From chiral d-wave to nodal line superconductivity in the harmonic honeycomb lattices
2016 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 94, no 10, 104513Article in journal (Refereed) Published
Motivated by the recent realization of the three-dimensional hyperhoneycomb and stripyhoneycomb lattices in lithium iridate (Li2IrO3), we study the possible spin-singlet superconducting states on the whole series of harmonic honeycomb lattices. Beginning with an isolated out-of-plane twist making the honeycomb lattice three-dimensional, we find that the chiral d +/- id' state, well-known from the honeycomb lattice, is realized in the largest members of the series at low to intermediate doping. Along the twist, four chiral edge states form a two-dimensional dispersive band. Reducing the distance between the twists to form the smaller members of the harmonic honeycomb lattices, the degeneracy between the d-wave states is lifted, which finally destroys the chiral state. By analyzing the hyper- and stripyhoneycomb lattices and generalizing using the D-2h point group of all the harmonic honeycomb lattices, we show that the superconducting state often belongs to the trivial irreducible representation. This state has nodal lines at low to intermediate doping, which is possible because the full lattice symmetry allows sign changes between different sets of bonds. We also find time-reversal symmetry broken states, which are either fully gapped or feature nodal points, in certain parts of the phase diagram. Finally, we draw a comparison between the states classified in terms of the D-2h symmetries and those observed on the D-6h honeycomb lattice.
Place, publisher, year, edition, pages
2016. Vol. 94, no 10, 104513
Condensed Matter Physics
IdentifiersURN: urn:nbn:se:uu:diva-305452DOI: 10.1103/PhysRevB.94.104513ISI: 000383339100005OAI: oai:DiVA.org:uu-305452DiVA: diva2:1038667
FunderSwedish Research CouncilSwedish Foundation for Strategic Research Göran Gustafsson Foundation for promotion of scientific research at Uppala University and Royal Institute of Technology