arXiv subjects

Vladislav Poliakov

Publications and source records attributed to Vladislav Poliakov.

4 recordsLinked to original sources

arXiv2026

Tomographic imaging of superconducting order using particle-hole interference

Superconducting phases with exotic symmetries that differ from the underlying crystalline lattice are at the focus of superconductivity research. Yet, despite intense interest, detecting the order parameter symmetry and topology remains a major challenge. Real-space imaging near atomic impurities with scanning tunneling microscopy (STM) has been highly successful in revealing nodes of the superconducting gap, in particular in cuprate superconductors, however the order parameter phase winding has so far remained inaccessible by STM techniques. We demonstrate that STM can access this phase information by exploiting Young-type quasiparticle interference patterns generated by pairs of impurities acting as beam splitters. Superconducting order parameter tomography (SOPT), a technique proposed here, utilizes the response of real-space interference patterns of Bogoliubov quasiparticles to the controlled rotation of impurity configurations, allowing us to reconstruct the momentum space structure of the gap function $Δ(\vec{k})$. As a concrete example, we consider Strontium Ruthenate, whose superconducting order remains a subject of ongoing debate, and demonstrate how SOPT can distinguish between competing order parameter candidates. The Young's interference fringes, nodal directions, and rotating beams, detected by SOPT, encode information about both the nodes and phase winding of the superconducting order parameter. This method provides a broadly applicable route to identifying unconventional and topological superconductivity and establishes particle-hole interference as a new imaging modality for superconducting order.

cond-mat.supr-con↗

arXiv2026

Particle-Hole Ghost Interference in Superconductors

Mirror-assisted optical interference can improve the fidelity of Young's double-slit interference. Here we discuss an electron analogue: particle-hole interference in superconductors produced by a single impurity near a line defect, terrace edge, or phase boundary. Quasiparticle waves scattered directly from the impurity interfere with waves reflected by the boundary, generating a ``ghost'' interference pattern that combines conventional $2k_F$ Friedel oscillations with additional hyperbolic fringes. Compared to the recently studied two-impurity Young's interference, this effect appears already at first order in the impurity potential and is therefore parametrically stronger. The resulting spatial modulation extends beyond $λ_F/2$ and is directly sensitive to the quasiparticle structure of the paired state, including possible Fermi-surface anisotropy of the superconducting order parameter. These findings point to boundary-assisted impurity interference as a robust local probe of superconducting electronic order, with clear signatures accessible to STM/STS measurements.

cond-mat.supr-con↗

arXiv2024

Spin chirality and fermion stirring in topological bands

We demonstrate that in metals, both normal and superconducting, orbital currents present in the ground state when time reversal symmetry (TRS) is broken, generate spin chirality. Nonzero chirality can emerge in the absence of any spin-dependent interactions, even when the ground state remains spin-unpolarized. The chirality effect is derived diagrammatically and illustrated for Haldane model and the topological superconductivity problem. Chirality in the carrier band results in a chiral three-spin RKKY interaction between localized spins coupled to carriers by s-d Hamiltonian, an effect that can be detected by local probes such as spin-sensitive STM. In systems where detecting TRS breaking by conventional means is challenging, such as topological superconductors, local detection of spin chirality can serve as a reliable diagnostic of superconducting topological phases.

cond-mat.mes-hall↗

arXiv2024

Topological transitions in the Yao-Lee spin-orbital model and effects of site disorder

The Yao-Lee model is an example of exactly solvable spin-orbital models that are generalizations of the original Kitaev honeycomb model with extra local orbital degrees of freedom. Similar to the Kitaev model, both spin and orbital degrees of freedom are effectively represented using sets of three-flavored Majorana fermions. The Yao-Lee model exhibits a quantum spin liquid ground state with gapped and immobile $Z_2$ fluxes and three-fold degenerate itinerant Majorana fermions. Our work demonstrated that by introducing different time-reversal symmetry (TRS) breaking fields one can split the degeneracy of Majorana fermions and close the gap for some of the bands, thus changing its topology. We calculated a comprehensive topological phase diagram for the Yao-Lee model by considering various combinations of TRS-breaking fields. This investigation revealed the emergence of distinct topological regions, each separated by nodal lines, signifying an evolution in the model's topological properties. We also investigated the impact of vacancies in the system. Our findings revealed that while vacancies modify the low-energy spectrum of the model, their presence has a limited impact on the topological properties of the model, at least for small enough concentrations.

cond-mat.str-el↗