@article{15053, abstract = {Atom-based quantum simulators have had many successes in tackling challenging quantum many-body problems, owing to the precise and dynamical control that they provide over the systems' parameters. They are, however, often optimized to address a specific type of problem. Here, we present the design and implementation of a 6Li-based quantum gas platform that provides wide-ranging capabilities and is able to address a variety of quantum many-body problems. Our two-chamber architecture relies on a robust combination of gray molasses and optical transport from a laser-cooling chamber to a glass cell with excellent optical access. There, we first create unitary Fermi superfluids in a three-dimensional axially symmetric harmonic trap and characterize them using in situ thermometry, reaching temperatures below 20 nK. This allows us to enter the deep superfluid regime with samples of extreme diluteness, where the interparticle spacing is sufficiently large for direct single-atom imaging. Second, we generate optical lattice potentials with triangular and honeycomb geometry in which we study diffraction of molecular Bose-Einstein condensates, and show how going beyond the Kapitza-Dirac regime allows us to unambiguously distinguish between the two geometries. With the ability to probe quantum many-body physics in both discrete and continuous space, and its suitability for bulk and single-atom imaging, our setup represents an important step towards achieving a wide-scope quantum simulator.}, author = {Jin, Shuwei and Dai, Kunlun and Verstraten, Joris and Dixmerias, Maxime and Al Hyder, Ragheed and Salomon, Christophe and Peaudecerf, Bruno and de Jongh, Tim and Yefsah, Tarik}, issn = {2643-1564}, journal = {Physical Review Research}, keywords = {General Physics and Astronomy}, number = {1}, publisher = {American Physical Society}, title = {{Multipurpose platform for analog quantum simulation}}, doi = {10.1103/physrevresearch.6.013158}, volume = {6}, year = {2024}, } @article{14486, abstract = {We present a minimal model of ferroelectric large polarons, which are suggested as one of the mechanisms responsible for the unique charge transport properties of hybrid perovskites. We demonstrate that short-ranged charge–rotor interactions lead to long-range ferroelectric ordering of rotors, which strongly affects the carrier mobility. In the nonperturbative regime, where our theory cannot be reduced to any of the earlier models, we reveal that the polaron is characterized by large coherence length and a roughly tenfold increase of the effective mass as compared to the bare mass. These results are in good agreement with other theoretical predictions for ferroelectric polarons. Our model establishes a general phenomenological framework for ferroelectric polarons providing the starting point for future studies of their role in the transport properties of hybrid organic-inorganic perovskites.}, author = {Koutentakis, Georgios and Ghazaryan, Areg and Lemeshko, Mikhail}, issn = {2643-1564}, journal = {Physical Review Research}, number = {4}, publisher = {American Physical Society}, title = {{Rotor lattice model of ferroelectric large polarons}}, doi = {10.1103/PhysRevResearch.5.043016}, volume = {5}, year = {2023}, } @article{14658, abstract = {We investigate spin-charge separation of a spin- 1 2 Fermi system confined in a triple well where multiple bands are occupied. We assume that our finite fermionic system is close to fully spin polarized while being doped by a hole and an impurity fermion with opposite spin. Our setup involves ferromagnetic couplings among the particles in different bands, leading to the development of strong spin-transport correlations in an intermediate interaction regime. Interactions are then strong enough to lift the degeneracy among singlet and triplet spin configurations in the well of the spin impurity but not strong enough to prohibit hole-induced magnetic excitations to the singlet state. Despite the strong spin-hole correlations, the system exhibits spin-charge deconfinement allowing for long-range entanglement of the spatial and spin degrees of freedom.}, author = {Becker, J. M. and Koutentakis, Georgios and Schmelcher, P.}, issn = {2643-1564}, journal = {Physical Review Research}, number = {4}, publisher = {American Physical Society}, title = {{Spin-charge correlations in finite one-dimensional multiband Fermi systems}}, doi = {10.1103/PhysRevResearch.5.043039}, volume = {5}, year = {2023}, } @article{12534, abstract = {Brownian motion of a mobile impurity in a bath is affected by spin-orbit coupling (SOC). Here, we discuss a Caldeira-Leggett-type model that can be used to propose and interpret quantum simulators of this problem in cold Bose gases. First, we derive a master equation that describes the model and explore it in a one-dimensional (1D) setting. To validate the standard assumptions needed for our derivation, we analyze available experimental data without SOC; as a byproduct, this analysis suggests that the quench dynamics of the impurity is beyond the 1D Bose-polaron approach at temperatures currently accessible in a cold-atom laboratory—motion of the impurity is mainly driven by dissipation. For systems with SOC, we demonstrate that 1D spin-orbit coupling can be gauged out even in the presence of dissipation—the information about SOC is incorporated in the initial conditions. Observables sensitive to this information (such as spin densities) can be used to study formation of steady spin polarization domains during quench dynamics.