-
Symmetry Enforced Fermi Surface Degeneracies Observed in Time-Reversal Symmetry-Breaking Superconductor LaNiGa$_2$
Authors:
Matthew Staab,
Robert Prater,
Sudheer Sreedhar,
Journey Byland,
Eliana Mann,
Davis Zackaria,
Yunshu Shi,
Henry J. Bowman,
Andrew L. Stephens,
Myung-Chul Jung,
Antia S. Botana,
Warren E. Pickett,
Valentin Taufour,
Inna Vishik
Abstract:
LaNiGa$_2$ is superconductor that breaks time-reversal symmetry in the superconducting state without any known nearby magnetism. Recently, single crystals of LaNiGa$_2$ have been synthesized, revealing a nonsymmorphic Cmcm space group. Here, we report measurements of the electronic structure of LaNiGa$_2$ throughout the three-dimensional Brillouin zone (BZ) using angle-resolved photoemission spect…
▽ More
LaNiGa$_2$ is superconductor that breaks time-reversal symmetry in the superconducting state without any known nearby magnetism. Recently, single crystals of LaNiGa$_2$ have been synthesized, revealing a nonsymmorphic Cmcm space group. Here, we report measurements of the electronic structure of LaNiGa$_2$ throughout the three-dimensional Brillouin zone (BZ) using angle-resolved photoemission spectroscopy (ARPES). Our findings show broad consistency with density functional theory (DFT) calculations and provide evidence for degeneracies in the electronic structure that are predicted from the space group. The calculations also predict four Fermi surfaces which cross the purported nodal plane and should therefore form two degenerate pairs. We report evidence for those predicted symmetry enforced degeneracies as well as accidental near degeneracies throughout the BZ. These degeneracies and near-degeneracies may play a role in the pairing mechanism of LaNiGa$_2$. Our results provide insight into the interplay between structure, Fermiology, and superconductivity in unconventional superconductors with nonsymmorphic space group.
△ Less
Submitted 18 December, 2023;
originally announced December 2023.
-
Gap structure of the non-symmorphic superconductor LaNiGa2 probed by muSR
Authors:
Shyam Sundar,
M. Yakovlev,
N. Azari,
M. Abedi,
D. M. Broun,
H. U. Ozdemir,
S. R. Dunsiger,
D. Zackaria,
H. Bowman,
P. Klavins,
Y. Shi,
V. Taufour,
J. E. Sonier
Abstract:
We report muon spin rotation (muSR) measurements of the temperature dependence of the absolute value of the magnetic penetration depth and the magnetic field dependence of the vortex core size in the mixed state of the non-symmorphic superconductor LaNiGa2. The temperature dependence of the normalized superfluid density is shown to be well described by a two-band model with strong interband coupli…
▽ More
We report muon spin rotation (muSR) measurements of the temperature dependence of the absolute value of the magnetic penetration depth and the magnetic field dependence of the vortex core size in the mixed state of the non-symmorphic superconductor LaNiGa2. The temperature dependence of the normalized superfluid density is shown to be well described by a two-band model with strong interband coupling. Consistent with a strong coupling of the superconducting condensates in two different bands, we show that the field dependence of the vortex core size resembles that of a single-band superconductor. Our results lend support to the proposal that LaNiGa2 is a fully-gapped, internally antisymmetric nonunitary spin-triplet superconductor.
△ Less
Submitted 22 April, 2024; v1 submitted 31 October, 2023;
originally announced November 2023.
-
Thermal expansion coefficients of high thermal conducting BAs and BP materials
Authors:
Sheng Li,
Keith M. Taddei,
Xiqu Wang,
Hanlin Wu,
Jörg Neuefeind,
Davis Zackaria,
Xiaoyuan Liu,
Clarina Dela Cruz,
Bing Lv
Abstract:
Recent reported very high thermal conductivities in the cubic boron arsenide (BAs) and boron phosphide (BP) crystals could potentially provide a revolutionary solution in the thermal management of high power density devices. To fully facilitate such application, compatible coefficient of thermal expansion (CTE) between the heat spreader and device substrate, in order to minimize the thermal stress…
▽ More
Recent reported very high thermal conductivities in the cubic boron arsenide (BAs) and boron phosphide (BP) crystals could potentially provide a revolutionary solution in the thermal management of high power density devices. To fully facilitate such application, compatible coefficient of thermal expansion (CTE) between the heat spreader and device substrate, in order to minimize the thermal stress, need to be considered. Here we report our experimental CTE studies of BAs and BP in the temperature range from 100K to 1150K, through a combination of X-ray single crystal diffraction and neutron powder diffraction. We demonstrated the room temperature CTE, 3.6 $\pm$ 0.15 $\times$ 10E-6 /K for BAs and 3.2 $\pm$ 0.2 $\times$ 10E-6 /K for BP, are more compatible with most of the semiconductors including Si and GaAs, in comparison with diamond, and thus could be better candidates for the future heat spreader materials in power electronic devices.
△ Less
Submitted 10 June, 2019;
originally announced June 2019.