@article{14845, abstract = {We study a linear rotor in a bosonic bath within the angulon formalism. Our focus is on systems where isotropic or anisotropic impurity-boson interactions support a shallow bound state. To study the fate of the angulon in the vicinity of bound-state formation, we formulate a beyond-linear-coupling angulon Hamiltonian. First, we use it to study attractive, spherically symmetric impurity-boson interactions for which the linear rotor can be mapped onto a static impurity. The well-known polaron formalism provides an adequate description in this limit. Second, we consider anisotropic potentials, and show that the presence of a shallow bound state with pronounced anisotropic character leads to a many-body instability that washes out the angulon dynamics.}, author = {Dome, Tibor and Volosniev, Artem and Ghazaryan, Areg and Safari, Laleh and Schmidt, Richard and Lemeshko, Mikhail}, issn = {2469-9969}, journal = {Physical Review B}, number = {1}, publisher = {American Physical Society}, title = {{Linear rotor in an ideal Bose gas near the threshold for binding}}, doi = {10.1103/PhysRevB.109.014102}, volume = {109}, year = {2024}, } @article{15045, abstract = {Coupling of orbital motion to a spin degree of freedom gives rise to various transport phenomena in quantum systems that are beyond the standard paradigms of classical physics. Here, we discuss features of spin-orbit dynamics that can be visualized using a classical model with two coupled angular degrees of freedom. Specifically, we demonstrate classical ‘spin’ filtering through our model and show that the interplay between angular degrees of freedom and dissipation can lead to asymmetric ‘spin’ transport.}, author = {Varshney, Atul and Ghazaryan, Areg and Volosniev, Artem}, issn = {1432-5411}, journal = {Few-Body Systems}, keywords = {Atomic and Molecular Physics, and Optics}, publisher = {Springer Nature}, title = {{Classical ‘spin’ filtering with two degrees of freedom and dissipation}}, doi = {10.1007/s00601-024-01880-x}, volume = {65}, year = {2024}, } @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{13251, abstract = {A rotating organic cation and a dynamically disordered soft inorganic cage are the hallmark features of organic-inorganic lead-halide perovskites. Understanding the interplay between these two subsystems is a challenging problem, but it is this coupling that is widely conjectured to be responsible for the unique behavior of photocarriers in these materials. In this work, we use the fact that the polarizability of the organic cation strongly depends on the ambient electrostatic environment to put the molecule forward as a sensitive probe of the local crystal fields inside the lattice cell. We measure the average polarizability of the C/N–H bond stretching mode by means of infrared spectroscopy, which allows us to deduce the character of the motion of the cation molecule, find the magnitude of the local crystal field, and place an estimate on the strength of the hydrogen bond between the hydrogen and halide atoms. Our results pave the way for understanding electric fields in lead-halide perovskites using infrared bond spectroscopy.}, author = {Wei, Yujing and Volosniev, Artem and Lorenc, Dusan and Zhumekenov, Ayan A. and Bakr, Osman M. and Lemeshko, Mikhail and Alpichshev, Zhanybek}, issn = {1948-7185}, journal = {The Journal of Physical Chemistry Letters}, keywords = {General Materials Science, Physical and Theoretical Chemistry}, number = {27}, pages = {6309--6314}, publisher = {American Chemical Society}, title = {{Bond polarizability as a probe of local crystal fields in hybrid lead-halide perovskites}}, doi = {10.1021/acs.jpclett.3c01158}, volume = {14}, year = {2023}, } @article{13276, abstract = {We introduce a generic and accessible implementation of an exact diagonalization method for studying few-fermion models. Our aim is to provide a testbed for the newcomers to the field as well as a stepping stone for trying out novel optimizations and approximations. This userguide consists of a description of the algorithm, and several examples in varying orders of sophistication. In particular, we exemplify our routine using an effective-interaction approach that fixes the low-energy physics. We benchmark this approach against the existing data, and show that it is able to deliver state-of-the-art numerical results at a significantly reduced computational cost.