306 research outputs found
Crystal growth and quantum oscillations in the topological chiral semimetal CoSi
We survey the electrical transport properties of the single-crystalline,
topological chiral semimetal CoSi which was grown via different methods.
High-quality CoSi single crystals were found in the growth from tellurium
solution. The sample's high carrier mobility enables us to observe, for the
first time, quantum oscillations (QOs) in its thermoelectrical signals. Our
analysis of QOs reveals two spherical Fermi surfaces around the R point in the
Brillouin zone corner. The extracted Berry phases of these electron orbits are
consistent with the -2 chiral charge as reported in DFT calculations. Detailed
analysis on the QOs reveals that the spin-orbit coupling induced band-splitting
is less than 2 meV near the Fermi level, one order of magnitude smaller than
our DFT calculation result. We also report the phonon-drag induced large Nernst
effect in CoSi at intermediate temperatures
Tunability of the topological nodal-line semimetal phase in ZrSiX-type materials
The discovery of a topological nodal-line (TNL) semimetal phase in ZrSiS has
invigorated the study of other members of this family. Here, we present a
comparative electronic structure study of ZrSiX (where X = S, Se, Te) using
angle-resolved photoemission spectroscopy (ARPES) and first-principles
calculations. Our ARPES studies show that the overall electronic structure of
ZrSiX materials comprises of the diamond-shaped Fermi pocket, the nearly
elliptical-shaped Fermi pocket, and a small electron pocket encircling the zone
center () point, the M point, and the X point of the Brillouin zone,
respectively. We also observe a small Fermi surface pocket along the
M--M direction in ZrSiTe, which is absent in both ZrSiS and ZrSiSe.
Furthermore, our theoretical studies show a transition from nodal-line to
nodeless gapped phase by tuning the chalcogenide from S to Te in these material
systems. Our findings provide direct evidence for the tunability of the TNL
phase in ZrSiX material systems by adjusting the spin-orbit coupling (SOC)
strength via the X anion.Comment: 7 pages, 4 figure
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