2019/11/30 by Yun-Peng Huang, Jin-Wei Dong, Panagiotis Kotetes +1 · 10 citations
Materials Science · Physics and Astronomy · #Antiferromagnetism #Brillouin zone #Chern class #Degenerate energy levels #Frustration #Ground state #Hexagonal lattice #Hubbard model #Organic and Molecular Conductors Research #Phase diagram #Rare-earth and actinide compounds #Square lattice #Topological Materials and Phenomena #cond-mat.str-el
paper · pdf · doi:10.1103/physrevb.102.195120
published in Physical review. B./Physical review. B 102(19) (American Physical Society) · 14 pages, 8 figures
openalex created_date 2019/12/05 · openalex publication_date 2020/11/12 · arxiv created 2020/11/17 · arxiv updated 2020/11/18 · openalex updated_date 2026/08/05
We employ the Hartree-Fock approximation to identify the magnetic ground state of the Hubbard model on a frustrated square lattice. We investigate the phase diagram as a function of the Coulomb repulsion's strength U, and the ratio t^\ensuremath'/t between the nearest- and next-nearest-neighbor hoppings t and t^\ensuremath'. At half-filling and for a sufficiently large U, an antiferromagnetic chiral spin density wave order with nonzero spin chirality emerges as the ground state in a wide regime of the phase diagram near t^\ensuremath'/t=1/√(2), where the Fermi surface is well nested for both (\ensuremathπ,\ensuremathπ) and (\ensuremathπ,0)/(0,\ensuremathπ) wave vectors. This triple-Q chiral phase is sandwiched by a single-Q N'eel phase and a double-Q coplanar spin-vortex crystal phase, at smaller and larger t^\ensuremath'/t, respectively. The energy spectrum in the chiral spin density wave phase consists of four pairs of degenerate bands. These give rise to two pairs of Dirac cones with the same chirality at the point (\frac\ensuremathπ2,\frac\ensuremathπ2) of the Brillouin zone. We demonstrate that the application of a diagonal strain induces a dxy-wave next-nearest-neighbor hopping which, in turn, opens gaps in the two Dirac cones with opposite masses. As a result, four pairs of well-separated topologically nontrivial bands emerge, and each pair of those contributes with a Chern number \ifmmode±\else\textpm\fi1. At half-filling, this leads to a zero total Chern number and renders the topologically nontrivial properties observable only in the ac response regime. Instead, we show that at (3)/(4) filling, the triple-Q chiral phase yields a Chern insulator exhibiting the quantum anomalous Hall effect.