82 research outputs found
Low-Thermal-Budget Ferroelectric Field-Effect Transistors Based on CuInP2S6 and InZnO
In this paper, we demonstrate low-thermal-budget ferroelectric field-effect
transistors (FeFETs) based on two-dimensional ferroelectric CuInP2S6 (CIPS) and
oxide semiconductor InZnO (IZO). The CIPS/IZO FeFETs exhibit non-volatile
memory windows of ~1 V, low off-state drain currents, and high carrier
mobilities. The ferroelectric CIPS layer serves a dual purpose by providing
electrostatic doping in IZO and acting as a passivation layer for the IZO
channel. We also investigate the CIPS/IZO FeFETs as artificial synaptic devices
for neural networks. The CIPS/IZO synapse demonstrates a sizeable dynamic ratio
(125) and maintains stable multi-level states. Neural networks based on
CIPS/IZO FeFETs achieve an accuracy rate of over 80% in recognizing MNIST
handwritten digits. These ferroelectric transistors can be vertically stacked
on silicon CMOS with a low thermal budget, offering broad applications in
CMOS+X technologies and energy-efficient 3D neural networks
Electronic and magnetic phase diagrams of Kitaev quantum spin liquid candidate NaCoTeO
The 3 Co-based insulating magnet \NCTO{} has recently been
reported to have strong Kitaev interactions on a honeycomb lattice, and is thus
being considered as a Kitaev quantum spin liquid candidate. However, due to the
existence of other types of interactions, a spontaneous long-range magnetic
order occurs. This order is suppressed by applied magnetic fields leading to a
succession of phases and ultimately saturation of the magnetic moments. The
precise phase diagram, the nature of the phases, and the possibility that one
of the field-induced phases is a Kitaev quantum spin liquid phase are still a
matter of debate. Here we measured an extensive set of physical properties to
build the complete temperature-field phase diagrams to magnetic saturation at
10 T for magnetic fields along the - and -axes, and a partial phase
diagram up to 60 T along . We probe the phases using magnetization, specific
heat, magnetocaloric effect, magnetostriction, dielectric constant, and
electric polarization, which is a symmetry-sensitive probe. With these
measurements we identify all the previously incomplete phase boundaries and
find new high-field phase boundaries. We find strong magnetoelectric coupling
in the dielectric constant and moderate magnetostrictive coupling at several
phase boundaries. Furthermore, we detect the symmetry of the magnetic order
using electrical polarization measurements under magnetic fields. Based on our
analysis, the absence of electric polarization under zero or finite magnetic
field in any of the phases or after...Comment: LA-UR-22-3257
One-ninth magnetization plateau stabilized by spin entanglement in a kagome antiferromagnet
The spin-1/2 antiferromagnetic Heisenberg model on a Kagome lattice is
geometrically frustrated, which is expected to promote the formation of
many-body quantum entangled states. The most sought-after among these is the
quantum spin liquid phase, but magnetic analogs of liquid, solid, and
supersolid phases may also occur, producing fractional plateaus in the
magnetization. Here, we investigate the experimental realization of these
predicted phases in the Kagome material YCu3(OD)6+xBr3-x (x=0.5). By combining
thermodynamic and Raman spectroscopic techniques, we provide evidence for
fractionalized spinon excitations and observe the emergence of a 1/9
magnetization plateau. These observations establish YCu3(OD)6+xBr3-x as a model
material for exploring the 1/9 plateau phase.Comment: to appear in Nature Physics, 33 pagses, 15 figure
Continuous spin excitations in the three-dimensional frustrated magnet K2Ni2(SO4)3
Continuous spin excitations are widely recognized as one of the hallmarks of
novel spin states in quantum magnets, such as quantum spin liquids (QSLs).
Here, we report the observation of such kind of excitations in K2Ni2(SO4)3,
which consists of two sets of intersected spin-1 Ni2+ trillium lattices. Our
inelastic neutron scattering measurement on single crystals clearly shows a
dominant excitation continuum, which exhibits a distinct temperature-dependent
behavior from that of spin waves, and is rooted in strong quantum spin
fluctuations. Further using the self-consistent-gaussian-approximation method,
we determined the fourth- and fifth-nearest neighbor exchange interactions are
dominant. These two bonds together form a unique three-dimensional network of
corner-sharing tetrahedra, which we name as ''hyper-trillium'' lattice. Our
results provide direct evidence for the existence of QSL features in
K2Ni2(SO4)3 and highlight the potential for the hyper-trillium lattice to host
frustrated quantum magnetism.Comment: 6 pages and 5 figures, plus several pages of supplemental material,
comments are welcom
Field-induced spin level crossings within a quasi-XY antiferromagnetic state in BaFeSiO
We present a high-field study of the strongly anisotropic easy-plane square
lattice = 2 quantum magnet BaFeSiO. This compound is a
rare high-spin antiferromagnetic system with very strong easy-plane anisotropy,
such that the interplay between spin level crossings and antiferromagnetic
order can be studied. We observe a magnetic field-induced spin level crossing
occurring within an ordered state. This spin level crossing appears to preserve
the magnetic symmetry while producing a non-monotonic dependence the order
parameter magnitude. The resulting temperature-magnetic field phase diagram
exhibits two dome-shaped regions of magnetic order overlapping around 30 T. The
ground state of the lower-field dome is predominantly a linear combination of
and states, while the ground state
of the higher-field dome can be approximated by a linear combination of and states. At 30 T, where the spin
levels cross, the magnetization exhibits a slanted plateau, {\color {black}the
magnetocaloric effect shows a broad hump, and the electric polarization shows a
weak slope change}. We determined the detailed magnetic phase boundaries and
the spin level crossings using measurements of magnetization, electric
polarization, and the magnetocaloric effect in pulsed magnetic fields to 60 T.
We calculate these properties using a mean field theory based on direct
products of SU(5) coherent states and find good agreement. Finally, we measure
and calculate the magnetically-induced electric polarization that reflects
magnetic ordering and spin level crossings. This multiferroic behavior provides
another avenue for detecting phase boundaries and symmetry changes.Comment: 9 pages, 5 figure
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