Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:1405.5880 · Physical Review B

Emergent dome of nematic order around a quantum anomalous Hall critical point

Ashley M. Cook, Ciarán Hickey, Arun Paramekanti

Published Aug 27, 2014• 14 citations
arXivHTMLPDF

Abstract

Motivated by the experimental discovery of the quantum anomalous Hall effect and the interest in quantum phase transitions of correlated electrons, we consider interaction effects at a quantum anomalous Hall critical point. We study a microscopic lattice model of spinful fermions on the triangular lattice which exhibits a $C=2$ Chern insulator (CI) phase with a quantized anomalous Hall effect, sandwiched between two normal insulator (NI) phases. The first NI-CI quantum phase transition is driven by simultaneous mass inversion of a pair of Dirac fermions, with short range interactions being perturbatively irrelevant at the transition. The second CI-NI transition is driven by a quadratic band touching point protected by momentum space topology and ${C}_{6}$ lattice symmetry. A one-loop renormalization group analysis shows that short range interactions lead to a single marginally relevant perturbation at this transition. We obtain the mean field phase diagram of this model incorporating weak repulsive Hubbard interactions, finding an emergent dome of nematic order around this CI-NI topological critical point. We discuss the crossovers in the Hall conductivity at nonzero temperature, and the Landau theory of the quantum and thermal transitions out of the nematic phase. Our results may be relevant to ferromagnetic double perovskite films with spin-orbit coupling which have been proposed to host such a Chern transition. Our work provides perhaps the simplest example of an emergent phase near a quantum critical point.

DOI
10.1103/physrevb.90.085145

Related papers

Tuning topological phase and quantum anomalous Hall effect by interaction in quadratic band touching systems

Tian-Sheng Zeng, Wei Zhu, Donna Sheng

Abstract Interaction-driven topological phases significantly enrich the class of topological materials and thus are of great importance. Here, we study the phase diagram of interacting spinless fermions filling the two-dimensional checkerboard lattice with a quadratic band touching (QBT) point. By developing new diagnosis based on the state-of-the-art density-matrix renormalization group and exact diagonalization, we determine accurate quantum phase diagram for such a system at half-filling with three distinct phases. For weak nearest-neighboring interactions, we demonstrate the instability of the QBT towards an interaction-driven spontaneous quantum anomalous Hall (QAH) effect. For strong interactions, the system breaks the rotational symmetry realizing a nematic charge-density-wave (CDW) phase. Interestingly, for intermediate interactions we discover a symmetry-broken bond-ordered critical phase sandwiched in between the QAH and CDW phases, which splits the QBT into two Dirac points driven by interaction. Instead of the direct transition between QAH and CDW phases, our identification of an intermediate phase sheds new light on the theoretical understanding of the interaction-driven phases in QBT systems.

arXiv:1805.01101•npj Quantum Materials•Sep 17, 2018•38 citations

Nematic order in topological Sachdev-Ye-Kitaev models

Andrew Hardy, Anjishnu Bose, Arun Paramekanti

We study a class of multiorbital models based on those proposed by Venderbos et al. [Phys. Rev. B 98, 235160 (2018)] which exhibit an interplay of topology, interactions, and fermion incoherence. In the noninteracting limit, these models exhibit trivial and Chern insulator phases with Chern number $C\ensuremath{\ge}1$ bands as determined by the relative angular momentum of the participating orbitals. These quantum anomalous Hall insulator phases are separated by topological transitions protected by crystalline rotation symmetry, featuring Dirac or quadratic band-touching points. Here we study the impact of Sachdev-Ye-Kitaev (SYK) type interactions on these lattice models. Given the random interactions, these models display average symmetries upon disorder averaging, including a charge conjugation symmetry, so they behave as interacting models in topological class $\mathbf{D}$ enriched by crystalline rotation symmetry. The phase diagram of this model features a non-Fermi liquid at high temperature and an exciton condensate with nematic transport at low temperature. We present results from the free energy, spectral functions, and the anomalous Hall resistivity as a function of temperature and tuning parameters. Our results are broadly relevant to correlated topological matter in multiorbital systems, and may also be viewed, with a suitable particle hole transformation, as an exploration of strong interaction effects on mean-field topological superconductors.

arXiv:2308.13601•Physical review. B./Physical review. B•Dec 26, 2023•1 citation

Quantum anomalous Hall phase stabilized via realistic interactions on a kagome lattice

