Publications Francesca FERLAINO

2025

Article

• E. Poli, A. Litvinov, E. Casotti, C. Ulm, L. Klaus, M. J. Mark, G. Lamporesi, T. Bland, F. Ferlaino Synchronization in rotating supersolids, Nature Phys. (2025-10-23), http://dx.doi.org/10.48550/arXiv.2412.11976 doi:10.48550/arXiv.2412.11976
  Synchronization is a widespread phenomenon in natural and engineered systems, governing the emergence of collective dynamics in different domains including biology and classical and quantum physics. In quantum many-body systems, synchronization has emerged as a tool to probe out-of-equilibrium behaviour and internal correlations. Supersolids—quantum phases that combine crystalline order and superfluidity—offer a platform to explore synchronization in systems with coexisting broken symmetries. Here we investigate the dynamics of a dipolar supersolid subjected to external rotation. We show that, above a critical driving frequency, the crystal revolution undergoes a sudden synchronization with the rotating field seeded by the nucleation of quantized vortices, hallmark of superfluidity. This transition reflects the interplay between the solid-like and superfluid responses of the system. By comparing simulations of the extended Gross–Pitaevskii equation with experimental observations, we demonstrate that synchronization can serve as a dynamical indicator for vortex nucleation. This approach provides a complementary method to determine the critical rotation frequency for vortex formation in supersolids.

Preprints

• L. Lafforgue, N. Mehta, J. J. Houwman, F. Claude, S. T. Rittenhouse, F. Ferlaino, M. J. Mark Observation of Fano-suppression in scattering resonances of bosonic erbium atoms, (2025-12-19),
  The collisional properties of lanthanides exhibit remarkable complexity due to their many valence electrons, leading to an extraordinarily dense Feshbach spectrum showing signs of quantum chaos. Here we explore the situation of bosonic spin mixtures of erbium, adding the additional spin degree of freedom to the problem. We detect several inter- and intra-spin scattering resonances, exhibiting a peculiar asymmetric shape with a pronounced loss minimum. By developing a simplified multi-channel model we are able to recreate this characteristic behavior and to trace its origin to destructive interference between multiple pathways as predicted by Fano. We additionally observe a series of Fano-Feshbach resonances across multiple spin channels connected to the same molecular state, again confirmed by our theory. Our work opens the door for a detailed investigation to study multi-spin strongly-coupled scattering phenomena.
• L. Bellinato Giacomelli, T. Bland, L. Lafforgue, F. Ferlaino, M. J. Mark, L. Barbiero Topology meets superconductivity in a one-dimensional t-J model of magnetic atoms, (2025-09-03), http://dx.doi.org/10.48550/arXiv.2509.03387 doi:10.48550/arXiv.2509.03387
  Strongly interacting fermions represent the key constituent of several intriguing phases of matter. However, due to the inherent complexity of these systems, important regimes are still inaccessible. Here, we derive a realistic and flexible setup based on ultracold magnetic lanthanide atoms trapped in a one-dimensional optical lattice. Leveraging their large magnetic moments, we design a fermionic t-J model with independently tunable hopping, spin-spin couplings, and onsite interaction. Through combined analytical and numerical analysis, we uncover a variety of many-body quantum phases including superconducting and topological states. Crucially, in the regime of attractive onsite interaction we reveal that topology and superconductivity coexist, thus giving rise to an exotic state of matter: a topological triplet superconductor. We also outline a practical protocol to prepare and detect all discovered phases using current experimental techniques. Our results establish an alternative and powerful route for a deeper understanding of strongly interacting fermionic quantum matter.
• D. Schneider Grün, L. Bellinato Giacomelli, A. Tashchilina, R. Donofrio, F. Borchers, T. Bland, M. J. Mark, F. Ferlaino Light-Assisted Collisions in Tweezer-Trapped Lanthanides, (2025-06-05), http://dx.doi.org/10.48550/arXiv.2506.05123 doi:10.48550/arXiv.2506.05123
  We present a quantitative investigation of one- and two-body light-mediated processes that occur to few erbium atoms in an optical tweezer, when exposed to near-resonant light. In order to study the intertwined effects of recoil heating, cooling and light-assisted collisions, we develop a first-principles Monte Carlo algorithm that solves the coupled dynamics of both the internal and external degrees of freedom of the atoms. After validating our theoretical model against experimental data, we use the predictive power of our code to guide our experiment and, in particular, we explore the performance of different transitions of erbium for light-assisted collisions in terms of their efficiency and fidelity for single-atom preparation.