}, author = {Rammelmüller, Lukas and Huber, David and Volosniev, Artem}, issn = {2949-804X}, journal = {SciPost Physics Codebases}, publisher = {SciPost Foundation}, title = {{A modular implementation of an effective interaction approach for harmonically trapped fermions in 1D}}, doi = {10.21468/scipostphyscodeb.12}, year = {2023}, } @misc{13275, abstract = {We introduce a generic and accessible implementation of an exact diagonalization method for studying few-fermion models. Our aim is to provide a testbed for the newcomers to the field as well as a stepping stone for trying out novel optimizations and approximations. This userguide consists of a description of the algorithm, and several examples in varying orders of sophistication. In particular, we exemplify our routine using an effective-interaction approach that fixes the low-energy physics. We benchmark this approach against the existing data, and show that it is able to deliver state-of-the-art numerical results at a significantly reduced computational cost.}, author = {Rammelmüller, Lukas and Huber, David and Volosniev, Artem}, publisher = {SciPost Foundation}, title = {{Codebase release 1.0 for FermiFCI}}, doi = {10.21468/scipostphyscodeb.12-r1.0}, year = {2023}, } @article{12723, abstract = {Lead halide perovskites enjoy a number of remarkable optoelectronic properties. To explain their origin, it is necessary to study how electromagnetic fields interact with these systems. We address this problem here by studying two classical quantities: Faraday rotation and the complex refractive index in a paradigmatic perovskite CH3NH3PbBr3 in a broad wavelength range. We find that the minimal coupling of electromagnetic fields to the k⋅p Hamiltonian is insufficient to describe the observed data even on the qualitative level. To amend this, we demonstrate that there exists a relevant atomic-level coupling between electromagnetic fields and the spin degree of freedom. This spin-electric coupling allows for quantitative description of a number of previous as well as present experimental data. In particular, we use it here to show that the Faraday effect in lead halide perovskites is dominated by the Zeeman splitting of the energy levels and has a substantial beyond-Becquerel contribution. Finally, we present general symmetry-based phenomenological arguments that in the low-energy limit our effective model includes all basis coupling terms to the electromagnetic field in the linear order.}, author = {Volosniev, Artem and Shiva Kumar, Abhishek and Lorenc, Dusan and Ashourishokri, Younes and Zhumekenov, Ayan A. and Bakr, Osman M. and Lemeshko, Mikhail and Alpichshev, Zhanybek}, issn = {1079-7114}, journal = {Physical Review Letters}, keywords = {General Physics and Astronomy}, number = {10}, publisher = {American Physical Society}, title = {{Spin-electric coupling in lead halide perovskites}}, doi = {10.1103/physrevlett.130.106901}, volume = {130}, year = {2023}, } @article{12724, abstract = {We use general symmetry-based arguments to construct an effective model suitable for studying optical properties of lead halide perovskites. To build the model, we identify an atomic-level interaction between electromagnetic fields and the spin degree of freedom that should be added to a minimally coupled k⋅p Hamiltonian. As a first application, we study two basic optical characteristics of the material: the Verdet constant and the refractive index. Beyond these linear characteristics of the material, the model is suitable for calculating nonlinear effects such as the third-order optical susceptibility. Analysis of this quantity shows that the geometrical properties of the spin-electric term imply isotropic optical response of the system, and that optical anisotropy of lead halide perovskites is a manifestation of hopping of charge carriers. To illustrate this, we discuss third-harmonic generation.}, author = {Volosniev, Artem and Shiva Kumar, Abhishek and Lorenc, Dusan and Ashourishokri, Younes and Zhumekenov, Ayan and Bakr, Osman M. and Lemeshko, Mikhail and Alpichshev, Zhanybek}, issn = {2469-9969}, journal = {Physical Review B}, number = {12}, publisher = {American Physical Society}, title = {{Effective model for studying optical properties of lead halide perovskites}}, doi = {10.1103/physrevb.107.125201}, volume = {107}, year = {2023}, } @article{13233, abstract = {We study the impact of finite-range physics on the zero-range-model analysis of three-body recombination in ultracold atoms. We find that temperature dependence of the zero-range parameters can vary from one set of measurements to another as it may be driven by the distribution of error bars in the experiment, and not by the underlying three-body physics. To study finite-temperature effects in three-body recombination beyond the zero-range physics, we introduce and examine a finite-range model based upon a hyperspherical formalism. The systematic error discussed in this Letter may provide a significant contribution to the error bars of measured three-body parameters.