Yafei Ren, Tian-Sheng Zeng, W. Zhu +1 more

We study the quantum phases of spinless fermions at one-third filling on a kagome lattice featuring a quadratic band touching Fermi point. In the presence of weak first and second nearest-neighbor repulsive interactions (${V}_{1}$ and ${V}_{2}$), we demonstrate an interaction driven quantum anomalous Hall effect by employing exact diagonalization and density-matrix renormalization group methods. The time-reversal symmetry is broken spontaneously by forming loop currents that exhibit long-range correlation. Quantized Hall conductance corresponding to a Chern number of $\ifmmode\pm\else\textpm\fi{}1$ is obtained by measuring the pumped charge through inserting flux in a cylinder geometry. We find that the energy gap, which topologically protects the emerging ground states, can be enhanced remarkably by a moderate ${V}_{2}<{V}_{1}$ via calculating the spectrum and charge excitation gaps, which highlights the experimentally feasible scheme of realizing the interaction driven topological phase by spatially decaying interactions on topologically trivial lattice models.

arXiv:1806.11094•Physical review. B./Physical review. B•Nov 26, 2018•16 citations

Quantum anomalous Hall insulator stabilized by competing interactions

Shouvik Sur, Shou-Shu Gong, Kun Yang +1 more

We study the quantum phases driven by interaction in a semimetal with a quadratic band touching at the Fermi level. By combining the density matrix renormalization group (DMRG), analytical power expanded Gibbs potential method, and the weak coupling renormalization group, we study a spinless fermion system on a checkerboard lattice at half-filling, which has a quadratic band touching in the absence of interaction. In the presence of strong nearest-neighbor (${V}_{1}$) and next-nearest-neighbor (${V}_{2}$) interactions, we identify a site nematic insulator phase, a stripe insulator phase, and a phase separation region, in agreement with the phase diagram obtained analytically in the strong coupling limit (i.e., in the absence of fermion hopping). In the intermediate interaction regime we establish a quantum anomalous Hall phase in the DMRG as evidenced by the spontaneous time-reversal symmetry breaking and the appearance of a quantized Chern number $C=1$. For weak interaction we utilize the power expanded Gibbs potential method that treats ${V}_{1}$ and ${V}_{2}$ on equal footing, as well as the weak coupling renormalization group. Our analytical results reveal that not only the repulsive ${V}_{1}$ interaction, but also the ${V}_{2}$ interaction (both repulsive and attractive), can drive the quantum anomalous Hall phase. We also determine the phase boundary in the ${V}_{1}\text{\ensuremath{-}}{V}_{2}$ plane that separates the semimetal from the quantum anomalous Hall state. Finally, we show that the nematic semimetal, which was proposed for $|{V}_{2}|\ensuremath{\gg}{V}_{1}$ at weak coupling in a previous study, is absent, and the quantum anomalous Hall state is the only weak coupling instability of the spinless quadratic band touching semimetal.

arXiv:1805.01116•Physical review. B./Physical review. B•Sep 26, 2018•28 citations

Topological Insulators and Nematic Phases from Spontaneous Symmetry Breaking in 2D Fermi Systems with a Quadratic Band Crossing

Kai Sun, Hong Yao, Eduardo Fradkin +1 more

We investigate the stability of a quadratic band-crossing point (QBCP) in 2D fermionic systems. At the noninteracting level, we show that a QBCP exists and is topologically stable for a Berry flux +/-2pi if the point symmetry group has either fourfold or sixfold rotational symmetries. This putative topologically stable free-fermion QBCP is marginally unstable to arbitrarily weak short-range repulsive interactions. We consider both spinless and spin-1/2 fermions. Four possible ordered states result: a quantum anomalous Hall phase, a quantum spin Hall phase, a nematic phase, and a nematic-spin-nematic phase.

arXiv:0905.0907•Physical Review Letters•Jul 24, 2009•445 citations

Emergent relativistic symmetry from interacting fermions on the honeycomb bilayer

