arXiv subjects

Kaito Yoda

Publications and source records attributed to Kaito Yoda.

3 recordsLinked to original sources

arXiv2026

Competition between on-site and off-site pairing phases and surface spectra in superconducting wallpaper fermion systems

We theoretically investigate the competition between on-site and off-site pairings in superconducting topological crystalline insulators hosting wallpaper fermions, a class of surface states protected by nonsymmorphic symmetries. In-plane nearest-neighbor pair hopping stabilizes the $\mathrm{A_{1u}}$ phase, while off-site pairing channels yield additional dominant phases with $\mathrm{B_{2u}}$ and $\mathrm{E_u}$ representations. We further show that the $\mathrm{B_{2u}}$ pairing state supports the hybridization between wallpaper-fermion spectra themselves, whereas a representative time-reversal-invariant nematic $\mathrm{E_u}$ state exhibits spectral hybridization between wallpaper fermion and double Majorana Kramers pairs, yielding twisted surface energy spectra. These results demonstrate that the twisted dispersions arising from hybridization phenomena persist in the presence of off-site pairing interactions.

cond-mat.supr-con↗

arXiv2026

Double-twisted surface spectrum from hybridized Majorana Kramers pairs and wallpaper fermions

We theoretically investigate the superconducting surface states of wallpaper fermions, which are surface quasiparticles of topological nonsymmorphic crystalline insulators protected by a wallpaper group $p4g$ symmetry, based on a tight-binding model for the space group $P4/mbm$ (No. 127). A symmetry-based analysis shows that four types of on-site pair potentials are allowed. Using the symmetries of the wallpaper group $p4g$ and the one-dimensional topological invariants, we clarify that for the $\mathrm{A_{1u}}$ representation, wallpaper fermions and two Majorana Kramers pairs coexist, and hybridization between them give rise to a double-twisted surface state and produces four peaks in the surface density of states. We further find that the mirror Chern number vanishes, indicating that our system realizes mirror-helicity-free surface states. This distinguishes superconducting wallpaper fermions from the other superconducting topological (crystalline) insulators, such as $\mathrm{Cu}_x\mathrm{Bi}_2\mathrm{Se}_3$ and $\mathrm{Sn}_{1-x}\mathrm{In}_x\mathrm{Te}$.

cond-mat.supr-con↗

arXiv2026

Superconducting Gap Structures in Wallpaper Fermion Systems

We theoretically investigate the superconducting gap structures in wallpaper fermions, which are surface states of topological nonsymmorphic crystalline insulators, based on a two-dimensional effective model. A symmetry analysis identifies six types of momentum-independent pair potentials. One hosts a point node, two host line nodes, and the remaining three are fully gapped. By classifying the Bogoliubov--de Gennes Hamiltonian in the zero-dimensional symmetry class, we show that the point and line nodes are protected by $\mathbb{Z}_2$ topological invariants. In addition, for the twofold-rotation-odd pair potential, nodes appear on the glide-invariant line and are protected by crystalline symmetries, as clarified by the Mackey--Bradley theorem.

cond-mat.supr-con↗