arXiv subjects

Fay Borhani

Publications and source records attributed to Fay Borhani.

3 recordsLinked to original sources

arXiv2026

Chiral spin liquid instability of the Kitaev honeycomb model with crystallographic defects

We study the spin-1/2 Kitaev honeycomb gapless spin liquid in the presence of Stone-Wales-type local lattice defects with odd-sided plaquettes. While the clean Kitaev model has no finite-temperature phase transitions, we find that introducing a finite defect density $n_d\approx 10^{-4}$--$10^{-2}$ produces a true phase transition with a sizeable $T_c \approx 2 n_d$ in units of the Kitaev exchange. The resulting non-Abelian chiral quantum spin liquid exhibits scalar spin chirality and electron orbital magnetization which peak near lattice defects. This disorder-driven instability relies on an emergent long range ferromagnetic interaction $r^{-γ}$ ($γ\approx 2.7$) between defect chiralities, mediated by the nearly-gapless fermions, with implications for topology generation in Dirac cones with fluctuating mass terms.

cond-mat.str-el↗

arXiv2026

Generation of chirality and orbital magnetization by Stone-Wales-type lattice defects in the Kitaev spin liquid

In this work we extend our study of the effect of certain crystallographic defects on the spin-1/2 Kitaev honeycomb spin liquid (arXiv:2511.19409), focusing on its gapless phase and contrasting with the gapped phase. We identify a Stone-Wales (SW) local defect consisting of a 90$^\circ$ bond rotation that preserves Kitaev bond labels for edge-sharing octahedra and thereby enables exact solvability. These SW-type defects involve odd-sided plaquettes with $\pm π/2$ fluxes, but can be created locally. An isolated defect hosts a time-reversal pair of ground-state flux configurations with large net chirality. Certain excitations are also chiral. The chirality manifests in Majorana local Chern marker and in scalar spin chirality, producing electronic orbital magnetization. T-matrix analysis and numerics at finite defect density $n_d$ show that defect chiralities generate a topological gap of $11 n_d$ protecting a Chern number $C=\pm 1$. Emergent ferromagnetic long range Ising interactions $r^{-γ}$ with $2<γ< 3$ between defect chiralities lead to a finite temperature $T_c$ phase transition into the chiral spin liquid. The $T_c$ is proportional to $n_d$ and diverges when $γ\rightarrow 2$. We also consider additional solvable impurity potentials and find that $γ$ can be reduced to below $2.3$ and correspondingly enhance $T_c$. Our results offer applications to 2D Dirac cone systems with a finite density of fluctuating Ising magnetic impurities and to identifying spin liquids with lattice defects.

cond-mat.str-el↗

arXiv2025

Real-space chirality from crystalline topological defects in the Kitaev spin liquid

We show that certain crystalline topological defects in the gapless Kitaev honeycomb spin liquid model generate a chirality and Majorana fermion orbital magnetization that depends in a universal manner on their emergent flux. Focusing on 5-7 dislocations as building blocks, consisting of pentagon and heptagon disclinations, we identify the Kitaev bond label configurations that preserve solvability. By computing two formulations of local markers $M(r)$ we find that the 5 and 7 lattice defects generate a real-space contribution to Chern number and an associated Majorana fermion orbital magnetization proportional to $M(r)$. The sign of the $M(r)$ contribution from each 5/7 defect, i.e. its $q_M=\pm 1$ chirality, is determined by the defect Frank angle sign $F$ and emergent gauge field flux $W = \pm i$ through the expression $q_M = - i F W$. Remarkably, though lattice curvature and torsion can interplay with the surrounding gapless background to modify the profile of $M(r)$, its sign $q_M$ is determined locally, implying that crystalline defects in the Kitaev spin liquid can generate a robust and observable chirality.

cond-mat.str-el↗