Zi Hong Liu, Lukas Janssen

We study the phase diagram of interacting spinless fermions on the honeycomb bilayer at charge neutrality using large-scale quantum Monte Carlo simulations. In the noninteracting limit, the low-energy spectrum features quadratically dispersing bands that touch at the corners of the hexagonal Brillouin zone. Weak to intermediate interactions induce a splitting of each of the quadratic band touching points into four Dirac points, located along high-symmetry directions of the reciprocal lattice. Strong interactions lead to the formation of a layer-polarized charge density wave, which spontaneously breaks the $\mathbb Z_2$ layer inversion symmetry and opens an insulating gap in the spectrum. We show that the semimetal-to-insulator quantum phase transition as a function of interaction is continuous and characterized by emergent relativistic symmetry. Our results for the values of the correlation-length exponent $ν$, the order-parameter anomalous dimension $η_ϕ$, and the fermion anomalous dimension $η_ψ$ agree with those of the theoretically predicted 2+1D Gross-Neveu-Ising universality class with eight two-component Dirac fermions within less than 5\%\ deviation. We also determine the crossover scale as a function of interaction strength between the nonrelativistic semimetal state at high temperatures, characterized by dynamical critical exponent $z = 2$, and the Dirac semimetal state at intermediates temperatures, characterized by $z=1$. Further reducing the temperature below the crossover scale at a fixed value of the interaction strength above the quantum critical point results in a classical ordering transition in the 2D Ising universality class.

