Topological Kondo Superconductors

Yung-Yeh Chang¹, Khoe Nguyen^2*, Kuang-Lung Chen², Chung-Hou Chung²

¹Physics Division, National Center for Theoretical Sciences, Hsinchu 30013, Taiwan
²Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan

* Presenter:Khoe Nguyen, email:nvkhoe@nycu.edu.tw

We theoretically propose a topological Kondo superconducting phase in a two-dimensional Kondo
lattice. Due to the odd parity of the localized f-orbitals, the Kondo hybridization between f-electrons
and conduction electrons shows an odd-parity momentum dependent form factor. Consequently, this
effectively features the spin-orbit interaction. This unconventional type of Kondo hybridization gives
rise to an effective ferromagnetic Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction among the localized f-orbitals via perturbation theory, leading to spin-triplet resonating-valence-bond (RVB) pairing
between f-electrons with p±ip-wave gap symmetry. There exists competition and collaboration between
the Kondo hybridization and the ferromagnetic RKKY coupling. Via a static mean-field approach, we
explore the phase diagram of this model. Apart from a Kondo-dominating and a RVB-dominating
phase, we find a Kondo triplet RVB coexisting phase in the intermediate range of the Kondo to RKKY
coupling ratio. This is a superconducting phase with spin-triplet p ± ip-wave pairing gap. We further
show that this co-existing phase is a time-reversal invariant topological superconducting state which
supports helical Majorana at edges. Our results provide an unique example of topological superconductivity arising from Kondo correlations, and are relevant for the possible topological Kondo superconducting state in heavy-fermion compounds.

Keywords: Topological Kondo superconducting phase, RKKY interaction, Spin-triplet p ± ip-wave pairing, Time-reversal invariant topological superconducting state, Helical Majorana