arXiv subjects

Pavel A. Nosov

Publications and source records attributed to Pavel A. Nosov.

8 recordsLinked to original sources

arXiv2026

Lattice composite Fermi liquid with broken inversion symmetry

We study transport in lattice composite Fermi liquids realized in half-filled Chern bands with broken inversion symmetry. We show that reduced crystalline symmetry exposes intrinsic singular dynamical responses of composite fermions that are otherwise hidden in the conventional Landau-level setting. At zero wave vector, inversion breaking allows gauge-field fluctuations to generate a non-analytic longitudinal optical resistivity, with $\operatorname{Re}ρ^{xx}(ω)\sim |ω|^{4/3}$ for gate-screened Coulomb interactions. At finite wave vector $\mathbf{q}$, inversion breaking leads to nonreciprocal transport and a non-analytic $\sim |\mathbf{q}|$ dependence of the Hall conductivity, both of which can be probed through surface acoustic wave propagation. We also discuss a distinct mechanism for singular DC transport in lattice composite Fermi liquids: renormalization of $2k_F$ scattering at the composite Fermi surface enhances Umklapp relaxation and can lead to a non-analytic temperature dependence of the resistivity. Taken together, our results identify transport signatures of lattice composite Fermi liquids that are absent in their continuum quantum Hall counterparts and can be directly tested in ongoing experiments on twisted MoTe$_2$ and rhombohedral graphene, where evidence for zero-field composite Fermi liquids has recently been reported.

cond-mat.str-el↗

arXiv2026

Influence of Harris disorder on quantum-critical superconductivity

In the Hertz theory, a quantum critical metal is described by the coupling of a Fermi surface to fluctuations of a Landau-damped bosonic field $ϕ$, which may represent either an order parameter or a Higgs field for a transition without symmetry breaking. Scattering from $ϕ$ produces non-Fermi-liquid behavior in the normal state, while the same fluctuations mediate enhanced Cooper pairing. By the Harris criterion, symmetry-preserving disorder couples most strongly to the coefficient of the $ϕ^2$ term, locally tuning the system toward or away from criticality. This random mass (``Harris disorder'') leads to a finite density of localized low-energy $ϕ$ modes even when the fermionic states remain extended and continue to provide Landau damping. We study the onset of pairing mediated by these localized overdamped bosonic modes. Starting from a real-space linearized Usadel equation for the two-particle propagator, we show that the localized bosonic wave functions generate both a spatially random pairing vertex and an effective random potential for Cooper pairs. Numerical solution, a self-consistent Born approximation, and Lifshitz-tail analysis reveal two regimes of the pairing instability. At high temperatures, pairing nucleates compact superconducting puddles on the most localized bosonic modes. At lower temperatures, an extended pairing eigenstate appears, but its transition scale and spatial structure remain strongly affected by mesoscopic correlation effects and enhanced probability of returns to favorable regions of the localized bosonic glue. The resulting distribution of local pairing scales has a power-law tail, in contrast to the stretched-exponential tails of disordered BCS superconductors. This mechanism provides a route to broad gap inhomogeneity and superconducting puddles in quantum-critical metals, and offers an interpretation of STM measurements of the cuprates.