}, author = {Agafonova, Sofya and Lemeshko, Mikhail and Volosniev, Artem}, issn = {2469-9934}, journal = {Physical Review A}, number = {6}, publisher = {American Physical Society}, title = {{Finite-range bias in fitting three-body loss to the zero-range model}}, doi = {10.1103/PhysRevA.107.L061304}, volume = {107}, year = {2023}, } @article{14321, abstract = {We demonstrate the possibility of a coupling between the magnetization direction of a ferromagnet and the tilting angle of adsorbed achiral molecules. To illustrate the mechanism of the coupling, we analyze a minimal Stoner model that includes Rashba spin–orbit coupling due to the electric field on the surface of the ferromagnet. The proposed mechanism allows us to study magnetic anisotropy of the system with an extended Stoner–Wohlfarth model and argue that adsorbed achiral molecules can change magnetocrystalline anisotropy of the substrate. Our research aims to motivate further experimental studies of the current-free chirality induced spin selectivity effect involving both enantiomers.}, author = {Al Hyder, Ragheed and Cappellaro, Alberto and Lemeshko, Mikhail and Volosniev, Artem}, issn = {1089-7690}, journal = {The Journal of Chemical Physics}, keywords = {Physical and Theoretical Chemistry, General Physics and Astronomy}, number = {10}, publisher = {AIP Publishing}, title = {{Achiral dipoles on a ferromagnet can affect its magnetization direction}}, doi = {10.1063/5.0165806}, volume = {159}, year = {2023}, } @article{14037, abstract = {Traditionally, nuclear spin is not considered to affect biological processes. Recently, this has changed as isotopic fractionation that deviates from classical mass dependence was reported both in vitro and in vivo. In these cases, the isotopic effect correlates with the nuclear magnetic spin. Here, we show nuclear spin effects using stable oxygen isotopes (16O, 17O, and 18O) in two separate setups: an artificial dioxygen production system and biological aquaporin channels in cells. We observe that oxygen dynamics in chiral environments (in particular its transport) depend on nuclear spin, suggesting future applications for controlled isotope separation to be used, for instance, in NMR. To demonstrate the mechanism behind our findings, we formulate theoretical models based on a nuclear-spin-enhanced switch between electronic spin states. Accounting for the role of nuclear spin in biology can provide insights into the role of quantum effects in living systems and help inspire the development of future biotechnology solutions.}, author = {Vardi, Ofek and Maroudas-Sklare, Naama and Kolodny, Yuval and Volosniev, Artem and Saragovi, Amijai and Galili, Nir and Ferrera, Stav and Ghazaryan, Areg and Yuran, Nir and Affek, Hagit P. and Luz, Boaz and Goldsmith, Yonaton and Keren, Nir and Yochelis, Shira and Halevy, Itay and Lemeshko, Mikhail and Paltiel, Yossi}, issn = {1091-6490}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, number = {32}, publisher = {National Academy of Sciences}, title = {{Nuclear spin effects in biological processes}}, doi = {10.1073/pnas.2300828120}, volume = {120}, year = {2023}, } @article{14513, abstract = {Cold atomic gases have become a paradigmatic system for exploring fundamental physics, which at the same time allows for applications in quantum technologies. The accelerating developments in the field have led to a highly advanced set of engineering techniques that, for example, can tune interactions, shape the external geometry, select among a large set of atomic species with different properties, or control the number of atoms. In particular, it is possible to operate in lower dimensions and drive atomic systems into the strongly correlated regime. In this review, we discuss recent advances in few-body cold atom systems confined in low dimensions from a theoretical viewpoint. We mainly focus on bosonic systems in one dimension and provide an introduction to the static properties before we review the state-of-the-art research into quantum dynamical processes stimulated by the presence of correlations. Besides discussing the fundamental physical phenomena arising in these systems, we also provide an overview of the calculational and numerical tools and methods that are commonly used, thus delivering a balanced and comprehensive overview of the field. We conclude by giving an outlook on possible future directions that are interesting to explore in these correlated systems.