5,984 research outputs found
Weyl semimetal phase in non-centrosymmetric transition metal monophosphides
Based on first principle calculations, we show that a family of nonmagnetic
materials including TaAs, TaP, NbAs and NbP are Weyl semimetal (WSM) without
inversion center. We find twelve pairs of Weyl points in the whole Brillouin
zone (BZ) for each of them. In the absence of spin-orbit coupling (SOC), band
inversions in mirror invariant planes lead to gapless nodal rings in the
energy-momentum dispersion. The strong SOC in these materials then opens full
gaps in the mirror planes, generating nonzero mirror Chern numbers and Weyl
points off the mirror planes. The resulting surface state Fermi arc structures
on both (001) and (100) surfaces are also obtained and show interesting shapes,
pointing to fascinating playgrounds for future experimental studies.Comment: Updated with k.p model analysis and a movie demonstrating
distribution of nodal rings and Weyl points, 19 pages, 4 figures and 1 tabl
Transition-Metal Pentatelluride ZrTe and HfTe: a Paradigm for Large-gap Quantum Spin Hall Insulators
Quantum spin Hall (QSH) insulators, a new class of quantum matters, can
support topologically protected helical edge modes inside bulk insulating gap,
which can lead to dissipationless transport. A major obstacle to reach wide
application of QSH is the lack of suitable QSH compounds, which should be
easily fabricated and has large size of bulk gap. Here we predict that single
layer ZrTe and HfTe are the most promising candidates to reach the
large gap QSH insulators with bulk direct (indirect) band gap as large as 0.4
eV (0.1 eV), and robust against external strains. The 3D crystals of these two
materials are good layered compounds with very weak inter-layer bonding and are
located near the phase boundary between weak and strong topological insulators,
which pave a new way to future experimental studies on both QSH effect and
topological phase transitions.Comment: 16 pages, 6 figure
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