}, author = {Ghazaryan, Areg and Cappellaro, Alberto and Lemeshko, Mikhail and Volosniev, Artem}, issn = {2643-1564}, journal = {Physical Review Research}, number = {1}, publisher = {American Physical Society}, title = {{Dissipative dynamics of an impurity with spin-orbit coupling}}, doi = {10.1103/physrevresearch.5.013029}, volume = {5}, year = {2023}, } @article{10845, abstract = {We study an impurity with a resonance level whose position coincides with the Fermi energy of the surrounding Fermi gas. An impurity causes a rapid variation of the scattering phase shift for fermions at the Fermi surface, introducing a new characteristic length scale into the problem. We investigate manifestations of this length scale in the self-energy of the impurity and in the density of the bath. Our calculations reveal a model-independent deformation of the density of the Fermi gas, which is determined by the width of the resonance. To provide a broader picture, we investigate time evolution of the density in quench dynamics, and study the behavior of the system at finite temperatures. Finally, we briefly discuss implications of our findings for the Fermi-polaron problem.}, author = {Maslov, Mikhail and Lemeshko, Mikhail and Volosniev, Artem}, issn = {2643-1564}, journal = {Physical Review Research}, publisher = {American Physical Society}, title = {{Impurity with a resonance in the vicinity of the Fermi energy}}, doi = {10.1103/PhysRevResearch.4.013160}, volume = {4}, year = {2022}, } @article{11638, abstract = {Statistical inference is central to many scientific endeavors, yet how it works remains unresolved. Answering this requires a quantitative understanding of the intrinsic interplay between statistical models, inference methods, and the structure in the data. To this end, we characterize the efficacy of direct coupling analysis (DCA)—a highly successful method for analyzing amino acid sequence data—in inferring pairwise interactions from samples of ferromagnetic Ising models on random graphs. Our approach allows for physically motivated exploration of qualitatively distinct data regimes separated by phase transitions. We show that inference quality depends strongly on the nature of data-generating distributions: optimal accuracy occurs at an intermediate temperature where the detrimental effects from macroscopic order and thermal noise are minimal. Importantly our results indicate that DCA does not always outperform its local-statistics-based predecessors; while DCA excels at low temperatures, it becomes inferior to simple correlation thresholding at virtually all temperatures when data are limited. Our findings offer insights into the regime in which DCA operates so successfully, and more broadly, how inference interacts with the structure in the data.}, author = {Ngampruetikorn, Vudtiwat and Sachdeva, Vedant and Torrence, Johanna and Humplik, Jan and Schwab, David J. and Palmer, Stephanie E.}, issn = {2643-1564}, journal = {Physical Review Research}, number = {2}, publisher = {American Physical Society}, title = {{Inferring couplings in networks across order-disorder phase transitions}}, doi = {10.1103/PhysRevResearch.4.023240}, volume = {4}, year = {2022}, } @article{10652, abstract = {Finding a feasible scheme for testing the quantum mechanical nature of the gravitational interaction has been attracting an increasing level of attention. Gravity mediated entanglement generation so far appears to be the key ingredient for a potential experiment. In a recent proposal [D. Carney et al., PRX Quantum 2, 030330 (2021)] combining an atom interferometer with a low-frequency mechanical oscillator, a coherence revival test is proposed for verifying this entanglement generation. With measurements performed only on the atoms, this protocol bypasses the need for correlation measurements. Here, we explore formulations of such a protocol, and specifically find that in the envisioned regime of operation with high thermal excitation, semiclassical models, where there is no concept of entanglement, also give the same experimental signatures. We elucidate in a fully quantum mechanical calculation that entanglement is not the source of the revivals in the relevant parameter regime. We argue that, in its current form, the suggested test is only relevant if the oscillator is nearly in a pure quantum state, and in this regime the effects are too small to be measurable. We further discuss potential open ends. The results highlight the importance and subtleties of explicitly considering how the quantum case differs from the classical expectations when testing for the quantum mechanical nature of a physical system.