2024

Articles

• D. Schneider Grün, S. White, A. Ortu, A. Di Carli, H. Edri, M. Lepers, M. J. Mark, F. Ferlaino Optical Tweezer Arrays of Erbium Atoms, Phys. Rev. Lett. 133 223402 (2024-11-26), http://dx.doi.org/10.1103/PhysRevLett.133.223402 doi:10.1103/PhysRevLett.133.223402
  We present the first successful trapping of single erbium atoms in an array of optical tweezers. Using a single narrow-line optical transition, we achieve deep cooling for direct tweezer loading, pairwise ejection, and continuous imaging without additional recoil suppression techniques. Our tweezer wavelength choice enables us to reach the magic trapping condition by tuning the ellipticity of the trapping light. Additionally, we implement an ultrafast high-fidelity fluorescence imaging scheme using a broad transition, allowing time-resolved study of the tweezer population dynamics from many to single atoms during light-assisted collisions. In particular, we extract a pair-ejection rate that qualitatively agrees with the semiclassical predictions by the Gallagher-Pritchard model. This Letter represents a promising starting point for the exploration of erbium as a powerful resource for quantum simulation in optical tweezers.
• E. Casotti, E. Poli, L. Klaus, A. Litvinov, C. Ulm, C. Politi, M. J. Mark, T. Bland, F. Ferlaino Observation of vortices in a dipolar supersolid, Nature 635 331 (2024-11-06), http://dx.doi.org/10.1038/s41586-024-08149-7 doi:10.1038/s41586-024-08149-7
  Supersolids are states of matter that spontaneously break two continuous symmetries: translational invariance owing to the appearance of a crystal structure and phase invariance owing to phase locking of single-particle wavefunctions, responsible for superfluid phenomena. Although originally predicted to be present in solid helium1,2,3,4,5, ultracold quantum gases provided a first platform to observe supersolids6,7,8,9,10, with particular success coming from dipolar atoms8,9,10,11,12. Phase locking in dipolar supersolids has been investigated through, for example, measurements of the phase coherence8,9,10 and gapless Goldstone modes13, but quantized vortices, a hydrodynamic fingerprint of superfluidity, have not yet been observed. Here, with the prerequisite pieces at our disposal, namely a method to generate vortices in dipolar gases14,15 and supersolids with two-dimensional crystalline order11,16,17, we report on the theoretical investigation and experimental observation of vortices in the supersolid phase (SSP). Our work reveals a fundamental difference in vortex seeding dynamics between unmodulated and modulated quantum fluids. This opens the door to study the hydrodynamic properties of exotic quantum systems with numerous spontaneously broken symmetries, in disparate domains such as quantum crystals and neutron stars18.
• E. Poli, D. Baillie, F. Ferlaino, B. Blakie Excitations of a two-dimensional supersolid, Phys. Rev. A 11o 53301 (2024-11-04), http://dx.doi.org/10.1103/PhysRevA.110.053301 doi:10.1103/PhysRevA.110.053301
  We present a theoretical study of the excitations of the two-dimensional supersolid state of a Bose-Einstein condensate with either dipole-dipole interactions or soft-core interactions. This supersolid state has three gapless excitation branches arising from the spontaneously broken continuous symmetries. Two of these branches are related to longitudinal sound waves, similar to those in one-dimensional supersolids. The third branch is a transverse wave arising from the nonzero shear modulus of the two-dimensional crystal. We present the results of numerical calculations for the excitations and dynamic structure factor characterizing the density fluctuations and study their behavior across the discontinuous superfluid to supersolid transition. We show that the speeds of sound are described by a hydrodynamic theory that incorporates generalized elastic parameters, including the shear modulus. Furthermore, we establish that dipolar and soft-core supersolids manifest distinct characteristics, falling into the bulk-incompressible and rigid-lattice limits, respectively.
• F. Claude, L. Lafforgue, A. Houwman, M. J. Mark, F. Ferlaino Optical Manipulation of spin states in ultracold magnetic atoms via an inner-shell hz transition, Phys. Rev. Research 6 L042016 (2024-10-18), http://dx.doi.org/10.1103/PhysRevResearch.6.L042016 doi:10.1103/PhysRevResearch.6.L042016