cond-mat.supr-con↗

arXiv2026

Bound states of anyons: a geometric quantization approach

The question of anyon interactions and their possible binding plays a key role in the physics of fractional quantum Hall states. Here, we introduce a controlled and scalable approach to study anyon binding by working entirely within the Hilbert space of anyons. The resulting theory is characterized by an effective potential, which captures the electrostatic energy of classical anyon configurations, and a Kähler potential, which simultaneously encodes the anyon Berry phase and the structure of their Hilbert space; both quantities are readily computed using Monte Carlo methods for large systems, enabling reliable extrapolation to the thermodynamic limit. By applying the formalism of geometric quantization on Kähler manifolds, we construct the anyon Hamiltonian, which can be exactly diagonalized in the few-anyon Hilbert space. Applying our approach to the quasiholes of the $ν=1/3$ Laughlin state with screened Coulomb interaction, we find that Laughlin quasiholes form bound states for screening lengths comparable or smaller than the magnetic length. Remarkably, binding occurs despite both the bare electron-electron interaction and the quasihole electrostatic potential being purely repulsive. The bound-state formation is a Berry phase effect, driven by oscillations in the quasihole density profile on the $\ell_B$ scale that are invisible in the quasihole electrostatic potential alone. For multiple quasiholes, we identify a sequence of phases as the screening length is reduced: free $e/3$ anyons, paired $2e/3$ bound states, three-anyon charge-$e$ clusters, and larger composite objects. Finally, we discuss possible signatures in charge imaging experiments on quantum Hall systems and the relevance to the phase diagram of itinerant anyon phases in fractional quantum anomalous Hall materials.

cond-mat.str-el↗

arXiv2026

Sondheimer magneto-oscillations as a probe of Fermi surface reconstruction in underdoped cuprates

Determining the Fermi surface (FS) volume in underdoped cuprates is crucial for understanding the nature of the strongly correlated pseudogap phase. Conventional quantum oscillation techniques, typically used for this purpose, are inapplicable in this high-temperature regime due to thermal and disorder-induced smearing of Landau levels. We propose Sondheimer oscillations (SO), semiclassical oscillations of in-plane magnetoresistivity in thin films, as a robust alternative probe of FS reconstruction. SO arise from the commensuration between the cyclotron radius and film thickness, do not rely on Landau quantization, and remain observable at moderate fields and elevated temperatures where quantum oscillations are suppressed. Their frequencies depend solely on the FS parameters (e.g., curvature), and not on specific details of scattering mechanisms. SO are also sensitive to the coherence of inter-layer tunneling, allow contributions from individual FS pockets to be distinguished in the frequency domain, and naturally include the Yamaji angle effect (if present in the system) as a prominent feature in the frequency spectrum. We compute SO spectra as a function of the magnetic field orientation for three representative scenarios: (i) an unreconstructed large FS, (ii) a spin density wave reconstructed FS with volume $p/4$, and (iii) a fractionalized Fermi liquid (FL$^*$) with pocket volume $p/8$ (here $p$ is the hole doping). We show that the SO spectrum offers a wealth of universal features that could be used to differentiate between these scenarios. In particular, we highlight a FS geometry-dependent phase shift between oscillations in longitudinal and transverse conductivities, characterize how the FS curvature can be extracted from SO if the film orientation is perpendicular to the crystallographic $c$-axis, and analyze the evolution of the SO spectrum with doping.

cond-mat.str-el↗

arXiv2026

Composite Bogoliubov Fermi liquid in a half-filled Chern band

The composite Fermi liquid (CFL) in the half-filled Landau level is a cornerstone of the quantum Hall phase diagram. Recent experiments and numerics indicate that an anomalous composite Fermi liquid (ACFL) can also arise at half filling of a Chern band without any external magnetic field, opening new possibilities for paired states of composite fermions beyond the fully gapped Pfaffian phase. We argue that in inversion-asymmetric Chern bands with lattice rotational symmetry reduced to $C_3$, as realized in experimental platforms where signatures of the ACFL have been observed, composite fermions can form a superconductor with neutral gapless Bogoliubov Fermi surfaces. We term the resulting electronic state {\it the composite Bogoliubov Fermi liquid (CBFL)}. This phase has a number of remarkable properties that make it distinct from both the ACFL and the fully gapped Pfaffian. For instance, it is incompressible, has quantized Hall conductance, shows no quantum oscillations as a function of magnetic field or doping, and has topological ground state degeneracy on a torus despite the presence of gapless quasiparticles. At the same time, the neutral Bogoliubov Fermi surface yields metallic $T$-linear specific heat, non-quantized thermal conductance, Landau damping of density fluctuations, and a non-analytic $|\mathbf{q}|^3$ contribution to the equal-time structure factor $S(\mathbf{q})$. We also briefly discuss vortex physics and possible fractionalized daughter states induced by doping or external magnetic fields. Our results pave the way for a broader understanding of gapless topological phases arising from paired composite fermions in Chern bands that go beyond the conventional Landau level paradigm.