}, author = {Hosten, Onur}, issn = {2643-1564}, journal = {Physical Review Research}, number = {1}, publisher = {American Physical Society}, title = {{Constraints on probing quantum coherence to infer gravitational entanglement}}, doi = {10.1103/PhysRevResearch.4.013023}, volume = {4}, year = {2022}, } @article{12111, abstract = {Quantum impurities exhibit fascinating many-body phenomena when the small interacting impurity changes the physics of a large noninteracting environment. The characterisation of such strongly correlated nonperturbative effects is particularly challenging due to the infinite size of the environment, and the inability of local correlators to capture the buildup of long-ranged entanglement in the system. Here, we harness an entanglement-based observable—the purity of the impurity—as a witness for the formation of strong correlations. We showcase the utility of our scheme by exactly solving the open Kondo box model in the small box limit, and thus describe all-electronic dot-cavity devices. Specifically, we conclusively characterize the metal-to-insulator phase transition in the system and identify how the (conducting) dot-lead Kondo singlet is quenched by an (insulating) intraimpurity singlet formation. Furthermore, we propose an experimentally feasible tomography protocol for the measurement of the purity, which motivates the observation of impurity physics through their entanglement build up.}, author = {Stocker, Lidia and Sack, Stefan and Ferguson, Michael S. and Zilberberg, Oded}, issn = {2643-1564}, journal = {Physical Review Research}, number = {4}, publisher = {American Physical Society}, title = {{Entanglement-based observables for quantum impurities}}, doi = {10.1103/PhysRevResearch.4.043177}, volume = {4}, year = {2022}, } @article{10559, abstract = {Hole gases in planar germanium can have high mobilities in combination with strong spin-orbit interaction and electrically tunable g factors, and are therefore emerging as a promising platform for creating hybrid superconductor-semiconductor devices. A key challenge towards hybrid Ge-based quantum technologies is the design of high-quality interfaces and superconducting contacts that are robust against magnetic fields. In this work, by combining the assets of aluminum, which provides good contact to the Ge, and niobium, which has a significant superconducting gap, we demonstrate highly transparent low-disordered JoFETs with relatively large ICRN products that are capable of withstanding high magnetic fields. We furthermore demonstrate the ability of phase-biasing individual JoFETs, opening up an avenue to explore topological superconductivity in planar Ge. The persistence of superconductivity in the reported hybrid devices beyond 1.8 T paves the way towards integrating spin qubits and proximity-induced superconductivity on the same chip.}, author = {Aggarwal, Kushagra and Hofmann, Andrea C and Jirovec, Daniel and Prieto Gonzalez, Ivan and Sammak, Amir and Botifoll, Marc and Martí-Sánchez, Sara and Veldhorst, Menno and Arbiol, Jordi and Scappucci, Giordano and Danon, Jeroen and Katsaros, Georgios}, issn = {2643-1564}, journal = {Physical Review Research}, keywords = {general engineering}, number = {2}, publisher = {American Physical Society}, title = {{Enhancement of proximity-induced superconductivity in a planar Ge hole gas}}, doi = {10.1103/physrevresearch.3.l022005}, volume = {3}, year = {2021}, } @article{12071, abstract = {Despite many efforts to rationalize the strongly correlated electronic ground states in doped Mott insulators, the nature of the doping-induced insulator-to-metal transition is still a subject under intensive investigation. Here, we probe the nanoscale electronic structure of the Mott insulator Sr₂IrO₄δ with low-temperature scanning tunneling microscopy and find an enhanced local density of states (LDOS) inside the Mott gap at the location of individual defects which we interpret as defects at apical oxygen sites. A chiral behavior in the topography for those defects has been observed. We also visualize the local enhanced conductance arising from the overlapping of defect states which induces finite LDOS inside of the Mott gap. By combining these findings with the typical spatial extension of isolated defects of about 2 nm, our results indicate that the insulator-to-metal transition in Sr₂IrO₄−δ could be percolative in nature.