  Lanthanides, like erbium and dysprosium, have emerged as powerful platforms for quantum-gas research due to their diverse properties, including a significant large spin manifold in their absolute ground state. However, effectively exploiting the spin richness necessitates precise manipulation of spin populations, a challenge yet to be fully addressed in this class of atomic species. In this work, we present an all-optical method for deterministically controlling the spin composition of a dipolar bosonic erbium gas, based on a clocklike transition in the telecom window at 1299n⁢m. The atoms can be prepared in just a few tens of microseconds in any spin-state composition using a sequence of Rabi-pulse pairs, selectively coupling Zeeman sublevels of the ground state with those of the long-lived clocklike state. Finally, we demonstrate that this transition can also be used to create spin-selective light shifts, thus fully suppressing spin-exchange collisions. These experimental results unlock exciting possibilities for implementing advanced spin models in isolated, clean, and fully controllable lattice systems.
• E. Poli, T. Bland, M. J. Mark, M. Mannarelli, F. Ferlaino Quantenwirbel beschleunigen Neutronensterne, Spektrum der Wissenschaft (2024-09-27), URL
• W. Kirkby, A. Lee, D. Baillie, T. Bland, F. Ferlaino, B. Blakie, R. N. Bisset Excitations of a binary dipolar supersolid, Phys. Rev. Research 133 103401 (2024-09-04), http://dx.doi.org/10.1103/PhysRevLett.133.103401 doi:10.1103/PhysRevLett.133.103401
  We predict a rich excitation spectrum of a binary dipolar supersolid in a linear crystal geometry, where the ground state consists of two partially immiscible components with alternating, interlocking domains. We identify three Goldstone branches, each with first-sound, second-sound, or spin-sound character. In analogy with a diatomic crystal, the resulting lattice has a two-domain primitive basis and we find that the crystal (first-sound-like) branch is split into optical and acoustic phonons. We also find a spin-Higgs branch that is associated with the supersolid modulation amplitude.
• T. Bland, F. Ferlaino, M. Mannarelli, E. Poli, S. Trabucco Exploring Pulsar Glitches with Dipolar Supersolids, Few-Body Syst. 65 81 (2024-08-16), http://dx.doi.org/10.1007/s00601-024-01949-7 doi:10.1007/s00601-024-01949-7
  Glitches are sudden spin-up events that interrupt the gradual spin-down of rotating neutron stars. They are believed to arise from the rapid unpinning of vortices in the neutron star inner crust. The analogy between the inner crust of neutron stars and dipolar supersolids allows to investigate glitches. Employing such analogy, we numerically analyze the vortex trapping mechanism and how the matter density distribution influences glitches. These results pave the way for the quantum simulation of celestial bodies in laboratories.
• M. J. Mark, F. Ferlaino Der Suprafestkörper, Physik in unserer Zeit 55 241 (2024-04-05), http://dx.doi.org/10.1002/piuz.202301692 doi:10.1002/piuz.202301692
• J. Argüello-Luengo, M. J. Mark, F. Ferlaino, M. Lewenstein, L. Barbiero, S. Julià Farré Stabilization of Hubbard-Thouless pumps through nonlocal fermionic repulsion, Quantum 8 1285 (2024-03-14), http://dx.doi.org/10.22331/q-2024-03-14-1285 doi:10.22331/q-2024-03-14-1285
  Thouless pumping represents a powerful concept to probe quantized topological invariants in quantum systems. We explore this mechanism in a generalized Rice-Mele Fermi-Hubbard model characterized by the presence of competing onsite and intersite interactions. Contrary to recent experimental and theoretical results, showing a breakdown of quantized pumping induced by the onsite repulsion, we prove that sufficiently large intersite interactions allow for an interaction-induced recovery of Thouless pumps. Our analysis further reveals that the occurrence of stable topological transport at large interactions is connected to the presence of a spontaneous bond-order-wave in the ground-state phase diagram of the model. Finally, we discuss a concrete experimental setup based on ultracold magnetic atoms in an optical lattice to realize the newly introduced Thouless pump. Our results provide a new mechanism to stabilize Thouless pumps in interacting quantum systems.
• A. Houwman, D. Baillie, B. Blakie, G. Natale, F. Ferlaino, M. J. Mark Measurement of the excitation spectrum of a dipolar gas in the macrodroplet regime, Phys. Rev. Lett. 132 103401 (2024-03-07), http://dx.doi.org/10.1103/PhysRevLett.132.103401 doi:10.1103/PhysRevLett.132.103401
  The excitation spectrum of a cigar-shaped strongly dipolar quantum gas at the crossover from a Bose-Einstein condensate to a trapped macrodroplet is predicted to exhibit peculiar features - a strong upward shift of low momentum excitation energies together with a strong multi-band response for high momenta. By performing Bragg spectroscopy over a wide range of momenta, we observe both key elements and also confirm the predicted stiffening of excitation modes when approaching the macrodroplet regime. Our measurements are in good agreement with numerical calculations taking into account finite size effects.

