• DOI:10.1103/PhysRevB.99.224418
• Corpus ID: 118944571

Ground state and low-energy excitations of the Kitaev-Heisenberg two-leg ladder

@article{Agrapidis2019GroundSA,
  title={Ground state and low-energy excitations of the Kitaev-Heisenberg two-leg ladder},
  author={Cli{\`o} Efthimia Agrapidis and Jeroen van den Brink and Satoshi Nishimoto},
  journal={Physical Review B},
  year={2019}
}

• C. E. Agrapidis, J. Brink, S. Nishimoto
• Published 1 February 2019
• Physics
• Physical Review B

We study the ground state and low-lying excited states of the Kitaev-Heisenberg model on a ladder geometry using the density matrix renormalization group and Lanczos exact diagonalization methods. The Kitaev and Heisenberg interactions are parametrized as $K=\sin\phi$ and $J=\cos\phi$ with an angle parameter $\phi$. Based on the results for several types of order parameters, excitation gaps, and entanglement spectra, the $\phi$-dependent ground-state phase diagram is determined. Remarkably, the phase diagram is quite similar to that of the Kitaev-Heisenberg model on a honeycomb lattice, exhibiting the same long-range ordered states, namely rung-singlet (analog to Neel in 3D), zigzag, ferromagnetic, and stripy; and the presence of Kitaev spin liquids around the exactly solvable Kitaev points $\phi=\pm\pi/2$. We also calculate the expectation value of a plaquette operator corresponding to a $\pi$-flux state in order to establish how the Kitaev spin liquid extends away from the $\phi=\pm\pi/2$. Furthermore, we determine the dynamical spin structure factor and discuss the effect of the Kitaev interaction on the spin-triplet dispersion.