@article{21149, abstract = {We present a general theoretical framework for helical dichroism (HD), establishing an explicit link between chiral resolution and orbital angular momentum (OAM) exchange in light–matter interaction. Tracing microscopic mechanisms of the OAM transfer, we derive rotational selection rules, which establish that HD emerges only from the spin–orbit coupling of light, even for beams without the far-field OAM. Our findings refine the conditions for observing HD, provide a tool to re-examine the outcome of prior experiments, and guide future designs for chiral sensing with structured light.}, author = {Hrast, Mateja and Koutentakis, Georgios and Maslov, Mikhail and Lemeshko, Mikhail}, issn = {1079-7114}, journal = {Physical Review Letters}, number = {5}, publisher = {American Physical Society}, title = {{Bottom-up analysis of rovibrational helical dichroism}}, doi = {10.1103/fkf1-1jml}, volume = {136}, year = {2026}, } @article{21273, abstract = {In this paper we examine how porosity fluctuations affect the hydrodynamic permeability of a porous matrix or membrane. We introduce a fluctuating Darcy model, which couples the Navier-Stokes equation to the space- and time-dependent porosity fluctuations via a Darcy friction term. Using a perturbative approach, a Dyson equation for hydrodynamic fluctuations is derived and solved to express the permeability in terms of the matrix fluctuation spectrum. Surprisingly, the model reveals strong modifications of the fluid permeability in fluctuating matrices compared to static ones. Applications to various matrix excitation models, the breathing matrix, phonons, and active forcing, highlight the significant influence of matrix fluctuations on fluid transport, offering insights for optimizing membrane design for separation applications.}, author = {Dombret, Albert and Sutter, Adrien and Coquinot, Baptiste and Kavokine, Nikita and Coasne, Benoit and Bocquet, Lydéric}, issn = {2469-990X}, journal = {Physical Review Fluids}, number = {1}, publisher = {American Physical Society}, title = {{Hydrodynamic permeability of fluctuating porous membranes}}, doi = {10.1103/m8h6-1wfk}, volume = {11}, year = {2026}, } @article{21373, abstract = {Cold atom experiments show that a mobile impurity particle immersed in a weakly interacting Bose-Einstein condensate forms a well-defined quasiparticle (Bose polaron) for weak to moderate impurity-boson interaction strengths, whereas a significant line broadening is consistently observed for strong interactions. Motivated by this, we introduce a phenomenological theory based on the assumption that the most relevant states are characterized by the impurity correlated with at most one boson, since they have the largest overlap with the uncorrelated states to which the most common experimental probes couple. These experimentally relevant states can, however, decay to lower energy states characterized by correlations involving multiple bosons, and we model this using a minimal variational wave function combined with a complex impurity-boson interaction strength. We first motivate this approach by comparing to a more elaborate theory that includes correlations with up to two bosons. Our phenomenological model is shown to recover the main results of two recent experiments probing both the spectral and the nonequilibrium properties of the Bose polaron. Our work offers an intuitive framework for analyzing experimental data and highlights the importance of understanding the complicated problem of the Bose polaron decay in a many-body setting.}, author = {Al Hyder, Ragheed and Bruun, G. M. and Pohl, T. and Lemeshko, Mikhail and Volosniev, Artem}, issn = {2643-1564}, journal = {Physical Review Research}, publisher = {American Physical Society}, title = {{Phenomenological model of decaying Bose polarons}}, doi = {10.1103/16dk-5dgx}, volume = {8}, year = {2026}, } @article{21009, abstract = {We demonstrate that periodically driven quantum rotors provide a promising and broadly applicable platform to implement multigap topological phases, where groups of bands can acquire topological invariants due to non-Abelian braiding of band degeneracies. By adiabatically varying the periodic kicks to the rotor we find nodal-line braiding, which causes sign flips of topological charges of band nodes and can prevent them from annihilating, indicated by nonzero values of the patch Euler class. In particular, we report on the emergence of an anomalous Dirac string phase arising in the strongly driven regime, a truly out-of-equilibrium phase of the quantum rotor. This phase emanates from braiding processes involving all (quasienergy) gaps and manifests itself with edge states at zero angular momentum. Our results reveal direct applications in state-of-the-art experiments of quantum rotors, such as linear molecules driven by periodic far-off-resonant laser pulses or artificial quantum rotors in optical lattices, whose extensive versatility offers precise modification and observation of novel non-Abelian topological properties.