42 research outputs found
Theoretical investigation of the evolution of the topological phase of BiSe under mechanical strain
The topological insulating phase results from inversion of the band gap due
to spin-orbit coupling at an odd number of time-reversal symmetric points. In
BiSe, this inversion occurs at the point. For bulk
BiSe, we have analyzed the effect of arbitrary strain on the
point band gap using Density Functional Theory. By computing the band structure
both with and without spin-orbit interactions, we consider the effects of
strain on the gap via Coulombic interaction and spin-orbit interaction
separately. While compressive strain acts to decrease the Coulombic gap, it
also increases the strength of the spin-orbit interaction, increasing the
inverted gap. Comparison with BiTe supports the conclusion that effects
on both Coulombic and spin-orbit interactions are critical to understanding the
behavior of topological insulators under strain, and we propose that the
topological insulating phase can be effectively manipulated by inducing strain
through chemical substitution
Theoretical Investigation of the Evolution of the Topological Phase of Bi\u3csub\u3e2\u3c/sub\u3eSe\u3csub\u3e3\u3c/sub\u3e under Mechanical Strain
The topological insulating phase results from inversion of the band gap due to spin-orbit coupling at an odd number of time-reversal symmetric points. In Bi2Se3, this inversion occurs at the Γ point. For bulk Bi2Se3, we have analyzed the effect of arbitrary strain on the Γ point band gap using density functional theory. By computing the band structure both with and without spin-orbit interactions, we consider the effects of strain on the gap via Coulombic interaction and spin-orbit interaction separately. While compressive strain acts to decrease the Coulombic gap, it also increases the strength of the spin-orbit interaction, increasing the inverted gap. Comparison with Bi2Te3 supports the conclusion that effects on both Coulombic and spin-orbit interactions are critical to understanding the behavior of topological insulators under strain, and we propose that the topological insulating phase can be effectively manipulated by inducing strain through chemical substitution
Unconventional superconducting pairing in a B20 Kramers Weyl semimetal
Topological superconductors present an ideal platform for exploring
nontrivial superconductivity and realizing Majorana boundary modes in
materials. However, finding a single-phase topological material with nontrivial
superconducting states is a challenge. Here, we predict nontrivial
superconductivity in the pristine chiral metal RhGe with a transition
temperature of 5.8 K. Chiral symmetries in RhGe enforce multifold Weyl fermions
at high-symmetry momentum points and spin-polarized Fermi arc states that span
the whole surface Brillouin zone. These bulk and surface chiral states support
multiple type-II van Hove singularities that enhance superconductivity in RhGe.
Our detailed analysis of superconducting pairing symmetries involving Chiral
Fermi pockets in RhGe, indicates the presence of nontrivial superconducting
pairing. Our study establishes RhGe as a promising candidate material for
hosting mixed-parity pairing and topological superconductivity.Comment: 7 pages, 4 figure
Machine learning enabled experimental design and parameter estimation for ultrafast spin dynamics
Advanced experimental measurements are crucial for driving theoretical
developments and unveiling novel phenomena in condensed matter and material
physics, which often suffer from the scarcity of facility resources and
increasing complexities. To address the limitations, we introduce a methodology
that combines machine learning with Bayesian optimal experimental design
(BOED), exemplified with x-ray photon fluctuation spectroscopy (XPFS)
measurements for spin fluctuations. Our method employs a neural network model
for large-scale spin dynamics simulations for precise distribution and utility
calculations in BOED. The capability of automatic differentiation from the
neural network model is further leveraged for more robust and accurate
parameter estimation. Our numerical benchmarks demonstrate the superior
performance of our method in guiding XPFS experiments, predicting model
parameters, and yielding more informative measurements within limited
experimental time. Although focusing on XPFS and spin fluctuations, our method
can be adapted to other experiments, facilitating more efficient data
collection and accelerating scientific discoveries