170 research outputs found
Prediction of Nontrivial Band Topology and Superconductivity in MgPb
The interplay of BCS superconductivity and nontrivial band topology is
expected to give rise to opportunities for creating topological
superconductors, achieved through pairing spin-filtered boundary modes via
superconducting proximity effects. The thus-engineered topological
superconductivity can, for example, facilitate the search for Majorana fermion
quasiparticles in condensed matter systems. Here we report a first-principles
study of MgPb and predict that it should be a superconducting topological
material. The band topology of MgPb is identical to that of the archetypal
quantum spin Hall insulator HgTe, while isostructural and isoelectronic
MgSn is topologically trivial; a trivial to topological transition is
predicted for MgSnPb for x~0.77. We propose that
MgPb-MgSn quantum wells should generate robust spin-filtered edge
currents in analogy to HgTe/CdTe quantum wells. In addition, our calculations
predict that MgPb should become superconducting upon electron doping.
Therefore, MgPb is expected to provide a practical material platform for
studying emergent phenomena arising from the interplay of superconductivity and
band topology.Comment: 5 figure
Two distinct topological phases in the mixed valence compound YbB6 and its differences from SmB6
We discuss the evolution of topological states and their orbital textures in
the mixed valence compounds SmB6 and YbB6 within the framework of the
generalized gradient approximation plus onsite Coulomb interaction (GGA+U)
scheme for a wide range of values of U. In SmB6, the topological Kondo
insulator (TKI) gap is found to be insensitive to the value of U, but in sharp
contrast, Kondo physics in isostructural YbB6 displays a surprising sensitivity
to U. In particular, as U is increased in YbB6, the correlated TKI state in the
weak-coupling regime transforms into a d-p-type topological insulator phase
with a band inversion between Yb-5d and B-2p orbitals in the intermediate
coupling range, without closing the insulating energy gap throughout this
process. Our theoretical predictions related to the TKI and non-TKI phases in
SmB6 and YbB6 are in substantial accord with recent angle-resolved
photoemission spectroscopy (ARPES) experiments.Comment: 6 pages, 4 figures URL:
http://link.aps.org/doi/10.1103/PhysRevB.91.15515
Surface Versus Bulk Dirac States Tuning in a Three-Dimensional Topological Dirac Semimetal
Recently, crystalline-symmetry-protected three-dimensional (3D) bulk Dirac
semimetal phase has been experimentally identified in a stoichiometric
high-mobility compound, Cd3As2. The Dirac state observed in Cd3As2 has been
attributed to originate mostly from the bulk state while calculations show that
the bulk and surface states overlap over the entire Dirac dispersion energy
range. In this study, we unambiguously reveal doping induced evolution of the
ground state of surface and bulk electron dynamics in a 3D Dirac semimetal. We
develop a systematic technique to isolate the surface and bulk states in
Cd3As2, by simultaneously utilizing angle-resolved photoemission spectroscopy
(ARPES) and in-situ surface deposition. Our experimental results provide a
method for tuning the chemical potential as well as to observe surface states
degenerate with bulk states, which will be useful for future applications of 3D
Dirac semimetal.Comment: 5 pages, 4 figure
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