Publications by authors named "D Calugaru"
Article Synopsis
- Flat bands can lead to unique physical properties like superconductivity and many-body effects, and their behavior depends on the quantum metric, which helps distinguish between interesting correlated physics and less significant dangling bonds.
- Geometric structures, such as the kagome lattice, show promise for creating correlated flat bands, though real materials often add complexity, making quantum geometry crucial for understanding band properties.
- Researchers used a soft-chemical process to oxidize Ni-kagome material CsNiS, significantly reducing its resistance, yet it remained insulating without any phase transition, hinting at a mysterious correlated insulating state.
We use the topological heavy fermion (THF) model and its Kondo lattice (KL) formulation to study the possibility of a symmetric Kondo (SK) state in twisted bilayer graphene. Via a large-N approximation, we find a SK state in the KL model at fillings ν=0,±1,±2 where a KL model can be constructed. In the SK state, all symmetries are preserved and the local moments are Kondo screened by the conduction electrons.
View Article and Find Full Text PDFGeometrically frustrated kagome lattices are raising as novel platforms to engineer correlated topological electron flat bands that are prominent to electronic instabilities. Here, we demonstrate a phonon softening at the k = π plane in ScVSn. The low energy longitudinal phonon collapses at ~98 K and q = [Formula: see text] due to the electron-phonon interaction, without the emergence of long-range charge order which sets in at a different propagation vector q = [Formula: see text].
View Article and Find Full Text PDFInteractions among electrons create novel many-body quantum phases of matter with wavefunctions that reflect electronic correlation effects, broken symmetries and collective excitations. Many quantum phases have been discovered in magic-angle twisted bilayer graphene (MATBG), including correlated insulating, unconventional superconducting and magnetic topological phases. The lack of microscopic information of possible broken symmetries has hampered our understanding of these phases.
View Article and Find Full Text PDFWe analytically compute the scanning tunneling microscopy (STM) signatures of integer-filled correlated ground states of the magic angle twisted bilayer graphene (TBG) narrow bands. After experimentally validating the strong-coupling approach at ±4 electrons/moiré unit cell, we consider the spatial features of the STM signal for 14 different many-body correlated states and assess the possibility of Kekulé distortion (KD) emerging at the graphene lattice scale. Remarkably, we find that coupling the two opposite graphene valleys in the intervalley-coherent (IVC) TBG insulators does not always result in KD.
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