arXiv:2603.22259•Physical review. B./Physical review. B•Sep 22, 2026•0 citations
Motivated by the experimental discovery of the quantum anomalous Hall effect and the interest in quantum phase transitions of correlated electrons, we consider interaction effects at a quantum anomalous Hall critical point. We study a microscopic lattice model of spinful fermions on the triangular lattice which exhibits a C=2C=2C=2 Chern insulator (CI) phase with a quantized anomalous Hall effect, sandwiched between two normal insulator (NI) phases. The first NI-CI quantum phase transition is driven by simultaneous mass inversion of a pair of Dirac fermions, with short range interactions being perturbatively irrelevant at the transition. The second CI-NI transition is driven by a quadratic band touching point protected by momentum space topology and C6{C}_{6}C6​ lattice symmetry. A one-loop renormalization group analysis shows that short range interactions lead to a single marginally relevant perturbation at this transition. We obtain the mean field phase diagram of this model incorporating weak repulsive Hubbard interactions, finding an emergent dome of nematic order around this CI-NI topological critical point. We discuss the crossovers in the Hall conductivity at nonzero temperature, and the Landau theory of the quantum and thermal transitions out of the nematic phase. Our results may be relevant to ferromagnetic double perovskite films with spin-orbit coupling which have been proposed to host such a Chern transition. Our work provides perhaps the simplest example of an emergent phase near a quantum critical point.
Abstract Interaction-driven topological phases significantly enrich the class of topological materials and thus are of great importance. Here, we study the phase diagram of interacting spinless fermions filling the two-dimensional checkerboard lattice with a quadratic band touching (QBT) point. By developing new diagnosis based on the state-of-the-art density-matrix renormalization group and exact diagonalization, we determine accurate quantum phase diagram for such a system at half-filling with three distinct phases. For weak nearest-neighboring interactions, we demonstrate the instability of the QBT towards an interaction-driven spontaneous quantum anomalous Hall (QAH) effect. For strong interactions, the system breaks the rotational symmetry realizing a nematic charge-density-wave (CDW) phase. Interestingly, for intermediate interactions we discover a symmetry-broken bond-ordered critical phase sandwiched in between the QAH and CDW phases, which splits the QBT into two Dirac points driven by interaction. Instead of the direct transition between QAH and CDW phases, our identification of an intermediate phase sheds new light on the theoretical understanding of the interaction-driven phases in QBT systems.
We study a class of multiorbital models based on those proposed by Venderbos et al. [Phys. Rev. B 98, 235160 (2018)] which exhibit an interplay of topology, interactions, and fermion incoherence. In the noninteracting limit, these models exhibit trivial and Chern insulator phases with Chern number $C\ensuremath{\ge}1$ bands as determined by the relative angular momentum of the participating orbitals. These quantum anomalous Hall insulator phases are separated by topological transitions protected by crystalline rotation symmetry, featuring Dirac or quadratic band-touching points. Here we study the impact of Sachdev-Ye-Kitaev (SYK) type interactions on these lattice models. Given the random interactions, these models display average symmetries upon disorder averaging, including a charge conjugation symmetry, so they behave as interacting models in topological class D\mathbf{D}D enriched by crystalline rotation symmetry. The phase diagram of this model features a non-Fermi liquid at high temperature and an exciton condensate with nematic transport at low temperature. We present results from the free energy, spectral functions, and the anomalous Hall resistivity as a function of temperature and tuning parameters. Our results are broadly relevant to correlated topological matter in multiorbital systems, and may also be viewed, with a suitable particle hole transformation, as an exploration of strong interaction effects on mean-field topological superconductors.
We study the quantum phases of spinless fermions at one-third filling on a kagome lattice featuring a quadratic band touching Fermi point. In the presence of weak first and second nearest-neighbor repulsive interactions (V1{V}_{1}V1​ and V2{V}_{2}V2​), we demonstrate an interaction driven quantum anomalous Hall effect by employing exact diagonalization and density-matrix renormalization group methods. The time-reversal symmetry is broken spontaneously by forming loop currents that exhibit long-range correlation. Quantized Hall conductance corresponding to a Chern number of $\ifmmode\pm\else\textpm\fi{}1$ is obtained by measuring the pumped charge through inserting flux in a cylinder geometry. We find that the energy gap, which topologically protects the emerging ground states, can be enhanced remarkably by a moderate V2<V1{V}_{2}<{V}_{1}V2​<V1​ via calculating the spectrum and charge excitation gaps, which highlights the experimentally feasible scheme of realizing the interaction driven topological phase by spatially decaying interactions on topologically trivial lattice models.
We study the quantum phases driven by interaction in a semimetal with a quadratic band touching at the Fermi level. By combining the density matrix renormalization group (DMRG), analytical power expanded Gibbs potential method, and the weak coupling renormalization group, we study a spinless fermion system on a checkerboard lattice at half-filling, which has a quadratic band touching in the absence of interaction. In the presence of strong nearest-neighbor (V1{V}_{1}V1​) and next-nearest-neighbor (V2{V}_{2}V2​) interactions, we identify a site nematic insulator phase, a stripe insulator phase, and a phase separation region, in agreement with the phase diagram obtained analytically in the strong coupling limit (i.e., in the absence of fermion hopping). In the intermediate interaction regime we establish a quantum anomalous Hall phase in the DMRG as evidenced by the spontaneous time-reversal symmetry breaking and the appearance of a quantized Chern number C=1C=1C=1. For weak interaction we utilize the power expanded Gibbs potential method that treats V1{V}_{1}V1​ and V2{V}_{2}V2​ on equal footing, as well as the weak coupling renormalization group. Our analytical results reveal that not only the repulsive V1{V}_{1}V1​ interaction, but also the V2{V}_{2}V2​ interaction (both repulsive and attractive), can drive the quantum anomalous Hall phase. We also determine the phase boundary in the ${V}_{1}\text{\ensuremath{-}}{V}_{2}$ plane that separates the semimetal from the quantum anomalous Hall state. Finally, we show that the nematic semimetal, which was proposed for $|{V}_{2}|\ensuremath{\gg}{V}_{1}$ at weak coupling in a previous study, is absent, and the quantum anomalous Hall state is the only weak coupling instability of the spinless quadratic band touching semimetal.
We investigate the stability of a quadratic band-crossing point (QBCP) in 2D fermionic systems. At the noninteracting level, we show that a QBCP exists and is topologically stable for a Berry flux +/-2pi if the point symmetry group has either fourfold or sixfold rotational symmetries. This putative topologically stable free-fermion QBCP is marginally unstable to arbitrarily weak short-range repulsive interactions. We consider both spinless and spin-1/2 fermions. Four possible ordered states result: a quantum anomalous Hall phase, a quantum spin Hall phase, a nematic phase, and a nematic-spin-nematic phase.
We study the phase diagram of interacting spinless fermions on the honeycomb bilayer at charge neutrality using large-scale quantum Monte Carlo simulations. In the noninteracting limit, the low-energy spectrum features quadratically dispersing bands that touch at the corners of the hexagonal Brillouin zone. Weak to intermediate interactions induce a splitting of each of the quadratic band touching points into four Dirac points, located along high-symmetry directions of the reciprocal lattice. Strong interactions lead to the formation of a layer-polarized charge density wave, which spontaneously breaks the Z2\mathbb Z_2Z2​ layer inversion symmetry and opens an insulating gap in the spectrum. We show that the semimetal-to-insulator quantum phase transition as a function of interaction is continuous and characterized by emergent relativistic symmetry. Our results for the values of the correlation-length exponent ννν, the order-parameter anomalous dimension ηϕη_ϕηϕ​, and the fermion anomalous dimension ηψη_ψηψ​ agree with those of the theoretically predicted 2+1D Gross-Neveu-Ising universality class with eight two-component Dirac fermions within less than 5\%\ deviation. We also determine the crossover scale as a function of interaction strength between the nonrelativistic semimetal state at high temperatures, characterized by dynamical critical exponent z=2z = 2z=2, and the Dirac semimetal state at intermediates temperatures, characterized by z=1z=1z=1. Further reducing the temperature below the crossover scale at a fixed value of the interaction strength above the quantum critical point results in a classical ordering transition in the 2D Ising universality class.