40 research outputs found
Effective electric field: quantifying the sensitivity of searches for new P,T-odd physics with EuCl6HO
Laboratory-scale precision experiments are a promising approach to searching
for physics beyond the standard model. Non-centrosymmetric solids offer
favorable statistical sensitivity for efforts that search for new fields, whose
interactions violate the discrete parity and time-reversal symmetries. One
example is the electric Cosmic Axion Spin Precession Experiment (CASPEr-e),
which is sensitive to the defining interaction of the QCD axion dark matter
with gluons in atomic nuclei. The effective electric field is the parameter
that quantifies the sensitivity of such experiments to new physics. We describe
the theoretical approach to calculating the effective electric field for
non-centrosymmetric sites in ionic insulating solids. We consider the specific
example of the EuCl6HO crystal, which is a particularly promising
material. The optimistic estimate of the effective electric field for the
Eu isotope in this crystal is 10 MV/cm. The calculation uncertainty is
estimated to be two orders of magnitude, dominated by the evaluation of the
Europium nuclear Schiff moment
Magnetic properties of iron pnictides from spin-spiral calculations
The wave-vector (q) and doping dependences of the magnetic energy, iron
moment, and effective exchange interactions in LaFeAsO, BaFe2As2, and SrFe2As2\
are studied by self-consistent LSDA calculations for co-planar spin spirals.
For the undoped compounds, the calculated total energy, E(q), reaches its
minimum at q corresponding to stripe anti-ferromagnetic order. In LaFeAsO, this
minimum becomes flat already at low levels of electron-doping and shifts to an
incommensurate q at delta=0.2, where delta is the number of additional
electrons (delta>0) or holes (delta<0) per Fe. In BaFe2As2 and SrFe2As2, stripe
order remains stable for hole doping down to delta=-0.3. Under electron doping,
on the other hand, the E(q) minimum shifts to incommensurate q already at
delta=0.1.Comment: 4 pages, 2 figures, International Conference on Magnetism, Karlsruhe,
July 26 - 31, 200
Dirac Surface States and Nature of Superconductivity in Noncentrosymmetric BiPd
In non-magnetic bulk materials, inversion symmetry protects the spin
degeneracy. If the bulk crystal structure lacks a centre of inversion, however,
spin-orbit interactions lift the spin degeneracy, leading to a Rashba metal
whose Fermi surfaces exhibit an intricate spin texture. In superconducting
Rashba metals a pairing wavefunction constructed from these complex spin
structures will generally contain both singlet and triplet character. Here we
examine the possible triplet components of the order parameter in
noncentrosymmetric BiPd, combining for the first time in a noncentrosymmetric
superconductor macroscopic characterization, atomic-scale ultra-low-temperature
scanning tunnelling spectroscopy, and relativistic first-principles
calculations. While the superconducting state of BiPd appears topologically
trivial, consistent with Bardeen-Cooper-Schrieffer theory with an order
parameter governed by a single isotropic s-wave gap, we show that the material
exhibits Dirac-cone surface states with a helical spin polarization.Comment: replaced by published versio
Recommended from our members
A Giant Bulk-Type Dresselhaus Splitting with 3D Chiral Spin Texture in IrBiSe
Materials with giant spin splitting are desired for spintronic applications. The fabrications of spintronic devices from half metals with one spin direction are often hampered, however, by stray magnetic fields, domain walls, short spin coherence times, scattering on magnetic atoms or magnetically active interfaces, and other characteristics that come along with the magnetism. The surfaces of topological insulators, or Dirac/Weyl semimetals, could be an alternative, but production of high-quality thin films without the presence of the bulk states at the Fermi energy remains very challenging. Here, by utilizing angle-resolved photoemission spectroscopy, a record-high Dresselhaus spin–orbit splitting of the bulk state in the nonmagnetic IrBiSe is found. The band structure calculations indicate that the splitting band is fully spin-polarized with 3D chiral spin texture. As a source of spin-polarized electrons, lightly doped IrBiSe is expected to generate electric-field-controlled spin-polarized currents, free from back scattering, and could host triplet and Fulde–Ferrel–Larkin–Ovchinnikov (FFLO) superconductivity. © 2020 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinhei
Kinetic stabilization of 1D surface states near twin boundaries in noncentrosymmetric BiPd
CMY, CT and PW acknowledge funding from EPSRC through EP/I031014/1 and EP/L505079/1 and DCP acknowledges support from the National Natural Science Foundation of China (Project No. 11650110428).The search for one-dimensional (1D) topologically-protected electronic states has become an important research goal for condensed matter physics owing to their potential use in spintronic devices or as a building block for topologically non-trivial electronic states. Using low temperature scanning tunneling microscopy, we demonstrate the formation of 1D electronic states at twin boundaries at the surface of the noncentrosymmetric material BiPd. These twin boundaries are topological defects which separate regions with antiparallel orientations of the crystallographic {b} axis. We demonstrate that the formation of the 1D electronic states can be rationalized by a change in effective mass of two-dimensional surface states across the twin boundary. Our work therefore reveals a novel route towards designing 1D electronic states with strong spin-orbit coupling.PostprintPostprintPeer reviewe