Publications

Order by: publication date number of citations

• Exact diagonalization, matrix product states and conformal perturbation theory study of a 3D Ising fuzzy sphere model

  Andreas M. Läuchli, Loïc Herviou, Patrick H. Wilhelm, Slava Rychkov

  SciPost Phys. 19, 076 (2025) · published 26 September 2025 | Toggle abstract · pdf

  Numerical studies of phase transitions in statistical and quantum lattice models provide crucial insights into the corresponding Conformal Field Theories (CFTs). In higher dimensions, comparing finite-volume numerical results to infinite-volume CFT data is facilitated by choosing the sphere $S^{d-1}$ as the spatial manifold. Recently, the fuzzy sphere regulator [Zhu et al, Phys. Rev. X 13, 021009 (2023)] has enabled such studies with exact rotational invariance, yielding impressive agreement with known 3D Ising CFT predictions, as well as new results. However, systematic improvements and a deeper understanding of finite-size corrections remain essential. In this work, we revisit the fuzzy sphere regulator, focusing on the original Ising model, with two main goals. First, we assess the robustness of this approach using Conformal Perturbation Theory (CPT), to which we provide a detailed guidebook. We demonstrate how CPT provides a unified framework for determining the critical point, the speed of light, and residual deviations from CFT predictions. Applying this framework, we study finite-size corrections and clarify the role of tuning the model in minimizing these effects. Second, we develop a novel method for extracting Operator Product Expansion (OPE) coefficients from fuzzy sphere data. This method leverages the sensitivity of energy levels to detuning from criticality, providing new insights into level mixing and avoided crossings in finite systems. Our work also includes validation of CPT in a 1+1D Ising model away from the integrable limit.

  2 citations

• Noninvertible symmetry and topological holography for modulated SPT in one dimension

  Jintae Kim, Yizhi You, Jung Hoon Han

  SciPost Phys. 19, 110 (2025) · published 24 October 2025 | Toggle abstract · pdf

  We examine noninvertible symmetry (NIS) in one-dimensional (1D) symmetry-protected topological (SPT) phases protected by dipolar and exponential-charge symmetries, which are two key examples of modulated SPT (MSPT). To set the stage, we first study NIS in the $\mathbb{Z}_N × \mathbb{Z}_N$ cluster model, extending previous work on the $\mathbb{Z}_2 × \mathbb{Z}_2$ case. For each symmetry type (charge, dipole, exponential), we explicitly construct the noninvertible Kramers-Wannier (KW) and Kennedy-Tasaki (KT) transformations, revealing dual models with spontaneous symmetry breaking (SSB). The resulting symmetry group structure of the SSB model is rich enough that it allows the identification of other SSB models with the same symmetry. Using these alternative SSB models and KT duality, we generate novel MSPT phases distinct from those associated with the standard decorated domain wall picture, and confirm their distinctiveness by projective symmetry analyses at their interfaces. Additionally, we establish a topological-holographic correspondence by identifying the 2D bulk theories-two coupled layers of toric codes (charge), anisotropic dipolar toric codes (dipole), and exponentially modulated toric codes (exponential)-whose boundaries host the respective 1D MSPT phases.

  2 citations

• Analysis of radiation damage in silicon charge-coupled devices used for dark matter searches

  Steven J. Lee

  SciPost Phys. Proc. 12, 030 (2023) · published 4 July 2023 | Toggle abstract · pdf

  Nuclear recoils in crystal detectors generate radiation damage in the form of crystal defects that can be measured in scientific-grade CCDs as local hot spots of leakage current stimulated by temperature increases in the devices. In this proceeding, we use a neutron source to generate defects in DAMIC-M CCDs, and using increases in leakage current at different temperatures, we demonstrate a procedure for identifying crystal defects in the CCDs of the DAMIC-M experiment. This is the first time that individual defects generated from nuclear recoils have been studied. This technique could be used to distinguish nuclear recoils from electron recoils in some energy ranges, which would improve the ability of CCD detectors to search for weakly interacting dark matter.

  2 citations

• Carlo.jl: A general framework for Monte Carlo simulations in Julia

  Lukas Weber

  SciPost Phys. Codebases 49 (2025) · published 7 February 2025 | Toggle abstract · pdf

  Carlo.jl is a Monte Carlo simulation framework written in Julia. It provides MPI-parallel scheduling (including parallel tempering), organized storage of input, checkpoint, and output files, as well as statistical postprocessing. With a minimalist design, it aims to aid the development of high-quality Monte Carlo codes, especially for demanding applications in condensed matter and statistical physics. This hands-on user guide shows how to implement a simple code with Carlo.jl, how to run an existing stochastic series expansion code based on Carlo.jl, and provides benchmarks to show its efficacy.

  2 citations

• Spectral properties, localization transition and multifractal eigenvectors of the Laplacian on heterogeneous networks

  Jeferson D. da Silva, Diego Tapias, Peter Sollich, Fernando L. Metz

  SciPost Phys. 18, 047 (2025) · published 7 February 2025 | Toggle abstract · pdf

  We study the spectral properties and eigenvector statistics of the Laplacian on highly-connected networks with random coupling strengths and a gamma distribution of rescaled degrees. The spectral density, the distribution of the local density of states, the singularity spectrum and the multifractal exponents of this model exhibit a rich behaviour as a function of the first two moments of the coupling strengths and the variance of the rescaled degrees. In the case of random coupling strengths, the spectral density diverges within the bulk of the spectrum when degree fluctuations are strong enough. The emergence of this singular behaviour marks a transition from non-ergodic delocalized states to localized eigenvectors that exhibit pronounced multifractal scaling. For constant coupling strengths, the bulk of the spectrum is characterized by a regular spectral density. In this case, the corresponding eigenvectors display localization properties reminiscent of the critical point of the Anderson localization transition on random graphs.

