7 research outputs found
Topological Electride Y<sub>2</sub>C
Two-dimensional (2D)
electrides are layered ionic crystals in which
anionic electrons are confined in the interlayer space. Here, we report
a discovery of nontrivial Z2 topology in the electronic
structures of
2D electride Y<sub>2</sub>C. Based on first-principles calculations,
we found a topological Z2 invariant of (1; 111)
for the bulk band
and topologically protected surface states in the surfaces of Y<sub>2</sub>C, signifying its nontrivial electronic topology. We suggest
a spin-resolved angle-resolved photoemission spectroscopy (ARPES)
measurement to detect the unique helical spin texture of the spin-polarized
topological surface state, which will provide characteristic evidence
for the nontrivial electronic topology of Y<sub>2</sub>C. Furthermore,
the coexistence of 2D surface electride states and topological surface
state enables us to explain the outstanding discrepancy between the
recent ARPES experiments and theoretical calculations. Our findings
establish a preliminary link between the electride in chemistry and
the band topology in condensed-matter physics, which are expected
to inspire further interdisciplinary research between these fields
Topological Nodal-Point Superconductivity in Two-Dimensional Ferroelectric Hybrid Perovskites
Two-dimensional (2D) hybrid organic–inorganic
perovskites
(HOIPs) with enhanced stability, high tunability, and strong spin–orbit
coupling have shown great potential in vast applications. Here, we
extend the already rich functionality of 2D HOIPs to a new territory,
realizing topological superconductivity and Majorana modes for fault-tolerant
quantum computation. Especially, we predict that room-temperature
ferroelectric BA2PbCl4 (BA for benzylammonium)
exhibits topological nodal-point superconductivity (NSC) and gapless
Majorana modes on selected edges and ferroelectric domain walls when
proximity-coupled to an s-wave superconductor and an in-plane Zeeman
field, attractive for experimental verification and application. Since
NSC is protected by spatial symmetry of 2D HOIPs, we envision more
exotic topological superconducting states to be found in this class
of materials due to their diverse noncentrosymmetric space groups,
which may open a new avenue in the fields of HOIPs and topological
superconductivity
Mesoporous Pt@Pt-skin Pt<sub>3</sub>Ni core-shell framework nanowire electrocatalyst for efficient oxygen reduction
The design of Pt-based nanoarchitectures with controllable compositions and morphologies is necessary to enhance their electrocatalytic activity. Herein, we report a rational design and synthesis of anisotropic mesoporous Pt@Pt-skin Pt3Ni core-shell framework nanowires for high-efficient electrocatalysis. The catalyst has a uniform core-shell structure with an ultrathin atomic-jagged Pt nanowire core and a mesoporous Pt-skin Pt3Ni framework shell, possessing high electrocatalytic activity, stability and Pt utilisation efficiency. For the oxygen reduction reaction, the anisotropic mesoporous Pt@Pt-skin Pt3Ni core-shell framework nanowires demonstrated exceptional mass and specific activities of 6.69 A/mgpt and 8.42 mA/cm2 (at 0.9 V versus reversible hydrogen electrode), and the catalyst exhibited high stability with negligible activity decay after 50,000 cycles. The mesoporous Pt@Pt-skin Pt3Ni core-shell framework nanowire configuration combines the advantages of three-dimensional open mesopore molecular accessibility and compressive Pt-skin surface strains, which results in more catalytically active sites and weakened chemisorption of oxygenated species, thus boosting its catalytic activity and stability towards electrocatalysis.</p