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Andrey V. Chubukov - One of the best experts on this subject based on the ideXlab platform.
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enhancement of the london penetration depth in pnictides at the onset of Spin Density Wave order under superconducting dome
Physical Review Letters, 2013Co-Authors: Alex Levchenko, Maxim Vavilov, Maxim Khodas, Andrey V. ChubukovAbstract:Recent measurements of the doping dependence of the London penetration depth λ(x) at low T in clean samples of isovalent BaFe2(As(1-x)P(x))2 at T≪T(c) [Hashimoto et al., Science 336, 1554 (2012)] revealed a peak in λ(x) near optimal doping x=0.3. The observation of the peak at T≪T(c), points to the existence of a quantum critical point beneath the superconducting dome. We associate such a quantum critical point with the onset of a Spin-Density-Wave order and show that the renormalization of λ(x) by critical magnetic fluctuations gives rise to the observed feature. We argue that the case of pnictides is conceptually different from a one-component Galilean invariant Fermi liquid, for which correlation effects do not cause the renormalization of the London penetration depth at T=0.
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superconductivity at the onset of Spin Density Wave order in a metal
Bulletin of the American Physical Society, 2013Co-Authors: Yuxuan Wang, Andrey V. ChubukovAbstract:We revisit the issue of superconductivity at the quantum-critical point (QCP) between a 2D paramagnet and a Spin-Density-Wave metal with ordering momentum (π, π). This problem is highly nontrivial because the system at criticality displays a non-Fermi-liquid behavior and because the effective coupling constant λ for the pairing is generally of order one, even when the actual interaction is smaller than fermionic bandwidth. Previous study [M. A. Metlitski and S. Sachdev, Phys. Rev. B 82, 075128 (2010)] has found that the renormalizations of the pairing vertex are stronger than in BCS theory and hold in powers of log(2)(1/T). We analyze the full gap equation and argue that summing up of the leading logarithms does not lead to a pairing instability. Yet, we show that superconductivity has no threshold and appears even if λ is set to be small, because subleading logarithmical renormalizations diverge and give rise to a BCS-like result log1/T(c) ∝ 1/λ. We argue that the analogy with BCS is not accidental as at small λ superconductivity at a QCP predominantly comes from fermions that retain Fermi-liquid behavior at criticality. We compute T(c) for the actual λ ∼ O(1), and find that both Fermi-liquid and non-Fermi-liquid fermions contribute to the pairing.
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Interplay of superconductivity and Spin-Density-Wave order in doped graphene
Physical Review B, 2012Co-Authors: Rahul Nandkishore, Andrey V. ChubukovAbstract:We study the interplay between superconductivity and Spin Density Wave order in graphene doped to 3/8 or 5/8 filling (a Van Hove doping). At this doping level, the system is known to exhibit weak coupling instabilities to both chiral d + id superconductivity and to a uniaxial Spin Density Wave. Right at van Hove doping, the superconducting instability is strongest and emerges at the highest Tc, but slightly away from van-Hove doping a Spin-Density-Wave likely emerges first. We investigate whether at some lower temperature superconductivity and Spin-Density-Waves co-exist. We derive the Landau-Ginzburg functional describing interplay of the two order parameters. Our calculations show that superconductivity and Spin Density Wave order do not co-exist and are separated by first-order transitions, either as a function of doping or as a function of T.
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itinerant half metal Spin Density Wave state on the hexagonal lattice
Physical Review Letters, 2012Co-Authors: Rahul Nandkishore, Giawei Chern, Andrey V. ChubukovAbstract:: We consider electrons on a honeycomb or triangular lattice doped to the saddle point of the band structure. We assume the system parameters are such that Spin Density Wave (SDW) order emerges below a temperature T(N) and investigate the nature of the SDW phase. We argue that at T≤T(N), the system develops a uniaxial SDW phase whose ordering pattern breaks O(3)×Z(4) symmetry and corresponds to an eight-site unit cell with nonuniform Spin moments on different sites. This state is a half-metal--it preserves the full original Fermi surface, but has gapless charged excitations in one Spin branch only. It allows for electrical control of Spin currents and is desirable for nanoscience.