Preprint

• E. Poli, A. Litvinov, E. Casotti, C. Ulm, L. Klaus, M. J. Mark, G. Lamporesi, T. Bland, F. Ferlaino Synchronization in rotating supersolids, (2024-12-16), http://dx.doi.org/10.48550/arXiv.2412.11976 doi:10.48550/arXiv.2412.11976
  Synchronization is ubiquitous in nature at various scales and fields. This phenomenon not only offers a window into the intrinsic harmony of complex systems, but also serves as a robust probe for many-body quantum systems. One such system is a supersolid: an exotic state that is simultaneously superfluid and solid. Here, we show that putting a supersolid under rotation leads to a synchronization of the crystal's motion to an external driving frequency triggered by quantum vortex nucleation, revealing the system's dual solid-superfluid response. Benchmarking the theoretical framework against experimental observations, we exploit this model as a novel method to investigate the critical frequency required for vortex nucleation. Our results underscore the utility of synchronization as a powerful probe for quantum systems.

2023

Articles

• W. Kirkby, A. Lee, D. Baillie, T. Bland, F. Ferlaino, B. Blakie, R. N. Bisset Excitations of a binary supersolid, Phys. Rev. Lett. 133 103401 (2023-12-06), http://dx.doi.org/10.1103/PhysRevLett.133.103401 doi:10.1103/PhysRevLett.133.103401
  We predict a rich excitation spectrum of a binary dipolar supersolid in a linear crystal geometry, where the ground state consists of two partially immiscible components with alternating, interlocking domains. We identify three Goldstone branches, each with first-sound, second-sound or spin-sound character. In analogy with a diatomic crystal, the resulting lattice has a two-domain primitive basis and we find that the crystal (first-sound-like) branch is split into optical and acoustic phonons. We also find a spin-Higgs branch that is associated with the supersolid modulation amplitude.
• W. Kirkby, T. Bland, F. Ferlaino, R. N. Bisset Spin rotons and supersolids in binary antidipolar condensates, SciPost Phys. 6 84 (2023-12-04), http://dx.doi.org/10.21468/SciPostPhysCore.6.4.084 doi:10.21468/SciPostPhysCore.6.4.084
  We present a theoretical study of a mixture of antidipolar and nondipolar Bose-Einstein condensates confined to an infinite tube. The long-ranged inverted dipolar interactions result in a spin roton instability associated with an unmodulated-to-supersolid phase transition. We present a phase diagram including unmodulated miscible, supersolid, incoherent domain, and macroscopic domain phases. The low densities of the binary mixture do not require beyond-mean-field quantum fluctuation corrections for stabilization. Our survey ranges from the quasi-1D to the radial Thomas-Fermi (elongated 3D) regimes. We also present the dynamic formation of supersolids following a quench from the uniform miscible phase, which maintains phase coherence across the system.
• E. Poli, T. Bland, S. White, M. J. Mark, F. Ferlaino, S. Trabucco, M. Mannarelli Glitches in rotating supersolids, PRL 131 223401 (2023-11-29), http://dx.doi.org/10.1103/PhysRevLett.131.223401 doi:10.1103/PhysRevLett.131.223401