}, author = {Karle, Volker and Lemeshko, Mikhail and Bouhon, Adrien and Slager, Robert-Jan and Ünal, F. Nur}, issn = {2469-9934}, journal = {Physical Review A}, number = {1}, publisher = {American Physical Society}, title = {{Anomalous multigap topological phases in periodically driven quantum rotors}}, doi = {10.1103/db9d-9bns}, volume = {113}, year = {2026}, } @article{21470, abstract = {Despite its pivotal role in optical manipulation, high capacity communications, and quantum information, a general measure of orbital angular momentum (OAM) in structured light remains elusive. In optical fields, where multiple vortices coexist, the local nature of vortex OAM and the absence of a common rotation axis make the total OAM of the field difficult to quantify. Here, we introduce the R index—a metric that captures the intrinsic OAM content of any structured optical field, from pure Laguerre–Gaussian modes to arbitrary multi vortex superpositions. Not only does this metric quantify the total OAM, it also assesses field purity, providing insight into the fidelity and robustness of the OAM generation. By unifying OAM characterization into a single figure of merit, the R index enables direct comparison across diverse beam profiles and facilitates the identification of optimal configurations for both foundational studies and applied technologies.}, author = {Bahl, Monika and Koutentakis, Georgios and Maslov, Mikhail and Jungnickel, Tom and Gaßen, Timo and Lemeshko, Mikhail and Heckl, Oliver H.}, issn = {2515-7647}, journal = {Journal of Physics: Photonics}, number = {1}, publisher = {IOP Publishing}, title = {{The R-index: A universal metric for evaluating OAM content and mode purity in optical fields}}, doi = {10.1088/2515-7647/ae3506}, volume = {8}, year = {2026}, } @article{21660, abstract = {Kapitza-Dirac scattering, the diffraction of matter waves from a standing light field, is widely utilized in ultracold gases, but its behavior in the strongly interacting regime is an open question. Here, we develop a numerically exact two-body description of Kapitza-Dirac scattering for two contact-interacting atoms in a one-dimensional harmonic trap subjected to a pulsed optical lattice, enabling us to obtain the numerically exact dynamics. We map how interaction strength, lattice depth, lattice wave number, and pulse duration reshape the diffraction pattern, leading to an interaction-dependent population redistribution in real and momentum space. By comparing the exact dynamics to an impulsive sudden-approximation description, we delineate the parameter regimes where it remains accurate and those, notably at strong attraction and small lattice wave number, where it fails. Our results provide a controlled few-body benchmark for interacting Kapitza-Dirac scattering and quantitative guidance for Kapitza-Dirac-based probes of ultracold atomic systems.}, author = {Becker, A. and Koutentakis, Georgios and Schmelcher, P.}, issn = {2643-1564}, journal = {Physical Review Research}, publisher = {American Physical Society}, title = {{Two-body Kapitza-Dirac scattering of one-dimensional ultracold atoms}}, doi = {10.1103/rdsn-stlq}, volume = {8}, year = {2026}, } @article{21840, abstract = {The transport properties of nanofluidic channels are usually studied under constant (DC) voltage or pressure driving. However, the frequency response under sinusoidal (AC) drivings offers rich insights into the time-dependent transport mechanisms. Inspired by recent electrochemical approaches, we investigate the couplings between ionic and electronic transport under AC driving. We show that conduction electrons of the channel walls participate in ionic current via capacitive electrochemical coupling, defining a critical frequency and length scale where electron-dominated conductivity emerges. We further analyze how electron–ion coupling modifies electro-osmotic flows and demonstrate that fluctuation-induced momentum transfer between the electrolyte and wall electrons produces distinct AC transport signatures, depending on the charge carrier polarity. Altogether, we establish a frequency-dependent transport matrix that couples ionic, electronic, and hydrodynamic flows. These findings establish AC nanofluidic transport as a powerful probe of interfacial phenomena under confinement and suggest new directions for engineering nanofluidic functionalities through electron–electrolyte coupling.