}, author = {Mistakidis, S. I. and Volosniev, Artem and Barfknecht, R. E. and Fogarty, T. and Busch, Th and Foerster, A. and Schmelcher, P. and Zinner, N. T.}, issn = {0370-1573}, journal = {Physics Reports}, pages = {1--108}, publisher = {Elsevier}, title = {{Few-body Bose gases in low dimensions - A laboratory for quantum dynamics}}, doi = {10.1016/j.physrep.2023.10.004}, volume = {1042}, year = {2023}, } @article{14650, abstract = {We study the out-of-equilibrium quantum dynamics of dipolar polarons, i.e., impurities immersed in a dipolar Bose-Einstein condensate, after a quench of the impurity-boson interaction. We show that the dipolar nature of the condensate and of the impurity results in anisotropic relaxation dynamics, in particular, anisotropic dressing of the polaron. More relevantly for cold-atom setups, quench dynamics is strongly affected by the interplay between dipolar anisotropy and trap geometry. Our findings pave the way for simulating impurities in anisotropic media utilizing experiments with dipolar mixtures.}, author = {Volosniev, Artem and Bighin, Giacomo and Santos, Luis and Peña Ardila, Luisllu A.}, issn = {2542-4653}, journal = {SciPost Physics}, keywords = {General Physics and Astronomy}, number = {6}, publisher = {SciPost Foundation}, title = {{Non-equilibrium dynamics of dipolar polarons}}, doi = {10.21468/scipostphys.15.6.232}, volume = {15}, year = {2023}, } @article{13278, abstract = {We present a numerical analysis of spin-1/2 fermions in a one-dimensional harmonic potential in the presence of a magnetic point-like impurity at the center of the trap. The model represents a few-body analogue of a magnetic impurity in the vicinity of an s-wave superconductor. Already for a few particles we find a ground-state level crossing between sectors with different fermion parities. We interpret this crossing as a few-body precursor of a quantum phase transition, which occurs when the impurity "breaks" a Cooper pair. This picture is further corroborated by analyzing density-density correlations in momentum space. Finally, we discuss how the system may be realized with existing cold-atoms platforms.}, author = {Rammelmüller, Lukas and Huber, David and Čufar, Matija and Brand, Joachim and Hammer, Hans-Werner and Volosniev, Artem}, issn = {2542-4653}, journal = {SciPost Physics}, keywords = {General Physics and Astronomy}, number = {1}, publisher = {SciPost Foundation}, title = {{Magnetic impurity in a one-dimensional few-fermion system}}, doi = {10.21468/scipostphys.14.1.006}, volume = {14}, year = {2023}, } @article{14246, abstract = {The model of a ring threaded by the Aharonov-Bohm flux underlies our understanding of a coupling between gauge potentials and matter. The typical formulation of the model is based upon a single particle picture, and should be extended when interactions with other particles become relevant. Here, we illustrate such an extension for a particle in an Aharonov-Bohm ring subject to interactions with a weakly interacting Bose gas. We show that the ground state of the system can be described using the Bose-polaron concept—a particle dressed by interactions with a bosonic environment. We connect the energy spectrum to the effective mass of the polaron, and demonstrate how to change currents in the system by tuning boson-particle interactions. Our results suggest the Aharonov-Bohm ring as a platform for studying coherence and few- to many-body crossover of quasi-particles that arise from an impurity immersed in a medium.}, author = {Brauneis, Fabian and Ghazaryan, Areg and Hammer, Hans-Werner and Volosniev, Artem}, issn = {2399-3650}, journal = {Communications Physics}, keywords = {General Physics and Astronomy}, publisher = {Springer Nature}, title = {{Emergence of a Bose polaron in a small ring threaded by the Aharonov-Bohm flux}}, doi = {10.1038/s42005-023-01281-2}, volume = {6}, 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{11590, abstract = {We investigate the ground-state properties of weakly repulsive one-dimensional bosons in the presence of an attractive zero-range impurity potential. First, we derive mean-field solutions to the problem on a finite ring for the two asymptotic cases: (i) all bosons are bound to the impurity and (ii) all bosons are in a scattering state. Moreover, we derive the critical line that separates these regimes in the parameter space. In the thermodynamic limit, this critical line determines the maximum number of bosons that can be bound by the impurity potential, forming an artificial atom. Second, we validate the mean-field results using the flow equation approach and the multi-layer multi-configuration time-dependent Hartree method for atomic mixtures. While beyond-mean-field effects destroy long-range order in the Bose gas, the critical boson number is unaffected. Our findings are important for understanding such artificial atoms in low-density Bose gases with static and mobile impurities.