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itinerant half metal Spin Density Wave state on the hexagonal lattice
APS, 2012Co-Authors: Rahul Nandkishore, Giawei Chern, Andrey V. ChubukovAbstract:We consider electrons on a honeycomb or triangular lattice doped to the saddle point of the band structure. We assume the system parameters are such that Spin Density Wave (SDW) order emerges below a temperature ${T}_{N}$ and investigate the nature of the SDW phase. We argue that at $T\ensuremath{\le}{T}_{N}$, the system develops a uniaxial SDW phase whose ordering pattern breaks $O(3)\ifmmode\times\else\texttimes\fi{}{Z}_{4}$ symmetry and corresponds to an eight-site unit cell with nonuniform Spin moments on different sites. This state is a half-metal---it preserves the full original Fermi surface, but has gapless charged excitations in one Spin branch only. It allows for electrical control of Spin currents and is desirable for nanoscience.
Yi Zhang - One of the best experts on this subject based on the ideXlab platform.
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chiral Spin Density Wave order on the frustrated honeycomb and bilayer triangle lattice hubbard model at half filling
Physical Review Letters, 2015Co-Authors: Kun Jiang, Sen Zhou, Yi Zhang, Ziqiang WangAbstract:We study the Hubbard model on the frustrated honeycomb lattice with nearest-neighbor hopping t_{1} and second nearest-neighbor hopping t_{2}, which is isomorphic to the bilayer triangle lattice, using the SU(2)-invariant slave boson theory. We show that the Coulomb interaction U induces antiferromagnetic (AF) chiral Spin Density Wave (χSDW) order in a wide range of κ=t_{2}/t_{1} where both the two-sublattice AF order at small κ and the decoupled three-sublattice 120° order at large κ are strongly frustrated, leading to three distinct phases with different anomalous Hall responses. We find a continuous transition from a χSDW semimetal with the anomalous Hall effect to a topological chiral Chern insulator exhibiting the quantum anomalous Hall effect, followed by a discontinuous transition to a χSDW insulator with a zero total Chern number but an anomalous ac Hall effect. The χSDW is likely a generic phase of strongly correlated and highly frustrated hexagonal lattice electrons.
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chiral Spin Density Wave order on the frustrated honeycomb and bilayer triangle lattice hubbard model at half filling
Physical Review Letters, 2015Co-Authors: Kun Jiang, Sen Zhou, Yi Zhang, Ziqiang WangAbstract:We study the Hubbard model on the frustrated honeycomb lattice with nearest-neighbor hopping ${t}_{1}$ and second nearest-neighbor hopping ${t}_{2}$, which is isomorphic to the bilayer triangle lattice, using the SU(2)-invariant slave boson theory. We show that the Coulomb interaction $U$ induces antiferromagnetic (AF) chiral Spin Density Wave ($\ensuremath{\chi}\mathrm{SDW}$) order in a wide range of $\ensuremath{\kappa}={t}_{2}/{t}_{1}$ where both the two-sublattice AF order at small $\ensuremath{\kappa}$ and the decoupled three-sublattice 120\ifmmode^\circ\else\textdegree\fi{} order at large $\ensuremath{\kappa}$ are strongly frustrated, leading to three distinct phases with different anomalous Hall responses. We find a continuous transition from a $\ensuremath{\chi}\mathrm{SDW}$ semimetal with the anomalous Hall effect to a topological chiral Chern insulator exhibiting the quantum anomalous Hall effect, followed by a discontinuous transition to a $\ensuremath{\chi}\mathrm{SDW}$ insulator with a zero total Chern number but an anomalous ac Hall effect. The $\ensuremath{\chi}\mathrm{SDW}$ is likely a generic phase of strongly correlated and highly frustrated hexagonal lattice electrons.
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dynamic competition between Spin Density Wave order and superconductivity in underdoped ba 1 x k x fe 2 as 2
Nature Communications, 2014Co-Authors: Yi Zhang, Zhongkai Liu, Xin Ding, Jiunhaw Chu, A F Kemper, N Plonka, Brian MoritzAbstract:Whether superconductivity coexists or competes with other types of order in unconventional superconductors is a question that has been hotly contested. An ARPES study reported by Yi et al. suggest that superconductivity and Spin-Density Wave orders coexist and compete dynamically in Ba1−xKxFe2As2.