}, author = {Coquinot, Baptiste and Lizée, Mathieu and Bocquet, Lydéric and Kavokine, Nikita}, issn = {1089-7690}, journal = {The Journal of Chemical Physics}, number = {13}, publisher = {AIP Publishing}, title = {{Electron–electrolyte coupling in AC transport through nanofluidic channels}}, doi = {10.1063/5.0313352}, volume = {164}, year = {2026}, } @article{18710, abstract = {We present an ab initio theoretical method to calculate the resonant Auger spectrum in the presence of ultrafast dissociation. The method is demonstrated by deriving the L-VV resonant Auger spectrum mediated by the 2p3/2−1σ* resonance in HCl, where the electronic Auger decay and nuclear dissociation occur on the same time scale. The Auger decay rates are calculated within the one-center approximation and are shown to vary significantly with the inter-nuclear distance. A quantum-mechanical description of dissociation is effectuated by propagating the corresponding Franck–Condon factors. The calculated profiles of Auger spectral lines resemble those of atomic Auger decay but here the characteristic tails extend towards lower electron kinetic energies, which reflect specific features of the potential energy curves. The presented method can describe the resonant Auger spectrum for an arbitrary speed of dissociation and simplifies to known approximations in the limiting cases.}, author = {Hrast, Mateja and Ljubotina, Marko and Zitnik, Matjaz}, issn = {1463-9076}, journal = {Physical Chemistry Chemical Physics}, number = {3}, pages = {1473--1482}, publisher = {Royal Society of Chemistry}, title = {{Ab initio Auger spectrum of the ultrafast dissociating 2p3/2−1σ* resonance in HCl}}, doi = {10.1039/d4cp03727h}, volume = {27}, year = {2025}, } @article{19880, abstract = {We investigate quantum transport in a two-dimensional electron system coupled to a chiral molecular potential, demonstrating how molecular chirality and orientation affect charge and spin transport properties. We propose a minimal model for realizing true chiral symmetry breaking on a magnetized surface, with a crucial role played by the tilt angle of the molecular dipole with respect to the surface. For non-zero tilting, we show that the Hall response exhibits clear signatures of chirality-induced effects, in both charge- and spin-resolved observables. Concerning the former, tilted enantiomers produce asymmetric Hall conductances and, even more remarkably, the persistence of this feature in the absence of spin–orbit coupling (SOC) signals how the enantiospecific charge response results from electron scattering off the molecular potential. Concerning spin-resolved observables where SOC plays a relevant role, we reveal that chiral symmetry breaking is crucial in enabling spin-flipping processes.}, author = {Al Hyder, Ragheed and Lemeshko, Mikhail and Cappellaro, Alberto}, issn = {1089-7690}, journal = {The Journal of Chemical Physics}, number = {23}, publisher = {AIP Publishing}, title = {{Quantum transport in the presence of a chiral molecular potential}}, doi = {10.1063/5.0271155}, volume = {162}, year = {2025}, } @article{20003, abstract = {The problem of mobile impurities in quantum baths is of fundamental importance in many-body physics. There has recently been significant progress regarding our understanding of this due to cold atom experiments, but so far it has mainly been concerned with cases where the bath has no or only weak interactions, or the impurity interacts weakly with the bath. Here, we address this gap by developing a new theoretical framework for exploring a mobile impurity interacting strongly with a highly correlated bath of bosons in the quantum critical regime of a Mott insulator (MI) to superfluid (SF) quantum phase transition. Our framework is based on a powerful quantum Gutzwiller (QGW) description of the bosonic bath combined with diagrammatic field theory for the impurity-bath interactions. By resumming a selected class of diagrams to infinite