTiO3 substrate has been investigated as a function of temperature. The high-resolution angle-resolved photoemission study reveals that the spectral width at Fermi energy and the Fermi velocity of graphene on SrTiO3 are comparable to those of graphene on a BN substrate. Near the charge neutrality, the energy-momentum dispersion of graphene exhibits a strong deviation from the well-known linearity, which is magnified as temperature decreases. Such modification resembles the characteristics of enhanced electron-electron interaction. Our results not only suggest that SrTiO3 can be a plausible candidate as a substrate material for applications in graphene-based electronics but also provide a possible route toward the realization of a new type of strongly correlated electron phases in the prototypical two-dimensional system via the manipulation of temperature and a proper choice of dielectric substrates
Synthesis of SnTe Nanoplates with {100} and {111} Surfaces
SnTe is a topological crystalline
insulator that possesses spin-polarized,
Dirac-dispersive surface states protected by crystal symmetry. Multiple
surface states exist on the {100}, {110}, and {111} surfaces of SnTe,
with the band structure of surface states depending on the mirror
symmetry of a particular surface. Thus, to access surface states selectively,
it is critical to control the morphology of SnTe such that only desired
crystallographic surfaces are present. Here, we grow SnTe nanostructures
using vapor–liquid–solid and vapor–solid growth
mechanisms. Previously, SnTe nanowires and nanocrystals have been
grown [Saghir et al. <i>Cryst. Growth Des.</i> <b>2014</b>, <i>14</i>, 2009–2013; Safdar et al. <i>Cryst.
Growth Des.</i> <b>2014</b>, <i>14</i>, 2502–2509;
Safdar et al. <i>Nano Lett.</i> <b>2013</b>, <i>13</i>, 5344–5349; Li et al. <i>Nano Lett.</i> <b>2013</b>, <i>13</i>, 5443–5448]. In this
report, we demonstrate the synthesis of SnTe nanoplates with lateral
dimensions spanning tens of micrometers and thicknesses of a few hundred
nanometers. The top and bottom surfaces are either (100) or (111),
maximizing topological surface states on these surfaces. Magnetotransport
on these SnTe nanoplates shows a high bulk carrier density, consistent
with bulk SnTe crystals arising due to defects such as Sn vacancies.
In addition, we observe a structural phase transition in these nanoplates
from the high-temperature rock salt to a low-temperature rhombohedral
structure. For nanoplates with a very high carrier density, we observe
a slight upturn in resistance at low temperatures, indicating electron–electron
interactions
Temperature-Dependent Electron–Electron Interaction in Graphene on SrTiO<sub>3</sub>
The
electron band structure of graphene on SrTiO<sub>3</sub> substrate
has been investigated as a function of temperature. The high-resolution
angle-resolved photoemission study reveals that the spectral width
at Fermi energy and the Fermi velocity of graphene on SrTiO<sub>3</sub> are comparable to those of graphene on a BN substrate. Near the
charge neutrality, the energy-momentum dispersion of graphene exhibits
a strong deviation from the well-known linearity, which is magnified
as temperature decreases. Such modification resembles the characteristics
of enhanced electron–electron interaction. Our results not
only suggest that SrTiO<sub>3</sub> can be a plausible candidate as
a substrate material for applications in graphene-based electronics
but also provide a possible route toward the realization of a new
type of strongly correlated electron phases in the prototypical two-dimensional
system via the manipulation of temperature and a proper choice of
dielectric substrates