  Glitches, spin-up events in neutron stars, are of prime interest as they reveal properties of nuclear matter at subnuclear densities. We numerically investigate the glitch mechanism using analogies between neutron stars and magnetic dipolar gases in the supersolid phase. In rotating neutron stars, glitches are believed to occur when many superfluid vortices unpin from the interior, transferring angular momentum to the stellar surface. In the supersolid analogy, we show that a glitch happens when vortices pinned in the low-density inter-droplet region abruptly unpin. These supersolid glitches show remarkable parallels with neutron star glitches: they are characterized by a rapid spin-up followed by a long post-glitch spin-down due to relaxation towards a steady state. Dipolar supersolids offer an unprecedented possibility to test both the vortex and crystal dynamics during a glitch. Here, we explore the glitch dependence on the supersolid quality, finding strong suppression at the supersolid-to-solid transition. This provides a tool to study glitches originating from different radial depths of a neutron star. Benchmarking our theory against neutron star observations, our work will open a new avenue for the quantum simulation of stellar objects from Earth.
• M. Sohmen, M. J. Mark, M. Greiner, F. Ferlaino A ship-in-a-bottle quantum gas microscope for magnetic mixtures., SciPost Phys. 15 182 (2023-11-01), http://dx.doi.org/10.21468/SciPostPhys.15.5.182 doi:10.21468/SciPostPhys.15.5.182
  Quantum gas microscopes are versatile and powerful tools for fundamental science as well as promising candidates for enticing applications such as in quantum simulation or quantum computation. Here we present a quantum gas microscopy setup for experiments with highly magnetic atoms of the lanthanoid elements erbium and dysprosium. Our setup features a non-magnetic, non-conducting, large-working-distance, high-numerical-aperture, in-vacuum microscope objective, mounted inside a glue-free quartz glass cell. The quartz glass cell is enclosed by a compact multi-shell ferromagnetic shield that passively suppresses external magnetic field noise by a factor of more than a thousand. Our setup will enable direct manipulation and probing of the rich quantum many-body physics of dipolar atoms in optical lattices, and bears the potential to put exciting theory proposals - including exotic magnetic phases and quantum phase transitions - to an experimental test.
• L. Su, A. Douglas, M. Szurek, R. Groth, F. Ozturk, A. Krahn, A. Hébert, G. Phelps, S. Ebadi, S. Dickerson, F. Ferlaino, O. Markovic, M. Greiner Dipolar quantum solids emerging in a Hubbard quantum simulator, Nature 622 729 (2023-10-25), http://dx.doi.org/10.1038/s41586-023-06614-3 doi:10.1038/s41586-023-06614-3
  In quantum mechanical many-body systems, long-range and anisotropic interactions promote rich spatial structure and can lead to quantum frustration, giving rise to a wealth of complex, strongly correlated quantum phases. Long-range interactions play an important role in nature; however, quantum simulations of lattice systems have largely not been able to realize such interactions. A wide range of efforts are underway to explore long-range interacting lattice systems using polar molecules, Rydberg atoms, optical cavities, and magnetic atoms. Here, we realize novel quantum phases in a strongly correlated lattice system with long-range dipolar interactions using ultracold magnetic erbium atoms. As we tune the dipolar interaction to be the dominant energy scale in our system, we observe quantum phase transitions from a superfluid into dipolar quantum solids, which we directly detect using quantum gas microscopy with accordion lattices. Controlling the interaction anisotropy by orienting the dipoles enables us to realize a variety of stripe ordered states. Furthermore, by transitioning non-adiabatically through the strongly correlated regime, we observe the emergence of a range of metastable stripe-ordered states. This work demonstrates that novel strongly correlated quantum phases can be realized using long-range dipolar interaction in optical lattices, opening the door to quantum simulations of a wide range of lattice models with long-range and anisotropic interactions.