order, a rich picture emerges where the impurity is dressed by the fundamental modes of the bath, which change character from gapped particle-hole excitations in the MI to Higgs and gapless Goldstone modes in the SF. This gives rise to the existence of several quasiparticle (polaron) branches with properties reflecting the strongly correlated environment. In particular, one polaron branch exhibits a sharp cusp in its energy, while a new ground-state polaron emerges at the O(2) quantum phase transition point for integer filling, which reflects the nonanalytic behavior at the transition and the appearance of the Goldstone mode in the SF phase. Smooth versions of these features are inherited in the polaron spectrum away from integer filling due to the influence of Mott physics on the bosonic bath. We furthermore compare our diagrammatic results with quantum Monte Carlo calculations, obtaining excellent agreement. This accuracy is quite remarkable for such a highly non-trivial case of strong interactions between the impurity and bosons in a maximally correlated quantum critical regime, and it establishes the utility of our framework. Finally, our results show how impurities can be used as quantum sensors and highlight fundamental differences between experiments performed at a fixed particle number or a fixed chemical potential.}, author = {Al Hyder, Ragheed and Colussi, Victor E. and Čufar, Matija and Brand, Joachim and Recati, Alessio and Bruun, Georg M.}, issn = {2542-4653}, journal = {Scipost Physics}, number = {1}, publisher = {SciPost Foundation}, title = {{Lattice Bose polarons at strong coupling and quantum criticality}}, doi = {10.21468/SciPostPhys.19.1.002}, volume = {19}, year = {2025}, } @article{20405, abstract = {Dielectric breakdown of physical vacuum (Schwinger effect) is the textbook demonstration of compatibility of Relativity and Quantum theory. Although observing this effect is still practically unachievable, its analogue generalizations have been shown to be more readily attainable. This paper demonstrates that a gapped Dirac semiconductor, methylammonium lead-bromide perovskite (MAPbBr3), exhibits analogue dynamic Schwinger effect. Tunneling ionization under deep subgap mid-infrared irradiation leads to intense photoluminescence in the visible range, in full agreement with quasi-adiabatic theory. In addition to revealing a gapped extended system suitable for studying the analogue Schwinger effect, this observation holds great potential for nonperturbative field sensing, i.e., sensing electric fields through nonperturbative light-matter interactions. First, this paper illustrates this by measuring the local deviation from the nominally cubic phase of a perovskite single crystal, which can be interpreted in terms of frozen-in fields. Next, it is shown that analogue dynamic Schwinger effect can be used for nonperturbative amplification of nonparametric upconversion process in perovskites driven simultaneously by multiple optical fields. This discovery demonstrates the potential for material response beyond perturbation theory in the tunneling regime, offering extremely sensitive light detection and amplification across an ultrabroad spectral range not accessible by conventional devices.}, author = {Lorenc, Dusan and Volosniev, Artem and Zhumekenov, Ayan A. and Lee, Seungho and Ibáñez, Maria and Bakr, Osman M. and Lemeshko, Mikhail and Alpichshev, Zhanybek}, issn = {2330-4022}, journal = {ACS Photonics}, number = {9}, pages = {5220--5230}, publisher = {American Chemical Society}, title = {{Observation of analogue dynamic Schwinger effect and non-perturbative light sensing in lead halide perovskites}}, doi = {10.1021/acsphotonics.5c01360}, volume = {12}, year = {2025}, } @article{20432, abstract = {A rapidly increasing body of work reporting phenomena associated with lattice vibrations carrying angular momentum has led to the emergence of the field of chiral phonons. Some of these properties, such as the phonon magnetic moment, also occur in achiral phonons that are circularly or elliptically polarized, while the presence of chirality has additional implications for the types of interaction allowed between the phonons and light, electrons and other quasiparticles. In this Perspective we introduce a framework for classifying phonons with angular momentum, and provide illustrations of the different types using examples from the recent literature. Specifically, we suggest the term ‘axial phonon’ to encompass all phonons that carry angular momentum, real or pseudo, and reserve the term ‘chiral phonon’ for those phonons that break improper rotational symmetry. We hope that this scheme provides clarification on the matter of phonon chirality and will serve as a guide for future research.