Spontaneous Parity Breaking in Spin-Orbital Coupled Systems

Abstract

Effects of spontaneous parity breaking by charge, spin, and orbital orders are investigated in a two-band Hubbard model on a honeycomb lattice. This is a minimal model in which the inter-orbital hopping, atomic spin-orbit coupling, and strong electron correlation give rise to fascinating properties, such as the magnetoelectric effects, quantum spin Hall effect, and spin or valley splitting in the band structure. We perform the symmetry analysis of possible broken-parity states and the mean-field analysis of their competition. We find that the model at 1/4 filling exhibits a spin-orbital composite ordered state and a charge ordered state, in addition to a paramagnetic quantum spin-Hall insulator. We show that the composite ordered phase exhibits two types of magnetoelectric responses. The charge ordered state shows spin splitting in the band structure, while the topological nature varies depending on electron correlations.

5 pages, 3 figures

References in corpus (5)

• Quantum Spin Hall Effect and Topological Phase Transition in HgTe Quantum Wells
• Flat bands and Wigner crystallization in the honeycomb optical lattice
• Coupling the valley degree of freedom to antiferromagnetic order
• The $p_{x,y}$-orbital counterpart of graphene: cold atoms in the honeycomb optical lattice
• Toroidal order in metals without local inversion symmetry

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• Electric Octupole Order in Bilayer Ruthenate Sr${}_3$Ru${}_2$O${}_7$
• Odd-Parity Multipoles by Staggered Magnetic Dipole and Electric Quadrupole Orderings in CeCoSi
• Electric octupole order in bilayer Rashba system
• Spin-orbital-momentum locking under odd-parity magnetic quadrupole ordering
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• Toroidal order in a partially disordered state on a layered triangular lattice: implication to UNi4B
• Electron Correlation Effects in Non-Centrosymmetric Metals in the Weak Coupling Regime
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• Magnetoelectric Response in Electric Octupole State: Possible Hidden Order in Cuprate Superconductors