114 research outputs found
Anomalous Circularly Polarized Light Emission induced by the Optical Berry Curvature Dipole
The ability to selectively excite light with fixed handedness is crucial for
circularly polarized light emission. It is commonly believed that the
luminescent material chirality determines the emitted light handedness,
regardless of the light emitting direction. In this work, we propose an
anomalous circular polarized light emission (ACPLE) whose handedness actually
relies on the emission direction and current direction in electroluminescence.
In a solid semiconductor, the ACPLE originates in the band structure topology
characterized by the optical Berry curvature dipole. ACPLE exists in
inversion-symmetry breaking materials including chiral materials. We exemplify
the ACPLE by estimating the high circular polarization ratio in monolayer
WS. In addition, the ACPLE can be further generalized to magnetic
semiconductors in which the optical Berry curvature plays a leading role
instead. Our finding reveals intriguing consequences of band topology in light
emission and promises optoelectric applications.Comment: 7 pages, 4 figure
Synthesis and characterization of cobalt ferrite powdered materials
Ph.DDOCTOR OF PHILOSOPH
Chirality driven topological electronic structure of DNA-like materials
Topological aspects of the geometry of DNA and similar chiral molecules have
received a lot of attention, while the topology of their electronic structure
is less explored. Previous experiments have revealed that DNA can efficiently
filter spin-polarized electrons between metal contacts, a process called
chiral-induced spin-selectivity (CISS). However, the underlying correlation
between chiral structure and electronic spin remains elusive. In this work, we
reveal an orbital texture in the band structure, a topological characteristic
induced by the chirality. We find that this orbital texture enables the chiral
molecule to polarize the quantum orbital. This orbital polarization effect
(OPE) induces spin polarization assisted by the spin-orbit interaction from a
metal contact and leads to magnetorestistance and chiral separation. The
orbital angular momentum of photoelectrons also plays an essential role in
related photoemission experiments. Beyond CISS, we predict that OPE can induce
spin-selective phenomena even in achiral but inversion-breaking materials.Comment: 24 pages, 4 figures, and Supplementary Material
Prediction of triple point fermions in simple half-Heusler topological insulators
We predict the existence of triple point fermions in the band structure of
several half-Heusler topological insulators by calculations and the
Kane model. We find that many half-Heusler compounds exhibit multiple triple
points along four independent axes, through which the doubly degenerate
conduction bands and the nondegenerate valence band cross each other linearly
nearby the Fermi energy. When projected from the bulk to the (111) surface,
most of these triple points are located far away from the surface
point, as distinct from previously reported triple point fermion
candidates. These isolated triple points give rise to Fermi arcs on the
surface, that can be readily detected by photoemission spectroscopy or scanning
tunneling spectroscopy.Comment: 6 pages, 3 figures. The supplementary information is attached in the
latex packag
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