}, author = {Juraschek, Dominik M. and Geilhufe, R. Matthias and Zhu, Hanyu and Basini, Martina and Baum, Peter and Baydin, Andrey and Chaudhary, Swati and Fechner, Michael and Flebus, Benedetta and Grissonnanche, Gael and Kirilyuk, Andrei I. and Lemeshko, Mikhail and Maehrlein, Sebastian F. and Mignolet, Maxime and Murakami, Shuichi and Niu, Qian and Nowak, Ulrich and Romao, Carl P. and Rostami, Habib and Satoh, Takuya and Spaldin, Nicola A. and Ueda, Hiroki and Zhang, Lifa}, issn = {1745-2481}, journal = {Nature Physics}, pages = {1532--1540}, publisher = {Springer Nature}, title = {{Chiral phonons}}, doi = {10.1038/s41567-025-03001-9}, volume = {21}, year = {2025}, } @article{20666, abstract = {We theoretically investigate the stationary properties of a spin-1/2 impurity immersed in a one-dimensional confined Bose gas. In particular, we consider coherently coupled spin states with an external field, where only one spin component interacts with the bath, enabling light dressing of the impurity and spin-dependent bath-impurity interactions. Through detailed comparisons with ab-initio many-body simulations, we demonstrate that the composite system is accurately described by a simplified effective Hamiltonian. The latter builds upon previously developed effective potential approaches in the absence of light dressing. It can be used to extract the impurity energy, residue, effective mass, and anharmonicity induced by the phononic dressing. Light-dressing is shown to increase the polaron residue, undressing the impurity from phononic excitations because of strong spin coupling. For strong repulsions, previously shown to trigger dynamical Bose polaron decay (a phenomenon called temporal orthogonality catastrophe), it is explained that strong light-dressing stabilizes a repulsive polaron-dressed state. Our results establish the effective Hamiltonian framework as a powerful tool for exploring strongly interacting polaronic systems and corroborating forthcoming experimental realizations.}, author = {Koutentakis, Georgios and Mistakidis, S. I. and Grusdt, F. and Sadeghpour, H. R. and Schmelcher, P.}, issn = {2542-4653}, journal = {Scipost Physics}, number = {4}, publisher = {SciPost Foundation}, title = {{Competition of light-and phonon-dressing in microwave-dressed Bose polarons}}, doi = {10.21468/SciPostPhys.19.4.093}, volume = {19}, year = {2025}, } @article{20732, abstract = {We investigate the real-time dynamics of a quenched quantum impurity immersed in a one-dimensional ultracold Fermi gas, focusing on the breakdown of the adiabatic Born-Oppenheimer approximation due to nonadiabatic effects. Despite a sizable impurity-bath mass imbalance, increasing interactions induce strong nonadiabatic couplings, disrupting adiabatic motion and enabling population transfer between the adiabatic potential energy curves. These transitions are governed by conical intersections arising from the pseudo Jahn-Teller effect, dynamically shaping the impurity's motion through the bath. Using ab initio simulations via the multilayer multiconfiguration time-dependent Hartree method and a multichannel Born-Oppenheimer framework, we track the impurity's evolution and directly prove the dynamical manifestation of the pseudo Jahn-Teller effect. We analyze two key scenarios: (i) a small initial shift, where a single avoided crossing drives transitions, and (ii) a large shift, where multiple avoided crossings lead to enhanced nonadiabaticity, self-trapping, and energy redistribution. Our findings establish ultracold fermionic few-body systems as tunable platforms for studying nonadiabatic quantum dynamics, opening new avenues for controlled impurity transport in strongly correlated environments.}, author = {Becker, A. and Koutentakis, Georgios and Schmelcher, P.