arXiv subjects

Bartłomiej Rzeszotarski

Publications and source records attributed to Bartłomiej Rzeszotarski.

5 recordsLinked to original sources

arXiv2024

Tuning topological superconductivity within the $t$-$J$-$U$ model of twisted bilayer cuprates

We carry out a theoretical study of unconventional superconductivity in twisted bilayer cuprates (TBC) as a function of electron density and layer twist angle. The bilayer $t$-$J$-$U$ model is employed and analyzed within the framework of a generalized variational wave function approach in the statistically-consistent Gutzwiller formulation. The constructed phase diagram encompasses both gapless $d$-wave state (reflecting the pairing symmetry of untwisted copper-oxides) and gapped $d+\mathrm{e}^{iφ}d$ phase that breaks spontaneously time-reversal-symmetry (TRS) and is characterized by nontrivial Chern number. We find that $d+\mathrm{e}^{iφ}d$ state occupies a non-convex butterfly-shaped region in the doping vs. twist-angle plane, and demonstrate the presence of previously unreported reentrant TRS-breaking phase on the underdoped side of the phase diagram. This circumstance supports the emergence of topological superconductivity for fine-tuned twist angles in TBC away from $45^\circ$. Our analysis of the microscopically derived Landau free energy functional points toward sensitivity of the superconducting order parameter to small perturbations close to the topological state boundary.

cond-mat.supr-con↗

arXiv2021

Effective Landé factors for an electrostatically defined quantum point contact in silicene

The transconductance and effective Landé $g^*$ factors for a quantum point contact defined in silicene by the electric field of a split gate is investigated. The strong spin-orbit coupling in buckled silicene reduces the $g^*$ factor for in-plane magnetic field from the nominal value 2 to around 1.2 for the first- to 0.45 for the third conduction subband. However, for perpendicular magnetic field we observe an enhancement of $g^*$ factors for the first subband to 5.8 in nanoribbon with zigzag and to 2.5 with armchair edge. The main contribution to the Zeeman splitting comes from the intrinsic spin-orbit coupling defined by the Kane-Mele form of interaction.

cond-mat.mes-hall↗

arXiv2020

Aharonov-Bohm oscillations of four-probe resistance in topological quantum rings in silicene and bilayer graphene

We consider observation of Aharonov-Bohm oscillations in clean systems based on the flow of topologically protected currents in silicene and bilayer graphene. The chiral channels in these materials are defined by the flips of the vertical electric field. The line of the flip confines chiral currents flowing along it in the direction determined by the valley. We present an electric field profile that forms a crossed ring to which four terminals can be attached, and find that the conductance matrix elements oscillate in the perpendicular magnetic field in spite of the absence of backscattering. We propose a four-probe resistance measurement setup, and demonstrate that the resistance oscillations have large visibility provided that the system is prepared in such a way that a direct transfer of the chiral carriers between the current probes is forbidden.

cond-mat.mes-hall↗

arXiv2019

Electron interferometry and quantum spin Hall phase in silicene

We discuss devices for detection of the topological insulator phase based on the two-path electron interference. For that purpose we consider buckled silicene for which a local energy gap can be opened by vertical electric field to close one of the paths and for which the quantum spin Hall insulator conditions are controlled by the Fermi energy. In quantum spin Hall phase the interference is absent due to the separation of the spin currents and the conductance of the devices include sharp features related to localized resonances. In the normal transport conditions the two-path interference produces a regular Aharonov-Bohm oscillations in the external magnetic field.

cond-mat.mes-hall↗

arXiv2018

Electron spin inversion in gated silicene nanoribbons

We study locally gated silicene nanoribbons as spin active devices. We find that the gated segments of nanoribbons with zigzag edge can be used to perform a spin inversion for the electron spins injected with an in-plane orientation. The strong intrinsic spin-orbit coupling for low Fermi energy in presence of an external vertical electric field provides a fast spin precession around the axis perpendicular to the silicene plane. The spin inversion length can be as small as 10 nm. On the other hand in the armchair nanoribbons the spin inversion occurs via the Rashba effect which is weak and the spin inversion lengths are of the order of $μ$m.

cond-mat.mes-hall↗