TY - JOUR AB - 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. AU - Al Hyder, Ragheed AU - Cappellaro, Alberto AU - Lemeshko, Mikhail AU - Volosniev, Artem ID - 14321 IS - 10 JF - The Journal of Chemical Physics KW - Physical and Theoretical Chemistry KW - General Physics and Astronomy SN - 0021-9606 TI - Achiral dipoles on a ferromagnet can affect its magnetization direction VL - 159 ER - TY - JOUR AB - Coherent control and manipulation of quantum degrees of freedom such as spins forms the basis of emerging quantum technologies. In this context, the robust valley degree of freedom and the associated valley pseudospin found in two-dimensional transition metal dichalcogenides is a highly attractive platform. Valley polarization and coherent superposition of valley states have been observed in these systems even up to room temperature. Control of valley coherence is an important building block for the implementation of valley qubit. Large magnetic fields or high-power lasers have been used in the past to demonstrate the control (initialization and rotation) of the valley coherent states. Here, the control of layer–valley coherence via strong coupling of valley excitons in bilayer WS2 to microcavity photons is demonstrated by exploiting the pseudomagnetic field arising in optical cavities owing to the transverse electric–transverse magnetic (TE–TM)mode splitting. The use of photonic structures to generate pseudomagnetic fields which can be used to manipulate exciton-polaritons presents an attractive approach to control optical responses without the need for large magnets or high-intensity optical pump powers. AU - Khatoniar, Mandeep AU - Yama, Nicholas AU - Ghazaryan, Areg AU - Guddala, Sriram AU - Ghaemi, Pouyan AU - Majumdar, Kausik AU - Menon, Vinod ID - 12836 IS - 13 JF - Advanced Optical Materials TI - Optical manipulation of Layer–Valley coherence via strong exciton–photon coupling in microcavities VL - 11 ER - TY - JOUR AB - 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. AU - Vardi, Ofek AU - Maroudas-Sklare, Naama AU - Kolodny, Yuval AU - Volosniev, Artem AU - Saragovi, Amijai AU - Galili, Nir AU - Ferrera, Stav AU - Ghazaryan, Areg AU - Yuran, Nir AU - Affek, Hagit P. AU - Luz, Boaz AU - Goldsmith, Yonaton AU - Keren, Nir AU - Yochelis, Shira AU - Halevy, Itay AU - Lemeshko, Mikhail AU - Paltiel, Yossi ID - 14037 IS - 32 JF - Proceedings of the National Academy of Sciences of the United States of America TI - Nuclear spin effects in biological processes VL - 120 ER - TY - JOUR AB - 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. AU - Koutentakis, Georgios AU - Ghazaryan, Areg AU - Lemeshko, Mikhail ID - 14486 IS - 4 JF - Physical Review Research SN - 2643-1564 TI - Rotor lattice model of ferroelectric large polarons VL - 5 ER - TY - JOUR AB - 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. AU - Mistakidis, S. I. AU - Volosniev, Artem AU - Barfknecht, R. E. AU - Fogarty, T. AU - Busch, Th AU - Foerster, A. AU - Schmelcher, P. AU - Zinner, N. T. ID - 14513 JF - Physics Reports SN - 0370-1573 TI - Few-body Bose gases in low dimensions - A laboratory for quantum dynamics VL - 1042 ER - TY - JOUR AB - 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. AU - Becker, J. M. AU - Koutentakis, Georgios AU - Schmelcher, P. ID - 14658 IS - 4 JF - Physical Review Research SN - 2643-1564 TI - Spin-charge correlations in finite one-dimensional multiband Fermi systems VL - 5 ER - TY - JOUR AB - 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. AU - Volosniev, Artem AU - Bighin, Giacomo AU - Santos, Luis AU - Peña Ardila, Luisllu A. ID - 14650 IS - 6 JF - SciPost Physics KW - General Physics and Astronomy SN - 2542-4653 TI - Non-equilibrium dynamics of dipolar polarons VL - 15 ER - TY - JOUR AB - 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. AU - Rammelmüller, Lukas AU - Huber, David AU - Čufar, Matija AU - Brand, Joachim AU - Hammer, Hans-Werner AU - Volosniev, Artem ID - 13278 IS - 1 JF - SciPost Physics KW - General Physics and Astronomy SN - 2542-4653 TI - Magnetic impurity in a one-dimensional few-fermion system VL - 14 ER - TY - JOUR AB - 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. AU - Brauneis, Fabian AU - Ghazaryan, Areg AU - Hammer, Hans-Werner AU - Volosniev, Artem ID - 14246 JF - Communications Physics KW - General Physics and Astronomy SN - 2399-3650 TI - Emergence of a Bose polaron in a small ring threaded by the Aharonov-Bohm flux VL - 6 ER - TY - JOUR AB - We demonstrate that a sodium dimer, Na2(13Σ+u), residing on the surface of a helium nanodroplet, can be set into rotation by a nonresonant 1.0 ps infrared laser pulse. The time-dependent degree of alignment measured, exhibits a periodic, gradually decreasing structure that deviates qualitatively from that expected for gas-phase dimers. Comparison to alignment dynamics calculated from the time-dependent rotational Schrödinger equation shows that the deviation is due to the alignment dependent interaction between the dimer and the droplet surface. This interaction confines the dimer to the tangential plane of the droplet surface at the point where it resides and is the reason that the observed alignment dynamics is also well described by a 2D quantum rotor model. AU - Kranabetter, Lorenz AU - Kristensen, Henrik H. AU - Ghazaryan, Areg AU - Schouder, Constant A. AU - Chatterley, Adam S. AU - Janssen, Paul AU - Jensen, Frank AU - Zillich, Robert E. AU - Lemeshko, Mikhail AU - Stapelfeldt, Henrik ID - 14238 IS - 5 JF - Physical Review Letters SN - 0031-9007 TI - Nonadiabatic laser-induced alignment dynamics of molecules on a surface VL - 131 ER - TY - JOUR AB - We prove the r-spin cobordism hypothesis in the setting of (weak) 2-categories for every positive integer r: the 2-groupoid of 2-dimensional fully extended r-spin TQFTs with given target is equivalent to the homotopy fixed points of an induced Spin 2r -action. In particular, such TQFTs are classified by fully dualisable objects together with a trivialisation of the rth power of their Serre automorphisms. For r=1, we recover the oriented case (on which our proof builds), while ordinary spin structures correspond to r=2. To construct examples, we explicitly describe Spin 2r​-homotopy fixed points in the equivariant completion of any symmetric monoidal 2-category. We also show that every object in a 2-category of Landau–Ginzburg models gives rise to fully extended spin TQFTs and that half of these do not factor through the oriented bordism 2-category. AU - Carqueville, Nils AU - Szegedy, Lorant ID - 14756 IS - 3 JF - Quantum Topology KW - Geometry and Topology KW - Mathematical Physics SN - 1663-487X TI - Fully extended r-spin TQFTs VL - 14 ER - TY - JOUR AB - 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. AU - Maslov, Mikhail AU - Lemeshko, Mikhail AU - Volosniev, Artem ID - 10845 JF - Physical Review Research SN - 2643-1564 TI - Impurity with a resonance in the vicinity of the Fermi energy VL - 4 ER - TY - JOUR AB - A critical overview of the theory of the chirality-induced spin selectivity (CISS) effect, that is, phenomena in which the chirality of molecular species imparts significant spin selectivity to various electron processes, is provided. Based on discussions in a recently held workshop, and further work published since, the status of CISS effects—in electron transmission, electron transport, and chemical reactions—is reviewed. For each, a detailed discussion of the state-of-the-art in theoretical understanding is provided and remaining challenges and research opportunities are identified. AU - Evers, Ferdinand AU - Aharony, Amnon AU - Bar-Gill, Nir AU - Entin-Wohlman, Ora