Electronic and magnetic properties of the ionic Hubbard model on the striped triangular lattice at 3/4 filling

Ionic Hubbard model on a triangular lattice for Na_0.5CoO_2, Rb_0.5CoO_2 and K_0.5CoO_2: Mean-field slave boson theory

We introduce a strongly correlated mean-field theory of the ionic Hubbard model on the triangular lattice with alternating stripes of site energy using Barnes-Coleman slave bosons. We study the paramagnetic phases of this theory at three quarters filling, where it is a model of Na_0.5CoO_2, Rb_0.5CoO_2, and K_0.5CoO_2. This theory has two bands of fermionic quasi-particles: one of which is filled or nearly filled and hence weakly correlated; the other is half-filled or nearly half-filled and hence strongly correlated. Further results depend strongly on the sign of the hopping integral, t. The …

Gapless spin liquid and pair density wave of the Hubbard model on three-leg triangular cylinders

We study the ground state properties of the Hubbard model on three-leg triangular cylinders using large-scale density-matrix renormalization group simulations. At half-filling, we identify an intermediate gapless spin liquid phase between a metallic phase at weak coupling and Mott insulating dimer phase at strong interaction, which has one gapless spin mode and algebraic spin-spin correlations but exponential decay scalar chiral-chiral correlations. Upon light doping the gapless spin liquid, the system exhibits power-law charge-density-wave (CDW) correlations but short-range single-particle, s…

Quasiclassical magnetic order and its loss in a spin-1/2 Heisenberg antiferromagnet on a triangular lattice with competing bonds

We use the coupled cluster method (CCM) to study the zero-temperature ground-state (GS) properties of a spin-1/2 $J_{1}$--$J_{2}$ Heisenberg antiferromagnet on a triangular lattice with competing nearest-neighbor and next-nearest-neighbor exchange couplings $J_{1}>0$ and $J_{2} \equiv κJ_{1}>0$, respectively, in the window $0 \leq κ< 1$. The classical version of the model has a single GS phase transition at $κ^{cl}=$1/8 in this window from a phase with 3-sublattice antiferromagnetic (AFM) 120$^{\circ}$ Néel order for $κ< κ^{cl}$ to an infinitely degenerate family of 4-sublattice AFM Néel phase…

Quantum domain walls induce incommensurate supersolid phase on the anisotropic triangular lattice

We investigate the extended hard-core Bose-Hubbard model on the triangular lattice as a function of spatial anisotropy with respect to both tunneling and nearest-neighbor interaction strength. At half-filling the system can be tuned from decoupled one-dimensional chains to a two-dimensional solid phase with alternating density order by adjusting the anisotropic coupling. At intermediate anisotropy, however, frustration effects dominate and an incommensurate supersolid phase emerges, which is characterized by incommensurate density order as well as an anisotropic superfluid density. We demonstr…

Commensurate lock-in in holographic non-homogeneous lattices

We consider the spontaneous formation of striped structures in a holographic model which possesses explicit translational symmetry breaking, dual to an ionic lattice with spatially modulated chemical potential. We focus on the perturbative study of the marginal modes which drive the transition to a phase exhibiting spontaneous stripes. We study the wave-vectors of the instabilities with largest critical temperature in a wide range of backgrounds characterized by the period and the amplitude of the chemical potential modulation. We report the first holographic observation of the commensurate lo…

Single-site magnetic anisotropy governed by inter-layer cation charge imbalance in triangular-lattice AYbX$_2$

The behavior in magnetic field of a paramagnetic center is characterized by its $g$ tensor. An anisotropic form of the latter implies different kind of response along different crystallographic directions. Here we shed light on the anisotropy of the $g$ tensor of Yb$^{3+}$ 4$f^{13}$ ions in NaYbS$_2$ and NaYbO$_2$, layered triangular-lattice materials suggested to host spin-liquid ground states. Using quantum chemical calculations we show that, even if the ligand-cage trigonal distortions are significant in these compounds, the crucial role in realizing strongly anisotropic, `noncubic' $g$ fac…

$d^4$自旋轨道Mott绝缘体中的涌现横场Ising模型

Emergent transverse-field Ising model in $\boldsymbol{d}^\mathbf{4}$ spin-orbit Mott insulators

针对强自旋轨道耦合$t_{2g}^4$ Mott绝缘体，本文推导有效自旋1/2交换作用，证明其普遍形成具有内禀横场的反铁磁TFIM，并以Ru$^{4+}$和多种二维晶格相图、激发谱加以定量说明。

Remarkable effects of dopant valency $-$ a comparative study of CaBaCo$_{3.96}$Cr$_{0.04}$O$_7$ and CaBaCo$_{3.96}$Ni$_{0.04}$O$_7$

Distinctive effects of dopant valency is discussed using an impurity level 1% doping each of Cr$^{3+}$ and Ni$^{2+}$ in CaBaCo$_4$O$_7$. Through a comparative study of the magnetic and dielectric properties of multiferroic CaBaCo$_{3.96}$Cr$_{0.04}$O$_7$ and CaBaCo$_{3.96}$Ni$_{0.04}$O$_7$, we highlight that Cr doping does not significantly alter the properties in spite of differences in magnetic spin and ionic radius compared to Co$^{3+}$ and Co$^{2+}$ while Ni doping induces spectacular changes. Particularly, a manifold increase of electric polarization change up to 650 ${\rm μ}$C/m$^2$ at 5…

Real-space Obstruction in Quantum Spin Hall Insulators

The recently introduced classification of two-dimensional insulators in terms of topological crystalline invariants has been applied so far to "obstructed" atomic insulators characterized by a mismatch between the centers of the electronic Wannier functions and the ionic positions. We extend this notion to quantum spin Hall insulators in which the ground state cannot be described in terms of time-reversal symmetric localized Wannier functions. A system equivalent to graphene in all its relevant electronic and topological properties except for a real-space obstruction is identified and studied …

Dipolar Magnetic Interactions and A-type Antiferromagnetic Order in the Zintl Phase Insulator EuZn2P2

Zintl phases, containing strongly covalently bonded frameworks with separate ionically bonded ions, have emerged as a critical materials family in which to couple magnetism and strong spin-orbit coupling to drive diverse topological phases of matter. Here we report the single-crystal synthesis, magnetic, thermodynamic, transport, and theoretical properties of the Zintl compound EuZn2P2 that crystallizes in the anti-La2O3 P-3m1 structure, containing triangular layers of Eu2+ ions. In-plane resistivity measurements reveal insulating behavior with an estimated bandgap of Eg=0.11eV. Comparing Eu m…

阻挫费米子梯中的轨道反铁磁流

Orbital antiferromagnetic currents in a frustrated fermionic ladder

本文研究无自旋离子Hubbard链映射的弱耦合三角梯，通过有效场论揭示完全与不完全动力学阻挫下的轨道反铁磁流、Luther-Emery液体及对称性破缺相。

Anomalous Hall conductivity control in Mn$_3$NiN antiperovskite by epitaxial strain along the kagome plane

Antiferromagnetic manganese-based nitride antiperovskites, such as Mn$_3$NiN, hold a triangular frustrated magnetic ordering over their kagome lattice formed by the Mn atoms along the (111)-plane. As such, frustration imposes a non-trivial interplay between the symmetric and asymmetric magnetic interactions, which can only reach equilibrium in a noncollinear magnetic configuration. Consequently, the associated electronic interactions and their possible tuning by external constraints, such as applied epitaxial strain, play a crucial role in defining the microscopic and macroscopic properties of…