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anisotropic but nodeless superconducting gap in the presence of Spin Density Wave in iron pnictide superconductor nafe 1 x co x as
Physical Review X, 2013Co-Authors: Yi Zhang, Chenglin Zhang, Juan Jiang, B P Xie, Yu Song, Pengcheng Dai, D L FengAbstract:The coexisting regime of Spin-Density Wave (SDW) and superconductivity in iron pnictides represents a novel ground state. We have performed high-resolution angle-resolved photoemission measurements on NaFe1-xCoxAs (x = 0.0175) in this regime and revealed its distinctive electronic structure, which provides some microscopic understandings of its behavior. The SDW signature and the superconducting gap are observed on the same bands, illustrating the intrinsic nature of the coexistence. However, because the SDW and superconductivity are manifested in different parts of the band structure, their competition is nonexclusive. Particularly, we find that the gap distribution is anisotropic and nodeless, in contrast to the isotropic superconducting gap observed in a SDW-free NaFe1-xCoxAs (x = 0.045), which puts strong constraints on theory. DOI.10.1103/PhysRevX.3.011020
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electronic structure and unusual exchange splitting in the Spin Density Wave state of the bafe2as2 parent compound of iron based superconductors
Physical Review Letters, 2009Co-Authors: L X Yang, Yi Zhang, H W Ou, J F Zhao, D W Shen, Bo Zhou, F Chen, Min Xu, Cheng He, Yu ChenAbstract:The magnetic properties in the parent compounds are often intimately related to the microscopic mechanism of superconductivity. Here we report the first direct measurements on the electronic structure of a parent compound of the newly discovered iron-based superconductor, BaFe2As2, which provides a foundation for further studies. We show that the energy of the Spin Density Wave in BaFe2As2 is mainly lowered through exotic exchange splitting of the band structure.
Subir Sachdev - One of the best experts on this subject based on the ideXlab platform.
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Spin Density Wave order topological order and fermi surface reconstruction
Physical Review B, 2016Co-Authors: Subir Sachdev, Shubhayu Chatterjee, Erez Berg, Yoni SchattnerAbstract:In the conventional theory of Density Wave ordering in metals, the onset of Spin Density Wave (SDW) order coincides with the reconstruction of the Fermi surfaces into small ``pockets.'' We present models which display this transition, while also displaying an alternative route between these phases via an intermediate phase with topological order, no broken symmetry, and pocket Fermi surfaces. The models involve coupling emergent gauge fields to a fractionalized SDW order, but retain the canonical electron operator in the underlying Hamiltonian. We establish an intimate connection between the suppression of certain defects in the SDW order and the presence of Fermi surface sizes distinct from the Luttinger value in Fermi liquids. We discuss the relevance of such models to the physics of the hole-doped cuprates near optimal doping.
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hyperscaling at the Spin Density Wave quantum critical point in two dimensional metals
Physical Review B, 2015Co-Authors: Aavishkar A Patel, Subir Sachdev, Philipp StrackAbstract:The hyperscaling property implies that spatially isotropic critical quantum states in $d$ spatial dimensions have a specific heat, which scales with temperature as ${T}^{d/z}$, and an optical conductivity, which scales with frequency as ${\ensuremath{\omega}}^{(d\ensuremath{-}2)/z}$ for $\ensuremath{\omega}\ensuremath{\gg}T$, where $z$ is the dynamic critical exponent. We examine the Spin Density Wave critical fixed point of metals in $d=2$ found by Sur and Lee [Phys. Rev. B 91, 125136 (2015)] in an expansion in $\ensuremath{\epsilon}=3\ensuremath{-}d$. We find that the contributions of the ``hot spots'' on the Fermi surface to the optical conductivity and specific heat obey hyperscaling (up to logarithms), and agree with the results of the large $N$ analysis of the optical conductivity by Hartnoll et al. [ Phys. Rev. B 84, 125115 (2011)]. With a small bare velocity of the boson associated with the Spin Density Wave order, there is an intermediate energy regime where hyperscaling is violated with $d\ensuremath{\rightarrow}{d}_{t}$, where ${d}_{t}=1$ is the number of dimensions transverse to the Fermi surface. We also present a Boltzmann equation analysis which indicates that the hot-spot contribution to the dc conductivity has the same scaling as the optical conductivity, with $T$ replacing $\ensuremath{\omega}$.