AU - Hedegård, Per AU - Hod, Oded AU - Jelinek, Pavel AU - Kamieniarz, Grzegorz AU - Lemeshko, Mikhail AU - Michaeli, Karen AU - Mujica, Vladimiro AU - Naaman, Ron AU - Paltiel, Yossi AU - Refaely-Abramson, Sivan AU - Tal, Oren AU - Thijssen, Jos AU - Thoss, Michael AU - Van Ruitenbeek, Jan M. AU - Venkataraman, Latha AU - Waldeck, David H. AU - Yan, Binghai AU - Kronik, Leeor ID - 10771 IS - 13 JF - Advanced Materials SN - 09359648 TI - Theory of chirality induced spin selectivity: Progress and challenges VL - 34 ER - TY - JOUR AB - Rotational dynamics of D2 molecules inside helium nanodroplets is induced by a moderately intense femtosecond pump pulse and measured as a function of time by recording the yield of HeD+ ions, created through strong-field dissociative ionization with a delayed femtosecond probe pulse. The yield oscillates with a period of 185 fs, reflecting field-free rotational wave packet dynamics, and the oscillation persists for more than 500 periods. Within the experimental uncertainty, the rotational constant BHe of the in-droplet D2 molecule, determined by Fourier analysis, is the same as Bgas for an isolated D2 molecule. Our observations show that the D2 molecules inside helium nanodroplets essentially rotate as free D2 molecules. AU - Qiang, Junjie AU - Zhou, Lianrong AU - Lu, Peifen AU - Lin, Kang AU - Ma, Yongzhe AU - Pan, Shengzhe AU - Lu, Chenxu AU - Jiang, Wenyu AU - Sun, Fenghao AU - Zhang, Wenbin AU - Li, Hui AU - Gong, Xiaochun AU - Averbukh, Ilya Sh AU - Prior, Yehiam AU - Schouder, Constant A. AU - Stapelfeldt, Henrik AU - Cherepanov, Igor AU - Lemeshko, Mikhail AU - Jäger, Wolfgang AU - Wu, Jian ID - 11552 IS - 24 JF - Physical Review Letters SN - 00319007 TI - Femtosecond rotational dynamics of D2 molecules in superfluid helium nanodroplets VL - 128 ER - TY - JOUR AB - 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. AU - Brauneis, Fabian AU - Backert, Timothy G. AU - Mistakidis, Simeon I. AU - Lemeshko, Mikhail AU - Hammer, Hans Werner AU - Volosniev, Artem ID - 11590 IS - 6 JF - New Journal of Physics SN - 1367-2630 TI - Artificial atoms from cold bosons in one dimension VL - 24 ER - TY - JOUR AB - We compare recent experimental results [Science 375, 528 (2022)] of the superfluid unitary Fermi gas near the critical temperature with a thermodynamic model based on the elementary excitations of the system. We find good agreement between experimental data and our theory for several quantities such as first sound, second sound, and superfluid fraction. We also show that mode mixing between first and second sound occurs. Finally, we characterize the response amplitude to a density perturbation: Close to the critical temperature both first and second sound can be excited through a density perturbation, whereas at lower temperatures only the first sound mode exhibits a significant response. AU - Bighin, Giacomo AU - Cappellaro, Alberto AU - Salasnich, L. ID - 11592 IS - 6 JF - Physical Review A SN - 2469-9926 TI - Unitary Fermi superfluid near the critical temperature: Thermodynamics and sound modes from elementary excitations VL - 105 ER - TY - JOUR AB - Recently it became possible to study highly excited rotational states of molecules in superfluid helium through nonadiabatic alignment experiments (Cherepanov et al 2021 Phys. Rev. A 104 L061303). This calls for theoretical approaches that go beyond explaining renormalized values of molecular spectroscopic constants, which suffices when only the lowest few rotational states are involved. As the first step in this direction, here we present a basic quantum mechanical model describing highly excited rotational states of molecules in superfluid helium nanodroplets. We show that a linear molecule immersed in a superfluid can be seen as an effective symmetric top, similar to the rotational structure