}, issn = {2643-1564}, journal = {Physical Review Research}, number = {3}, publisher = {American Physical Society}, title = {{Dynamical probe of the pseudo Jahn-Teller effect in one-dimensional confined fermions}}, doi = {10.1103/2fr6-b59y}, volume = {7}, year = {2025}, } @article{18821, abstract = {Even though the one-dimensional contact interaction requires no regularization, renormalization methods have been shown to improve the convergence of numerical calculations considerably. In this work, we compare and contrast these methods: “the running coupling constant” where the two-body ground-state energy is used as a renormalization condition, and two effective interaction approaches that include information about the ground as well as excited states. In particular, we calculate the energies and densities of few-fermion systems in a harmonic oscillator with the configuration-interaction method and compare the results based upon renormalized and bare interactions. We find that the use of the running coupling constant instead of the bare interaction improves convergence significantly. A comparison with an effective interaction, which is designed to reproduce the relative part of the energy spectrum of two particles, showed a similar improvement. The effective interaction provides an additional improvement if the center-of-mass excitations are included in the construction. Finally, we discuss the transformation of observables alongside the renormalization of the potential, and demonstrate that this might be an essential ingredient for accurate numerical calculations.}, author = {Brauneis, Fabian and Hammer, Hans Werner and Reimann, Stephanie M. and Volosniev, Artem}, issn = {2469-9934}, journal = {Physical Review A}, number = {1}, publisher = {American Physical Society}, title = {{Comparison of renormalized interactions using one-dimensional few-body systems as a testbed}}, doi = {10.1103/PhysRevA.111.013303}, volume = {111}, year = {2025}, } @article{19276, abstract = {Impurity motion in a many-body environment has been a central issue in the field of low-temperature physics for decades. In bosonic quantum fluids, the onset of a drag force experienced by point-like objects is due to collective environment excitations, driven by the exchange of linear momentum between the impurity and the many-body bath. In this work we consider a rotating impurity, with the aim of exploring how angular momentum is exchanged with the surrounding bosonic environment. In order to elucidate these issues, we employ a quasiparticle approach based on the angulon theory, which allows us to effectively deal with the non-trivial algebra of quantized angular momentum in the presence of a many-body environment. We uncover how impurity dressing by environmental excitations can establish an exchange channel, whose effectiveness crucially depends on the initial state of the impurity. Remarkably, we find that there is a critical value of initial angular momentum, above which this channel effectively freezes.}, author = {Cappellaro, Alberto and Bighin, Giacomo and Cherepanov, Igor and Lemeshko, Mikhail}, issn = {1089-7690}, journal = {Journal of Chemical Physics}, number = {7}, publisher = {AIP Publishing}, title = {{Environment-limited transfer of angular momentum in Bose liquids}}, doi = {10.1063/5.0253451}, volume = {162}, year = {2025}, } @article{19371, abstract = {We investigate a molecular quantum rotor in a two-dimensional Bose-Einstein condensate. The focus is on studying the angulon quasiparticle concept in the crossover from few- to many-body physics. To this end, we formulate the problem in real space and solve it with a mean-field approach in the frame co-rotating with the impurity. We show that the system starts to feature angulon characteristics when the size of the bosonic cloud is large enough to screen the rotor. More importantly, we demonstrate the departure from the angulon picture for large system sizes or large angular momenta where the properties of the system are determined by collective excitations of the Bose gas.}, author = {Suchorowski, Michał and Badamshina, Alina and Lemeshko, Mikhail and Tomza, Michał and Volosniev, Artem}, issn = {2542-4653}, journal = {SciPost Physics}, number = {2}, publisher = {SciPost Foundation}, title = {{Quantum rotor in a two-dimensional mesoscopic Bose gas}}, doi = {10.21468/SciPostPhys.18.2.059}, volume = {18}, year = {2025}, } @article{19437, abstract = {We demonstrate the formation of ferroelectric domain-wall polarons in a minimal two-dimensional lattice model of electrons interacting with rotating dipoles. Along the domain wall, the rotors polarize in opposite directions, causing the electron to localize along a particular lattice direction. The rotor-electron coupling is identified as the origin of a structural instability in the crystal that leads to the domain-wall formation via a symmetry-breaking process. Our results provide the first theoretical description of ferroelectric polarons, as discussed in the context of soft semiconductors.