Second-order Dirac superconductors and magnetic field induced Majorana hinge modes

• Main Authors: Ghorashi, Sayed Ali Akbar, Hu, Xiang, Hughes, Taylor L, Rossi, Enrico
• Format: Journal Article
• Language: English
• Published: 10-08-2019
• Subjects: Physics - Mesoscale and Nanoscale Physics; Physics - Strongly Correlated Electrons; Physics - Superconductivity
• DOI: 10.48550/arxiv.1901.07579

Phys. Rev. B 100, 020509 (2019) We identify three-dimensional higher-order superconductors characterized by
the coexistence of one-dimensional Majorana hinge states and gapless surface
sates. We show how such superconductors can be obtained starting from the model
of a spinful quadrupolar semimetal with two orbitals and adding an s-wave
superconducting pairing term. By considering all the possible s-wave pairings
satisfying Fermi-Dirac statistics we obtain six different superconducting
models. We find that for two of these models a flat-band of hinge Majorana
states coexist with surface states, and that these models have a non-vanishing
quadrupole-like topological invariant. Two of the other models, in the presence
of a Zeeman term, exhibit helical and dispersive hinge states localized only at
two of the four hinges. We find that these states are protected by combinations
of rotation and mirror symmetries, and that the pair of corners exhibiting
hinge states switches upon changing the sign of the Zeeman term. Furthermore,
we show that these states can be localized to a single hinge with suitable
perturbations. The remaining two models retain gapless bulk and surface states
that spectroscopically obscure any possible hinge states.