  2 citations

• Fermi-liquid corrections to the intrinsic anomalous Hall conductivity of topological metals

  Ivan Pasqua, Michele Fabrizio

  SciPost Phys. 19, 014 (2025) · published 16 July 2025 | Toggle abstract · pdf

  We show that topological metals lacking time-reversal symmetry have an intrinsic non-quantised component of the anomalous Hall conductivity which is contributed not only by the Berry phase of quasiparticles on the Fermi surface, but also by Fermi-liquid corrections due to the residual interactions among quasiparticles, the Landau $f$-parameters. These corrections pair up with those that modify the optical mass with respect to the quasiparticle effective one, or the charge compressibility with respect to the quasiparticle density of states. Our result supports recent claims that the correct expressions for topological observables include vertex corrections besides the topological invariants built just upon the Green's functions. Furthermore, it demonstrates that such corrections are naturally accounted for by Landau's Fermi liquid theory, here extended to the case in which coherence effects between bands crossing the chemical potential and those that are instead away from it may play a crucial role, as in the anomalous Hall conductivity, and have important implications when those metals are on the verge of a doping-driven Mott transition, as we discuss.

  2 citations

• Bilateral photon emission from a vibrating mirror and multiphoton entanglement generation

  Alberto Mercurio, Enrico Russo, Fabio Mauceri, Salvatore Savasta, Franco Nori, Vincenzo Macrì, Rosario Lo Franco

  SciPost Phys. 18, 067 (2025) · published 24 February 2025 | Toggle abstract · pdf

  Entanglement plays a crucial role in the development of quantum-enabled devices. One significant objective is the deterministic creation and distribution of entangled states, achieved, for example, through a mechanical oscillator interacting with confined electromagnetic fields. In this study, we explore a cavity resonator containing a two-sided perfect mirror. Although the mirror separates the cavity modes into two independent confined electromagnetic fields, the radiation pressure interaction gives rise to high-order effective interactions across all subsystems. Depending on the chosen resonant conditions, which are also related to the position of the mirror, we study $2n$-photon entanglement generation and bilateral photon pair emission. Demonstrating the non-classical nature of the mechanical oscillator, we provide a pathway to control these phenomena, opening potential applications in quantum technologies. Looking ahead, similar integrated devices could be used to entangle subsystems across vastly different energy scales, such as microwave and optical photons.

  2 citations

• Investigation of role of antisite disorder in pristine cage compound FeGa$_3$

  C. Kaufmann Ribeiro , L. Mello , V. Martelli , D. Cornejo, M. B. Silva Neto , E. Fogh , H. M. Rønnow, J. Larrea Jiménez

  SciPost Phys. Proc. 11, 023 (2023) · published 5 September 2023 | Toggle abstract · pdf

  The role of controlled Fe antisite disorder in the narrow gap semiconductor FeGa$_3$ has been investigated. Polycrystalline samples were synthesized by the combination of arc-melting furnace and successive annealing processes. Deviations from occupation numbers of Fe and Ga sites expected in the pristine compound were obtained from X-ray data using Rietveld refinement analysis. Besides that, electrical transport and magnetization measurements reveal that hierarchy in Fe and Ga site disorder tunes the ground state of FeGa$_3$ from paramagnetic semiconductor to a magnetic metal. These findings are discussed inside the framework of Anderson localization in the vicinity of metal-semiconductor transitions and spin fluctuations.

  2 citations

• Manifold curvature and Ehrenfest forces with a moving basis

  Jessica F. K. Halliday, Emilio Artacho

  SciPost Phys. 12, 020 (2022) · published 13 January 2022 | Toggle abstract · pdf

  Known force terms arising in the Ehrenfest dynamics of quantum electrons and classical nuclei, due to a moving basis set for the former, can be understood in terms of the curvature of the manifold hosting the quantum states of the electronic subsystem. Namely, the velocity-dependent terms appearing in the Ehrenfest forces on the nuclei acquire a geometrical meaning in terms of the intrinsic curvature of the manifold, while Pulay terms relate to its extrinsic curvature.

  2 citations

• Structural and magnetic anisotropy in YBa$_2$Cu$_3$O$_7$/La$_{0.67}$Sr$_{0.33}$MnO$_3$ bilayer on SrTiO$_3$ substrate

  Ankita Singh, Ram Prakash Pandeya, Sawani Dutta, Srinivas C. Kandukuri, Kalobaran Maiti

  SciPost Phys. Proc. 11, 007 (2023) · published 5 June 2023 | Toggle abstract · pdf

  We study the magnetic properties and emergence of superconductivity in YBa$_2$Cu$_3$O$_7$ (YBCO)/ La$_{0.67}$Sr$_{0.33}$MnO$_3$ (LSMO) heterostructures. Bilayer films of superconducting layer, YBCO, and ferromagnetic layer, LSMO were grown on SrTiO$_{3}$ (STO) (001) substrate using ultrahigh vacuum Pulsed Laser Deposition system. Magnetization data at 100 K as a function of applied magnetic field shows ferromagnetic behaviour due to the LSMO layer. Cooling below 100 K leads to superconductivity in this material; the onset of superconductivity occurs at a temperature, $T_{c,SC},$ of 86 K for $H_{ext}\perp c$ (in-plane) \& 84 K for $H_{ext}||c$ (out-of-plane) under 100 Oe applied field. In-plane magnetic measurements show significant suppression of diamagnetic behaviour as compared to the out-of-plane measurements. The susceptibility signals are higher for out-of-plane direction. Such strong anisotropy in magnetism and the transition temperatures reveal complex interplay of magnetism and superconductivity in this system and calls for further study in this direction.

  2 citations