of radicals, such as OH or NO, but with the angular momentum of the superfluid playing the role of the electronic angular momentum in free molecules. The simple theory sheds light onto what happens when the rotational angular momentum of the molecule increases beyond the lowest excited states accessible by infrared spectroscopy. In addition, the model allows to estimate the effective rotational and centrifugal distortion constants for a broad range of species and to explain the crossover between light and heavy molecules in superfluid 4He in terms of the many-body wavefunction structure. Some of the above mentioned insights can be acquired by analyzing a simple 2 × 2 matrix. AU - Cherepanov, Igor AU - Bighin, Giacomo AU - Schouder, Constant A. AU - Chatterley, Adam S. AU - Stapelfeldt, Henrik AU - Lemeshko, Mikhail ID - 11998 IS - 7 JF - New Journal of Physics SN - 1367-2630 TI - A simple model for high rotational excitations of molecules in a superfluid VL - 24 ER - TY - JOUR AB - We study the fate of an impurity in an ultracold heteronuclear Bose mixture, focusing on the experimentally relevant case of a ⁴¹K - ⁸⁷Rb mixture, with the impurity in a ⁴¹K hyperfine state. Our paper provides a comprehensive description of an impurity in a BEC mixture with contact interactions across its phase diagram. We present results for the miscible and immiscible regimes, as well as for the impurity in a self-bound quantum droplet. Here, varying the interactions, we find exotic states where the impurity localizes either at the center or at the surface of the droplet. AU - Bighin, Giacomo AU - Burchianti, A. AU - Minardi, F. AU - Macrì, T. ID - 11997 IS - 2 JF - Physical Review A SN - 2469-9926 TI - Impurity in a heteronuclear two-component Bose mixture VL - 106 ER - TY - JOUR AB - We demonstrate the formation of robust zero-energy modes close to magnetic impurities in the iron-based superconductor FeSe1-z Tez. We find that the Zeeman field generated by the impurity favors a spin-triplet interorbital pairing as opposed to the spin-singlet intraorbital pairing prevalent in the bulk. The preferred spin-triplet pairing preserves time-reversal symmetry and is topological, as robust, topologically protected zero modes emerge at the boundary between regions with different pairing states. Moreover, the zero modes form Kramers doublets that are insensitive to the direction of the spin polarization or to the separation between impurities. We argue that our theoretical results are consistent with recent experimental measurements on FeSe1-z Tez. AU - Ghazaryan, Areg AU - Kirmani, Ammar AU - Fernandes, Rafael M. AU - Ghaemi, Pouyan ID - 12139 IS - 20 JF - Physical Review B SN - 2469-9950 TI - Anomalous Shiba states in topological iron-based superconductors VL - 106 ER - TY - JOUR AB - Methods inspired from machine learning have recently attracted great interest in the computational study of quantum many-particle systems. So far, however, it has proven challenging to deal with microscopic models in which the total number of particles is not conserved. To address this issue, we propose a variant of neural network states, which we term neural coherent states. Taking the Fröhlich impurity model as a case study, we show that neural coherent states can learn the ground state of nonadditive systems very well. In particular, we recover exact diagonalization in all regimes tested and observe substantial improvement over the standard coherent state estimates in the most challenging intermediate-coupling regime. Our approach is generic and does not assume specific details of the system, suggesting wide applications. AU - Rzadkowski, Wojciech AU - Lemeshko, Mikhail AU - Mentink, Johan H. ID - 12150 IS - 15 JF - Physical Review B SN - 2469-9950 TI - Artificial neural network states for nonadditive systems VL - 106 ER -