Evidence of Potts-Nematic Superfluidity in a Hexagonal $sp^2$ Optical Lattice

Jin, Shengjie; Zhang, Wenjun; Guo, Xinxin; Chen, Xuzong; Zhou, Xiaoji; Li, Xiaopeng

doi:10.48550/arxiv.1910.11880

Cited by 5 publications

(6 citation statements)

References 15 publications

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“…For d-wave charge Pomeranchuck order, we introduce two real order parameters ϕ 2 , ϕ 3 and the total order parameter is ϕ c = ϕ 2 Γ 2 + ϕ 3 Γ 3 . A hexagonal lattice allows for a cubic term in the free energy [27][28][29][30][31][32] . Keeping this term and neglecting ϕ 4 terms, we obtain…”

Section: Ft Range Of Stabilitymentioning

confidence: 99%

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Competing orders at higher-order Van Hove points

Classen,

Chubukov,

Honerkamp

et al. 2020

Preprint

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Van Hove points are special points in the energy dispersion, where the density of states exhibits analytic singularities. When a Van Hove point is close to the Fermi level, tendencies towards density wave orders, Pomeranchuk orders, and superconductivity can all be enhanced, often in more than one channel, leading to a competition between different orders and unconventional ground states. Here we consider the effects from higher-order Van Hove points, around which the dispersion is flatter than near a conventional Van Hove point, and the density of states has a power-law divergence. We argue that such points are present in intercalated graphene and other materials. We use an effective lowenergy model for electrons near higher-order Van Hove points and analyze the competition between different ordering tendencies using an unbiased renormalization group approach. For purely repulsive interactions, we find that two key competitors are ferromagnetism and chiral superconductivity. For a small attractive exchange interaction, we find a new type of spin Pomeranchuk order, in which the spin order parameter winds around the Fermi surface. The supermetal state, predicted for a single higher-order Van Hove point, is an unstable fixed point in our case.

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Section: Ft Range Of Stabilitymentioning

confidence: 99%

“…Each state selects one particular HOVH point where the order is largest. Such a state breaks lattice C 3 rotational symmetry and is a charge nematic [27][28][29][30][31][32] .…”

Section: Ft Range Of Stabilitymentioning

confidence: 99%

Competing orders at higher-order Van Hove points

Classen,

Chubukov,

Honerkamp

et al. 2020

Preprint

View full text Add to dashboard Cite

show abstract

“…In contrast, because ψ is complex and transforms as the A 1 irrep of D 6 , such a cubic term is not allowed in the charge-4e action. This cubic term not only favors the nematic order over the charge-4e order, but it also lowers the symmetry of the nematic order parameter from U(1) to 3-state Potts [20,23,40,42]. At first sight, this seems to suggest that it would be challenging to find a vestigial charge-4e instability occurring before the onset of vestigial nematic order.…”

mentioning

confidence: 99%

Charge- 4e Superconductivity from Multicomponent Nematic Pairing: Application to Twisted Bilayer Graphene

Fernandes

2021

Phys. Rev. Lett.

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We show that unconventional nematic superconductors with multi-component order parameter in lattices with three-fold and six-fold rotational symmetries support a charge-4e vestigial superconducting phase above Tc. The charge-4e state, which is a condensate of four-electron bound states that preserve the rotational symmetry of the lattice, is nearly degenerate with a competing vestigial nematic state, which is non-superconducting and breaks the rotational symmetry. This robust result is the consequence of a hidden discrete symmetry in the Ginzburg-Landau theory, which permutes quantities in the gauge sector and in the crystalline sector of the symmetry group. We argue that random strain generally favors the charge-4e state over the nematic phase, as it acts as a random-mass to the former but as a random-field to the latter. Thus, we propose that twodimensional inhomogeneous systems displaying nematic superconductivity, such as twisted bilayer graphene, provide a promising platform to realize the elusive charge-4e superconducting phase.

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“…Although this parametrization might suggest that Φ is an XY order parameter, the lattice symmetries of TBG introduce crystal anisotropy effects that pin the nematic director to a discrete set of high-symmetry directions. Indeed, the Landau-type action S nem [Φ] is (see also [40,[52][53][54]):…”

mentioning

confidence: 99%

Nematicity with a twist: rotational symmetry breaking in a moiré superlattice

Fernandes,

Venderbos

2019

Preprint

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Motivated by recent reports of nematic order in twisted bilayer graphene (TBG), we investigate the impact of the triangular moiré superlattice degrees of freedom on nematicity. In TBG, the nematic order parameter is not Ising-like, as it is the case in tetragonal crystals, but has a 3-state Potts character related to the threefold rotational symmetry (C3z) of the moiré superlattice. We find that even in the presence of static strain that explicitly breaks the C3z symmetry, the system can still undergo a nematic-flop phase transition that spontaneously breaks in-plane twofold rotations. Moreover, elastic fluctuations, manifested as acoustic phonons, mediate a nemato-orbital coupling that ties the orientation of the nematic director to certain soft directions in momentum space, rendering the Potts-nematic transition mean-field and first-order. In contrast to the case of rigid crystals, the Fermi-surface hot-spots associated with these soft directions are maximally coupled to the low-energy nematic fluctuations in the case of the moiré superlattice.

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Evidence of Potts-Nematic Superfluidity in a Hexagonal $sp^2$ Optical Lattice

Cited by 5 publications

References 15 publications

Competing orders at higher-order Van Hove points

Competing orders at higher-order Van Hove points

Charge- 4e Superconductivity from Multicomponent Nematic Pairing: Application to Twisted Bilayer Graphene

Nematicity with a twist: rotational symmetry breaking in a moiré superlattice

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