Ladderlike optical conductivity in the spin-fermion model

Claßen, Laura; Robinson, Neil J.; Tsvelik, A. M.

doi:10.1103/physrevb.99.115110

Cited by 4 publications

(6 citation statements)

References 58 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Our results for the pairing symmetry are in agreement with Ref. 54 and they differ from the topological d + id symmetry predicted in many TBG studies [31,34,35,39,40,44,51,57,58,82] and also from other proposed symmetries which include s-wave [48-50, 53, 55, 57], extended s-wave [38,41,46,82], p-wave [53,56], p + ip-wave [37], d-wave [50,53,56], and f -wave [36,39,40,53]. Apart from Ref.…”

supporting

confidence: 88%

“…An interesting future direction of research is to include other interaction channels than pairing and explore the insulating states observed in TBG [2,3,99]. Based on our results, one can anticipate that quantum geometry and multiband processes are important in superconductivity and correlated states of other twisted multilayer materials [100][101][102][103][104][105][106][107][108][109][110][111][112][113][114].…”

mentioning

confidence: 95%

“…Importantly, we show that including only the few flat bands is not sufficient but one needs also a number of dispersive bands to correctly predict the geometric contribution. Therefore, approximate models of TBG such as those with only flat bands, as used for deriving upper [29] and lower [30] bounds of the superfluid weight and in many other works [31][32][33][34][35][36][37][38][39][40][41][42][43], may not be suited for quantitative predictions of TBG superconductivity. Moreover, we predict that, in the flat-band regime, local (s-wave) and non-local interactions yield distinct behavior, namely an anisotropic superfluid weight in the latter case.…”

mentioning

confidence: 99%

“…An outstanding problem in describing the TBG physics theoretically [31][32][33][34][35][36][37][38][39][40][41][42][44][45][46][47][48][49][50][51][52][53][54][55][56][57][58][59][60] is the fact that the unit cell of the moiré superlattice with twist angles close to θ * contains a large amount of carbon atoms [ Fig. 1(a)], and therefore TBG theory should take a stand on how to describe the interlayer couplings within this unit cell.…”

mentioning

confidence: 99%

See 3 more Smart Citations

Superfluid weight and Berezinskii-Kosterlitz-Thouless transition temperature of twisted bilayer graphene

et al. 2020

View full text Add to dashboard Cite

We study superconductivity of twisted bilayer graphene with local and non-local attractive interactions. We obtain the superfluid weight and Berezinskii-Kosterlitz-Thouless (BKT) transition temperature for microscopic tight-binding and low-energy continuum models. We predict qualitative differences between local and non-local interaction schemes which could be distinguished experimentally. In the flat band limit where the pair potential exceeds the band width we show that the superfluid weight and BKT temperature are determined by multiband processes and quantum geometry of the band.Recent experimental discoveries of superconductivity in bilayer graphene twisted close to a "magic angle" θ * [1-3] call for a reconsideration of traditional theories of superconductivity [4, 5], in particular because the superconductivity occurs in a regime where the non-interacting electronic states form an asymptotically flat (dispersionless) band [6][7][8][9][10][11][12][13][14][15][16][17]. As the system is two-dimensional, the transition to superconductivity is bound to occur at the Berezinskii-Kosterlitz-Thouless (BKT) temperature T BKT [18][19][20] which can be determined from k B T BKT = π 8 arXiv:1906.06313v3 [cond-mat.mes-hall]

show abstract

supporting

confidence: 88%

mentioning

confidence: 95%

mentioning

confidence: 99%

mentioning

confidence: 99%

See 2 more Smart Citations

Superfluid weight and Berezinskii-Kosterlitz-Thouless transition temperature of twisted bilayer graphene

et al. 2020

View full text Add to dashboard Cite

show abstract

“…The described ladder formulation of the spin-fermion model was recently used to compute the antinodal contrib utions to the optical conductivity, σ(ω, T), as a function of frequency ω and temperature T (Classen et al 2019). The calcul ation made use of the memory function formalism, which was first applied to Luttinger liquids with umklapp scattering by Giamarchi (1991).…”

Section: Mapping Between the Spin-fermion Model And Twoleg Laddersmentioning

confidence: 99%

Anomalies in the pseudogap phase of the cuprates: competing ground states and the role of umklapp scattering

et al. 2019

View full text Add to dashboard Cite

Over the past two decades, advances in computational algorithms have revealed a curious property of the two-dimensional Hubbard model (and related theories) with hole doping: the presence of close-in-energy competing ground states that display very different physical properties. On the one hand, there is a complicated state exhibiting intertwined spin, charge, and pair density wave orders. We call this 'type A'. On the other hand, there is a uniform d-wave superconducting state that we denote as 'type B'. We advocate, with the support of both microscopic theoretical calculations and experimental data, dividing the high-temperature cuprate superconductors into two corresponding families, whose properties reflect either the type A or type B ground states at low temperatures. We review the anomalous properties of the pseudogap phase that led us to this picture, and present a modern perspective on the role that umklapp scattering plays in these phenomena in the type B materials. This reflects a consistent framework that has emerged over the last decade, in which Mott correlations at weak coupling drive the formation of the pseudogap. We discuss this development, recent theory and experiments, and open issues. * If one did not refermionise the spin sector, the non-linear interaction term within the bosonic theory reads −4g a =b cos Θ a cos Θ b , which is suggestive of a high symmetry. * This is easy to see in the purely bosonic language, as the interaction term −4g cos Θ sf cos Θ f at strong coupling pins the bosons to (Θ sf , Θ f ) = (2mπ, 2nπ or (Θ sf , Θ f ) = [2m + 1]π, [2n + 1]π with n, m ∈ Z. * Interestingly, recent gauge theory calculations that are proposed to apply to the pseudogap phase of the cuprates find such a deformation of the Fermi surface. See figure 7(a) of (Sachdev et al. 2018).

show abstract