Electronic Raman Scattering in Twistronic Few-Layer Graphene

Optically-induced Umklapp shift currents in striped cuprates

“…On the theoretical front, it would be interesting to: i) establish whether the Umklapp shift current has a topological origin, as has been recently discussed in the context of the regular nonlinear probes [23]; ii) extend the presented framework to incorporate the effects of the static short-range disorder, as many strongly-correlated materials have substantial randomness; iii) include the effects of interactions beyond mean-field to understand the role of low-energy collective excitations better [24] ; and iv) generalize our modeling to include such phases as PDW states. On the experimental side, additional probes, such as Raman scattering [55][56][57][58] and near-field measurements [33], that might sense both shift currents are highly desirable, as they can help confirm our theoretical conclusions.…”

Moiré Superlattice Effects and Band Structure Evolution in Near-30-Degree Twisted Bilayer Graphene

“…In van der Waals heterostructures with twisted interfaces, two mechanisms are known to induce DoS peaks: (i) direct hybridization of states from different layers 15 and (ii) coupling between states backfolded by the mSL. 38 Both lead to opening of gaps in the electronic spectrum as a consequence of coupling between electronic states, accompanied by the appearance of saddle points in the dispersion which in turn are responsible for the DoS peaks. Therefore, to understand the energy distribution curves in Figure 3 a, we look for signs of minigap formation by investigating photoemission spectra along the k -space paths connecting the valleys K 1 , K 1 ′ , and K 2 as shown in Figure 1 a.…”

“…The neighboring Dirac points are separated by a distance ( 35 ) ( K 1 and K 2 as marked in Figure 1 ), where a is the graphene lattice constant, or ( K 2 and K 1 ′ ). The highest energies of crossings occur midway between every pair of Dirac points and the corresponding energies as a function of θ are indicated with the black dashed lines on top of the DoS curves in Figure 4 a. Interlayer coupling hybridizes the degenerate states at the crossings, turning them into anticrossings accompanied by a saddle point between the Dirac points and above the gap (note that the saddle point is shifted off the line connecting the Dirac points 38 ) and a quasi-quadratic edge of the next miniband below. The corresponding DoS features, peak at higher energies due to the saddle point, and a step at lower energies due to the band edge, can be seen in the vicinity of both dashed black lines in the DoS curves in panel a (the hybridization minigap does not open a global band gap as other parts of the electronic dispersion overlap with it so that the electronic density of states does not go down to zero 15 , 17 , 36 ).…”

Full Slonczewski-Weiss-McClure parametrization of few-layer twistronic graphene

“…4 (a) and (b), for θ = 2 • and θ = 1.1 • , respectively, in comparison with the minibands computed using the minimal model. The comparison of the two spectra shows that the influence of the additional terms, accounting for the full set of SWMcC couplings, is weak, suggesting that minimal model for the twisted interface coupling can be safely combined with the most detailed description of the Bernalstacking part of twistronic few-layer graphene for the analysis of flat bands in such systems 10,11,53 .…”