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dc resistivity at the onset of Spin Density Wave order in two dimensional metals
Physical Review B, 2014Co-Authors: Aavishkar A Patel, Subir SachdevAbstract:The theory for the onset of Spin Density Wave order in a metal in two dimensions flows to strong coupling, with strong interactions not only at the “hot spots,” but on the entire Fermi surface. We advocate the computation of dc transport in a regime where there is rapid relaxation to local equilibrium around the Fermi surface by processes which conserve total momentum. The dc resistivity is then controlled by weaker perturbations which do not conserve momentum. We consider variations in the local position of the quantum-critical point, induced by long-Wavelength disorder, and find a contribution to the resistivity which is linear in temperature (up to logarithmic corrections) at low temperature. Scattering of fermions between hot spots, by short-Wavelength disorder, leads to a residual resistivity and a correction which is linear in temperature.
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quantum critical response at the onset of Spin Density Wave order in two dimensional metals
Physical Review B, 2011Co-Authors: Sean A Hartnoll, Max A Metlitski, Diego M Hofman, Subir SachdevAbstract:We study the frequency dependence of the electron self energy and the optical conductivity in a recently developed eld theory of the Spin Density Wave quantum phase transition in twodimensional metals. We focus on the interplay between the Fermi surface ‘hot spots’ and the
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quantum critical response at the onset of Spin Density Wave order in two dimensional metals
Physical Review B, 2011Co-Authors: Sean A Hartnoll, Max A Metlitski, Diego M Hofman, Subir SachdevAbstract:We study the frequency dependence of the electron self-energy and the optical conductivity in a recently developed field theory of the Spin-Density-Wave quantum phase transition in two-dimensional metals. We focus on the interplay between the Fermi surface ``hot spots'' and the remainder of the ``cold'' Fermi surface. Scattering of electrons off the fluctuations of the Spin-Density-Wave order parameter, $\ensuremath{\varphi}$, is strongest at the hot spots; we compute the conductivity due to this scattering in a rainbow approximation. We point out the importance of composite operators, built of products of the primary electron or $\ensuremath{\varphi}$ fields: These have important effects also away from the hot spots. The simplest composite operator, ${\ensuremath{\varphi}}^{2}$, leads to deviations from Landau Fermi-liquid behavior on the entire Fermi surface. We also find an intermediate frequency window in which the cold electrons lose their quasiparticle form due to effectively one-dimensional scattering processes. The latter processes are part of umklapp scattering, which leads to singular contributions to the optical conductivity at the lowest frequencies at zero temperature.
Ziqiang Wang - One of the best experts on this subject based on the ideXlab platform.
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chiral Spin Density Wave order on the frustrated honeycomb and bilayer triangle lattice hubbard model at half filling
Physical Review Letters, 2015Co-Authors: Kun Jiang, Sen Zhou, Yi Zhang, Ziqiang WangAbstract:We study the Hubbard model on the frustrated honeycomb lattice with nearest-neighbor hopping ${t}_{1}$ and second nearest-neighbor hopping ${t}_{2}$, which is isomorphic to the bilayer triangle lattice, using the SU(2)-invariant slave boson theory. We show that the Coulomb interaction $U$ induces antiferromagnetic (AF) chiral Spin Density Wave ($\ensuremath{\chi}\mathrm{SDW}$) order in a wide range of $\ensuremath{\kappa}={t}_{2}/{t}_{1}$ where both the two-sublattice AF order at small $\ensuremath{\kappa}$ and the decoupled three-sublattice 120\ifmmode^\circ\else\textdegree\fi{} order at large $\ensuremath{\kappa}$ are strongly frustrated, leading to three distinct phases with different anomalous Hall responses. We find a continuous transition from a $\ensuremath{\chi}\mathrm{SDW}$ semimetal with the anomalous Hall effect to a topological chiral Chern insulator exhibiting the quantum anomalous Hall effect, followed by a discontinuous transition to a $\ensuremath{\chi}\mathrm{SDW}$ insulator with a zero total Chern number but an anomalous ac Hall effect. The $\ensuremath{\chi}\mathrm{SDW}$ is likely a generic phase of strongly correlated and highly frustrated hexagonal lattice electrons.
