arXiv subjects

Krisztián Márity

Publications and source records attributed to Krisztián Márity.

4 recordsLinked to original sources

arXiv2026

One-way electron mirrors from single-layer stacking shifts in rhombohedral graphite

One-way mirrors or asymmetric scatterers are key components of photonic systems, protecting sources from back-reflections and routing light along a chosen path. Acoustic systems can also be engineered to show asymmetric reflection. However, a condensed matter platform acting as a one-way mirror without breaking linearity, time-reversal symmetry or energy conservation has been lacking. One route to achieving this is mode selection, where a probe coupled to only some modes sees a boundary as a mirror from one side and as transparent from the other. Here we show that single-layer stacking shifts in six-layer rhombohedral graphite provide this platform, acting as one-way mirrors for electrons. In scanning tunneling microscopy, 10 nm scale interference fringes appear only on the stacking fault side of a wall, tracking its Dirac band, the rhombohedral side remaining transparent. Layer-resolved tight-binding and wave-packet dynamics calculations reproduce this and trace the asymmetry to the mismatched layer polarization across the wall, with the tip supplying the selective coupling. Because stacking solitons glide under external fields, this mirror forms a movable element of electron optics defined by the crystal structure alone.

cond-mat.mes-hall↗

arXiv2026

Enrichment of rhombohedral stacking by mechanical exfoliation of graphite

Rhombohedral (ABC) graphite hosts a surface-localized flat band that supports correlated and topological electronic phases, but its experimental study is limited by the scarcity of ABC stacking in natural graphite, which is dominated by Bernal (AB) stacking. Here we show that the routine mechanical exfoliation step itself enriches the rhombohedral content of graphite flakes, and that a simple blade-assisted exfoliation step, which introduces additional shear, amplifies the effect further. Using large-area Raman 2D-band skewness mapping we measure ABC content at area fractions of 3\% in the pristine source crystal, 16\% after conventional exfoliation, and 26\% after blade-assisted exfoliation for thick flakes. In thin flakes ($<20$ layers) the per-flake area fraction reaches 75\% in the upper tail of the distribution. Tracking individual flakes before and after blade-assisted exfoliation shows that wrinkles seed AB-ABC domain walls, and uniaxial strain can move these walls. Blade-assisted mechanical exfoliation therefore removes one of the bottlenecks to the preparation of ABC-rich graphite samples for studies of correlated and topological phases in rhombohedral graphite.

cond-mat.mtrl-sci↗

arXiv2026

Identification of graphite with perfect rhombohedral stacking by electronic Raman scattering

Rhombohedral graphite (RG) shows strong correlations in its topological flat band and is pivotal for exploring emergent, correlated electronic phenomena. One key advantage is the enhancement of electronic interactions with the increase in the number of rhombohedrally stacked graphene layers. Increasing thickness also leads to an exponential increase in the number of stacking faults, necessitating a precise method to identify flawless rhombohedral stacking. Overcoming this challenge is difficult because the established technique for stacking sequence identification, based on the Raman 2D peak, fails in thick RG samples. We demonstrate that the strong layer dependence of the band structure can be harnessed to identify RG without stacking faults, or alternatively, to detect their presence. For thicknesses ranging from 3 to 12 layers, we show that each perfect RG structure presents distinctive peak positions in electronic Raman scattering (ERS). This measurement can be carried out using a conventional confocal Raman spectrometer at room temperature, using visible excitation wavelengths. Consequently, this overcomes the identification challenge by providing a simple and fast optical measurement technique, thereby helping to establish RG as a platform for studying strong correlations in one of the simplest crystals possible.

cond-mat.mes-hall↗

arXiv2022

Observation of competing, correlated ground states in the flat band of rhombohedral graphite

In crystalline solids the interactions of charge and spin can result in a variety of emergent quantum ground states, especially in partially filled, topological flat bands such as Landau levels or in 'magic-angle' bilayer graphene. Much less explored is rhombohedral graphite (RG), perhaps the simplest and structurally most perfect condensed matter system to host a flat band protected by symmetry. By scanning tunneling microscopy we map the flat band charge density of 8, 10 and 17 layers and identify a domain structure emerging from a competition between a sublattice antiferromagnetic insulator and a gapless correlated paramagnet. Our density-matrix renormalization group calculations explain the observed features and demonstrate that the correlations are fundamentally different from graphene based magnetism identified until now, forming the ground state of a quantum magnet. Our work establishes RG as a new platform to study many-body interactions beyond the mean-field approach, where quantum fluctuations and entanglement dominate.

cond-mat.mes-hall↗