}, author = {Brauneis, Fabian and Backert, Timothy G. and Mistakidis, Simeon I. and Lemeshko, Mikhail and Hammer, Hans Werner and Volosniev, Artem}, issn = {1367-2630}, journal = {New Journal of Physics}, number = {6}, publisher = {IOP Publishing}, title = {{Artificial atoms from cold bosons in one dimension}}, doi = {10.1088/1367-2630/ac78d8}, volume = {24}, year = {2022}, } @article{9093, abstract = {We employ the Gross-Pitaevskii equation to study acoustic emission generated in a uniform Bose gas by a static impurity. The impurity excites a sound-wave packet, which propagates through the gas. We calculate the shape of this wave packet in the limit of long wave lengths, and argue that it is possible to extract properties of the impurity by observing this shape. We illustrate here this possibility for a Bose gas with a trapped impurity atom -- an example of a relevant experimental setup. Presented results are general for all one-dimensional systems described by the nonlinear Schrödinger equation and can also be used in nonatomic systems, e.g., to analyze light propagation in nonlinear optical media. Finally, we calculate the shape of the sound-wave packet for a three-dimensional Bose gas assuming a spherically symmetric perturbation.}, author = {Marchukov, Oleksandr and Volosniev, Artem}, issn = {2542-4653}, journal = {SciPost Physics}, number = {2}, publisher = {SciPost Foundation}, title = {{Shape of a sound wave in a weakly-perturbed Bose gas}}, doi = {10.21468/scipostphys.10.2.025}, volume = {10}, year = {2021}, } @article{9679, abstract = {The relative motion of three impenetrable particles on a ring, in our case two identical fermions and one impurity, is isomorphic to a triangular quantum billiard. Depending on the ratio κ of the impurity and fermion masses, the billiards can be integrable or non-integrable (also referred to in the main text as chaotic). To set the stage, we first investigate the energy level distributions of the billiards as a function of 1/κ ∈ [0, 1] and find no evidence of integrable cases beyond the limiting values 1/κ = 1 and 1/κ = 0. Then, we use machine learning tools to analyze properties of probability distributions of individual quantum states. We find that convolutional neural networks can correctly classify integrable and non-integrable states. The decisive features of the wave functions are the normalization and a large number of zero elements, corresponding to the existence of a nodal line. The network achieves typical accuracies of 97%, suggesting that machine learning tools can be used to analyze and classify the morphology of probability densities obtained in theory or experiment.}, author = {Huber, David and Marchukov, Oleksandr V. and Hammer, Hans Werner and Volosniev, Artem}, issn = {13672630}, journal = {New Journal of Physics}, number = {6}, publisher = {IOP Publishing}, title = {{Morphology of three-body quantum states from machine learning}}, doi = {10.1088/1367-2630/ac0576}, volume = {23}, year = {2021}, } @article{9770, abstract = {We study an effective one-dimensional quantum model that includes friction and spin-orbit coupling (SOC), and show that the model exhibits spin polarization when both terms are finite. Most important, strong spin polarization can be observed even for moderate SOC, provided that the friction is strong. Our findings might help to explain the pronounced effect of chirality on spin distribution and transport in chiral molecules. In particular, our model implies static magnetic properties of a chiral molecule, which lead to Shiba-like states when a molecule is placed on a superconductor, in accordance with recent experimental data.}, author = {Volosniev, Artem and Alpern, Hen and Paltiel, Yossi and Millo, Oded and Lemeshko, Mikhail and Ghazaryan, Areg}, issn = {2469-9969}, journal = {Physical Review B}, number = {2}, publisher = {American Physical Society}, title = {{Interplay between friction and spin-orbit coupling as a source of spin polarization}}, doi = {10.1103/physrevb.104.024430}, volume = {104}, year = {2021}, }