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chiral Spin Density Wave order on the frustrated honeycomb and bilayer triangle lattice hubbard model at half filling
Physical Review Letters, 2015Co-Authors: Kun Jiang, Sen Zhou, Yi Zhang, Ziqiang WangAbstract:We study the Hubbard model on the frustrated honeycomb lattice with nearest-neighbor hopping t_{1} and second nearest-neighbor hopping t_{2}, which is isomorphic to the bilayer triangle lattice, using the SU(2)-invariant slave boson theory. We show that the Coulomb interaction U induces antiferromagnetic (AF) chiral Spin Density Wave (χSDW) order in a wide range of κ=t_{2}/t_{1} where both the two-sublattice AF order at small κ and the decoupled three-sublattice 120° order at large κ are strongly frustrated, leading to three distinct phases with different anomalous Hall responses. We find a continuous transition from a χSDW semimetal with the anomalous Hall effect to a topological chiral Chern insulator exhibiting the quantum anomalous Hall effect, followed by a discontinuous transition to a χSDW insulator with a zero total Chern number but an anomalous ac Hall effect. The χSDW is likely a generic phase of strongly correlated and highly frustrated hexagonal lattice electrons.
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electron correlation and Spin Density Wave order in iron pnictides
Physical Review Letters, 2010Co-Authors: Sen Zhou, Ziqiang WangAbstract:We study the correlation effects on the electronic structure, orbital and Spin Density Wave (SDW) order in Fe pnictides. Using the multiorbital Hubbard model and Gutzwiller projection, we show that correlation effects are essential to stabilize the metallic SDW phase for the intermediate correlation strengths appropriate for pnictides. We find that the ordered moments depend sensitively on Hund's rule coupling J but weakly on the intraorbital Coulomb repulsion U, varying from 0.3μ B to 1.5μ B in the range J = 0.3-0.8 eV for U = 3-4 eV. We study the phase diagram, the evolution of the Fermi surface with the ordered moment, the effects of electron doping, and compare to recent experiments.
Sen Zhou - One of the best experts on this subject based on the ideXlab platform.
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antiferromagnetic chiral Spin Density Wave and strain induced chern insulator in the square lattice hubbard model with frustration
Physical Review B, 2020Co-Authors: Yunpeng Huang, Jinwei Dong, Panagiotis Kotetes, Sen ZhouAbstract: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 ${t}^{\ensuremath{'}}/t=1/\sqrt{2}$, where the Fermi surface is well nested for both $(\ensuremath{\pi},\ensuremath{\pi})$ and $(\ensuremath{\pi},0)/(0,\ensuremath{\pi})$ Wave vectors. This triple-$\mathbf{Q}$ chiral phase is sandwiched by a single-$\mathbf{Q}$ N\'eel phase and a double-$\mathbf{Q}$ 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 $(\frac{\ensuremath{\pi}}{2},\frac{\ensuremath{\pi}}{2})$ of the Brillouin zone. We demonstrate that the application of a diagonal strain induces a ${d}_{xy}$-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 $\ifmmode\pm\else\textpm\fi{}1$. 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 $\frac{3}{4}$ filling, the triple-$\mathbf{Q}$ chiral phase yields a Chern insulator exhibiting the quantum anomalous Hall effect.
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antiferromagnetic chiral Spin Density Wave and strain induced chern insulator in the square lattice hubbard model with frustration
arXiv: Strongly Correlated Electrons, 2019Co-Authors: Yunpeng Huang, Jinwei Dong, Panagiotis Kotetes, Sen ZhouAbstract: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 $t'/t$ between the nearest and next nearest neighbor hoppings $t$ and $t'$. 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 $t'/t=1/\sqrt{2}$, where the Fermi surface is well-nested for both $(\pi,\pi)$ and $(\pi,0)/(0,\pi)$ Wave vectors. This triple-${\bf Q}$ chiral phase is sandwiched by a single-${\bf Q}$ Neel phase and a double-${\bf Q}$ coplanar Spin-vortex crystal phase, at smaller and larger $t'/t$, 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 $({\pi \over 2},{\pi\over 2})$ of the Brillouin zone. We demonstrate that the application of a diagonal strain induces a $d_{xy}$-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 $\pm1$. At half-filling, this leads to a zero total Chern number and renders the topologically-notrivial properties observable only in the ac response regime. Instead, we show that at $3/4$ filling, the triple-${\bf Q}$ chiral phase yields a Chern insulator exhibiting the quantum anomalous Hall effect.