• B. Blakie, L. Chomaz, D. Baillie, F. Ferlaino Compressibility and speeds of sound across the superfluid-to-supersolid phase transition of an elongated dipolar gas, Phys. Rev. Research (2023-09-06), http://dx.doi.org/10.1103/PhysRevResearch.5.033161 doi:10.1103/PhysRevResearch.5.033161
  We investigate the excitation spectrum and compressibility of a dipolar Bose-Einstein condensate in an infinite tube potential in the parameter regime where the transition between superfluid and supersolid phases occurs. Our study focuses on the density range in which crystalline order develops continuously across the transition. Above the transition the superfluid shows a single gapless excitation band, phononic at small momenta and with a roton at a finite momentum. Below the transition, two gapless excitations branches (three at the transition point) emerge in the supersolid. We examine the two gapless excitation bands and their associated speeds of sound in the supersolid phase. Our results show that the speeds of sound and the compressibility are discontinuous at the transition, indicating a second-order phase transition. These results provide valuable insights into the identification of supersolid phenomena in dipolar quantum gases and the relationship to supersolidity in spin-orbit coupled gases.
• T. Bland, G. Lamporesi, M. J. Mark, F. Ferlaino Vortices in dipolar Bose–Einstein condensates, Comptes Rendus Physique 24 20 (2023-09-05), http://dx.doi.org/10.5802/crphys.160 doi:10.5802/crphys.160
  Quantized vortices are the hallmark of superfluidity, and are often sought out as the first observable feature in new superfluid systems. Following the recent experimental observation of vortices in Bose–Einstein condensates comprised of atoms with inherent long-range dipole-dipole interactions [Nat. Phys. 18, 1453-1458 (2022)], we thoroughly investigate vortex properties in the three-dimensional dominantly dipolar regime, where beyond-mean-field effects are crucial for stability, and investigate the interplay between trap geometry and magnetic field tilt angle.
• J. Sánchez-Baena, C. Politi, F. Maucher, F. Ferlaino, T. Pohl Heating a quantum dipolar fluid into a solid, Nat. Commun. 14 1868 (2023-04-04), http://dx.doi.org/10.1038/s41467-023-37207-3 doi:10.1038/s41467-023-37207-3
  Raising the temperature of a material enhances the thermal motion of particles. Such an increase in thermal energy commonly leads to the melting of a solid into a fluid and eventually vaporises the liquid into a gaseous phase of matter. Here, we study the finite-temperature physics of dipolar quantum fluids and find surprising deviations from this general phenomenology. In particular, we describe how heating a dipolar superfluid from near-zero temperatures can induce a phase transition to a supersolid state with a broken translational symmetry. The predicted effect agrees with experimental measurements on ultracold dysprosium atoms, which opens the door for exploring the unusual thermodynamics of dipolar quantum fluids.