cond-mat.str-el↗

arXiv2025

Anyon superconductivity and plateau transitions in doped fractional quantum anomalous Hall insulators

Recent experiments reported evidence of superconductivity and re-entrant integer quantum anomalous Hall (RIQAH) insulator upon doping the $ν_e = 2/3$ fractional quantum anomalous Hall states (FQAH) in twisted MoTe${}_2$, separated by narrow resistive regions. Anyons of a FQAH generally have a finite effective mass, and when described by anyon-flux composite fermions (CF), experience statistical magnetic fields with a commensurate filling. Here, we show that most of the experimental observations can be explained by invoking the effects of disorder on the Landau-Hofstadter bands of CFs. In particular, by making minimal assumptions about the anyon energetics and dispersion, we show that doping anyons drives plateau transitions of CFs into integer quantum Hall states, which physically corresponds to either to a superconductor or to a RIQAH phase. We develop a dictionary that allows us to infer the response in these phases and the critical regions from the knowledge of the response functions of the plateau transitions. In particular, this allows us to relate the superfluid stiffness of the superconductor to the polarizability of CFs. As a first step towards a quantitative understanding, we borrow results from the celebrated integer quantum Hall plateau transitions to make quantitative prediction for the critical behavior of the superfluid stiffness, longitudinal and Hall conductivity, and response to out-of-plane magnetic field, all of which agree reasonably well with the experimental observations. Our results provide strong support for anyon superconductivity being the mechanism for the observed superconductor in the vicinity of the $ν_e = 2/3$ FQAH insulator.

cond-mat.str-el↗

arXiv2025

Theory of Sondheimer magneto-oscillations beyond semiclassical limit

In conducting films subjected to an out-of-plane magnetic field, electron motion along the field direction gives rise to conductance oscillations periodic in field intensity - a phenomenon known as Sondheimer oscillations. Traditionally, these oscillations were understood within the semiclassical framework of kinetic theory. However, their behavior in the quantum regime (i.e. at strong fields and weak disorder) remains unclear, particularly due to potential interference with quantum Shubnikov-de Haas magneto-oscillations. In this work, we develop a comprehensive theory of quantum magnetoconductivity oscillations in metallic films of finite thickness, fully capturing the interplay between the Sondheimer and Shubnikov-de Haas effects beyond the semiclassical limit. By treating surface scattering, in-plane Landau quantization, and dimensional confinement along the magnetic field direction on equal footing, we reveal an intricate hierarchy of oscillation patterns and characterize how their amplitudes and frequencies depend on various physical parameters. Our results pave the way for systematic characterization of thin metallic films with boundary-dominated transport properties.

cond-mat.mes-hall↗

arXiv2025

Angular Interplay of Nematicity, Superconductivity, and Strange Metallicity in a Moiré Flat Band

Superconductivity in strongly correlated electron systems frequently exhibits broken rotational symmetry, raising fundamental questions about the underlying order parameter symmetry. In this work, we demonstrate that electronic nematicity--driven by Coulomb-mediated rotational symmetry breaking--serves as a crucial link to understanding the nature of superconductivity. Utilizing a novel framework of angle-resolved measurement, we reveal an interring angular interplay among nematicity, superconductivity, and strange metallicity in magic-angle twisted trilayer graphene. By establishing a direct correlation between the preferred superconducting transport direction and the principal axis of the metallic phase, our findings place strong constrains on the symmetry of the superconducting order parameter. This work introduces a new paradigm for probing the microscopic mechanisms governing superconductivity in strongly interacting two-dimensional systems.

cond-mat.mes-hall↗