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chiral Spin Density Wave order on the frustrated honeycomb and bilayer triangle lattice hubbard model at half filling
Physical Review Letters, 2015Co-Authors: Kun Jiang, Sen Zhou, Yi Zhang, Ziqiang WangAbstract:We study the Hubbard model on the frustrated honeycomb lattice with nearest-neighbor hopping t_{1} and second nearest-neighbor hopping t_{2}, which is isomorphic to the bilayer triangle lattice, using the SU(2)-invariant slave boson theory. We show that the Coulomb interaction U induces antiferromagnetic (AF) chiral Spin Density Wave (χSDW) order in a wide range of κ=t_{2}/t_{1} where both the two-sublattice AF order at small κ and the decoupled three-sublattice 120° order at large κ are strongly frustrated, leading to three distinct phases with different anomalous Hall responses. We find a continuous transition from a χSDW semimetal with the anomalous Hall effect to a topological chiral Chern insulator exhibiting the quantum anomalous Hall effect, followed by a discontinuous transition to a χSDW insulator with a zero total Chern number but an anomalous ac Hall effect. The χSDW is likely a generic phase of strongly correlated and highly frustrated hexagonal lattice electrons.
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chiral Spin Density Wave order on the frustrated honeycomb and bilayer triangle lattice hubbard model at half filling
Physical Review Letters, 2015Co-Authors: Kun Jiang, Sen Zhou, Yi Zhang, Ziqiang WangAbstract:We study the Hubbard model on the frustrated honeycomb lattice with nearest-neighbor hopping ${t}_{1}$ and second nearest-neighbor hopping ${t}_{2}$, which is isomorphic to the bilayer triangle lattice, using the SU(2)-invariant slave boson theory. We show that the Coulomb interaction $U$ induces antiferromagnetic (AF) chiral Spin Density Wave ($\ensuremath{\chi}\mathrm{SDW}$) order in a wide range of $\ensuremath{\kappa}={t}_{2}/{t}_{1}$ where both the two-sublattice AF order at small $\ensuremath{\kappa}$ and the decoupled three-sublattice 120\ifmmode^\circ\else\textdegree\fi{} order at large $\ensuremath{\kappa}$ are strongly frustrated, leading to three distinct phases with different anomalous Hall responses. We find a continuous transition from a $\ensuremath{\chi}\mathrm{SDW}$ semimetal with the anomalous Hall effect to a topological chiral Chern insulator exhibiting the quantum anomalous Hall effect, followed by a discontinuous transition to a $\ensuremath{\chi}\mathrm{SDW}$ insulator with a zero total Chern number but an anomalous ac Hall effect. The $\ensuremath{\chi}\mathrm{SDW}$ is likely a generic phase of strongly correlated and highly frustrated hexagonal lattice electrons.
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electron correlation and Spin Density Wave order in iron pnictides
Physical Review Letters, 2010Co-Authors: Sen Zhou, Ziqiang WangAbstract:We study the correlation effects on the electronic structure, orbital and Spin Density Wave (SDW) order in Fe pnictides. Using the multiorbital Hubbard model and Gutzwiller projection, we show that correlation effects are essential to stabilize the metallic SDW phase for the intermediate correlation strengths appropriate for pnictides. We find that the ordered moments depend sensitively on Hund's rule coupling J but weakly on the intraorbital Coulomb repulsion U, varying from 0.3μ B to 1.5μ B in the range J = 0.3-0.8 eV for U = 3-4 eV. We study the phase diagram, the evolution of the Fermi surface with the ordered moment, the effects of electron doping, and compare to recent experiments.