}, author = {Sun, Zhixiang and Guevara, Jose M. and Sykora, Steffen and Paerschke, Ekaterina and Manna, Kaustuv and Maljuk, Andrey and Wurmehl, Sabine and van den Brink, Jeroen and Büchner, Bernd and Hess, Christian}, issn = {2643-1564}, journal = {Physical Review Research}, number = {2}, publisher = {American Physical Society}, title = {{Evidence for a percolative Mott insulator-metal transition in doped Sr₂IrO₄}}, doi = {10.1103/physrevresearch.3.023075}, volume = {3}, year = {2021}, } @article{7919, abstract = {We explore the time evolution of two impurities in a trapped one-dimensional Bose gas that follows a change of the boson-impurity interaction. We study the induced impurity-impurity interactions and their effect on the quench dynamics. In particular, we report on the size of the impurity cloud, the impurity-impurity entanglement, and the impurity-impurity correlation function. The presented numerical simulations are based upon the variational multilayer multiconfiguration time-dependent Hartree method for bosons. To analyze and quantify induced impurity-impurity correlations, we employ an effective two-body Hamiltonian with a contact interaction. We show that the effective model consistent with the mean-field attraction of two heavy impurities explains qualitatively our results for weak interactions. Our findings suggest that the quench dynamics in cold-atom systems can be a tool for studying impurity-impurity correlations.}, author = {Mistakidis, S. I. and Volosniev, Artem and Schmelcher, P.}, issn = {2643-1564}, journal = {Physical Review Research}, publisher = {American Physical Society}, title = {{Induced correlations between impurities in a one-dimensional quenched Bose gas}}, doi = {10.1103/physrevresearch.2.023154}, volume = {2}, year = {2020}, } @article{8011, abstract = {Relaxation to a thermal state is the inevitable fate of nonequilibrium interacting quantum systems without special conservation laws. While thermalization in one-dimensional systems can often be suppressed by integrability mechanisms, in two spatial dimensions thermalization is expected to be far more effective due to the increased phase space. In this work we propose a general framework for escaping or delaying the emergence of the thermal state in two-dimensional arrays of Rydberg atoms via the mechanism of quantum scars, i.e., initial states that fail to thermalize. The suppression of thermalization is achieved in two complementary ways: by adding local perturbations or by adjusting the driving Rabi frequency according to the local connectivity of the lattice. We demonstrate that these mechanisms allow us to realize robust quantum scars in various two-dimensional lattices, including decorated lattices with nonconstant connectivity. In particular, we show that a small decrease of the Rabi frequency at the corners of the lattice is crucial for mitigating the strong boundary effects in two-dimensional systems. Our results identify synchronization as an important tool for future experiments on two-dimensional quantum scars.}, author = {Michailidis, Alexios and Turner, C. J. and Papić, Z. and Abanin, D. A. and Serbyn, Maksym}, issn = {2643-1564}, journal = {Physical Review Research}, number = {2}, publisher = {American Physical Society}, title = {{Stabilizing two-dimensional quantum scars by deformation and synchronization}}, doi = {10.1103/physrevresearch.2.022065}, volume = {2}, year = {2020}, } @article{7190, abstract = {We investigate the ground-state energy of a one-dimensional Fermi gas with two bosonic impurities. We consider spinless fermions with no fermion-fermion interactions. The fermion-impurity and impurity-impurity interactions are modeled with Dirac delta functions. First, we study the case where impurity and fermion have equal masses, and the impurity-impurity two-body interaction is identical to the fermion-impurity interaction, such that the system is solvable with the Bethe ansatz. For attractive interactions, we find that the energy of the impurity-impurity subsystem is below the energy of the bound state that exists without the Fermi gas. We interpret this as a manifestation of attractive boson-boson interactions induced by the fermionic medium, and refer to the impurity-impurity subsystem as an in-medium bound state. For repulsive interactions, we find no in-medium bound states. Second, we construct an effective model to describe these interactions, and compare its predictions to the exact solution. We use this effective model to study nonintegrable systems with unequal masses and/or potentials. We discuss parameter regimes for which impurity-impurity attraction induced by the Fermi gas can lead to the formation of in-medium bound states made of bosons that repel each other in the absence of the Fermi gas.}, author = {Huber, D. and Hammer, H.-W. and Volosniev, Artem}, issn = {2643-1564}, journal = {Physical Review Research}, number = {3}, publisher = {American Physical Society}, title = {{In-medium bound states of two bosonic impurities in a one-dimensional Fermi gas}}, doi = {10.1103/physrevresearch.1.033177}, volume = {1}, year = {2019}, }