}, author = {Kluibenschedl, Florian and Koutentakis, Georgios and Al Hyder, Ragheed and Lemeshko, Mikhail}, issn = {1079-7114}, journal = {Physical Review Letters}, number = {9}, publisher = {American Physical Society}, title = {{Domain-wall ferroelectric polarons in a two-dimensional rotor lattice model}}, doi = {10.1103/PhysRevLett.134.096302}, volume = {134}, year = {2025}, } @article{19502, abstract = {Alkali dimers, Ak2, located on the surface of a helium nanodroplet, are set into rotation through the polarizability interaction with a nonresonant 1-ps-long laser pulse. The time-dependent degree of alignment is recorded using femtosecond-probe-pulse-induced Coulomb explosion into a pair of Ak+ fragment ions. The results, obtained for Na2, K2, and Rb2 in both the ground state 11Σ+g and the lowest-lying triplet state 13Σ+u, exhibit distinct, periodic revivals with a gradually decreasing amplitude. The dynamics differ from that expected for dimers had they behaved as free rotors. Numerically, we solve the time-dependent rotational Schrödinger equation, including an effective mean-field potential to describe the interaction between the dimer and the droplet. The experimental and simulated alignment dynamics agree well and their comparison enables us to determine the effective rotational constants of the alkali dimers with the exception of Rb2(13Σ+u) that only exhibits a prompt alignment peak but no subsequent revivals. For Na2(13Σ+u), K2(11Σ+g), K2(13Σ+u) and Rb2(11Σ+g), the alignment dynamics are well-described by a 2D rotor model. We ascribe this to a significant confinement of the internuclear axis of these dimers, induced by the orientation-dependent droplet-dimer interaction, to the tangential plane of their residence point on the droplet.}, author = {Kristensen, Henrik H. and Kranabetter, Lorenz and Ghazaryan, Areg and Schouder, Constant A. and Hansen, Emil and Jensen, Frank and Zillich, Robert E. and Lemeshko, Mikhail and Stapelfeldt, Henrik}, issn = {2469-9934}, journal = {Physical Review A}, number = {3}, publisher = {American Physical Society}, title = {{Nonadiabatic laser-induced alignment dynamics of alkali-metal dimers on the surface of a helium droplet}}, doi = {10.1103/PhysRevA.111.033114}, volume = {111}, year = {2025}, } @phdthesis{19393, abstract = {Rotations constitute one of the fundamental symmetries in physics, characterized by their intricate group structure and infinite dimensional representations. In contrast to classical rotations, quantum mechanics unveils the SO(3) symmetry group structure, manifesting in phenomena without classical counterparts, from angular momentum quantization to non-trivial addition of angular momenta. While most studies of topological physics have focused on two-band systems, the SO(3) symmetry group of quantum rotors offers an inherently more complex platform with unprecedented possibilities for exploring topological phenomena. Despite their ubiquity in nature– from molecules to nanorotors– their potential for hosting topological phases has remained largely unexamined. In this thesis, we mainly focus on periodically driven linear molecules as a prototype for studying topological phenomena in quantum rotors. Recent technological advances in coherent control of molecules, particularly through precisely shaped laser pulses, have made it possible to investigate linear rotors in the context of topology. While planar rotors have received some attention in recent years, threedimensional rotors–particularly linear molecules–harbor substantially richer topological phenomena due to their non-abelian nature and their additional angular degrees of freedom. We demonstrate that these systems can host novel edge states and topological features fundamentally impossible in planar systems. We begin by establishing a theoretical bridge between periodically kicked rotors and "crystalline" lattices in angular momentum space. Using non-interacting linear molecules as our primary example, we show how quantum interference and revival patterns lead to the possibility to simulate band models with arbitrary number of bands N. While our framework applies to various quantum rotors, including nanorotors and kicked Bose-Einstein condensates, linear molecules provide an ideal experimental platform due to their abovementioned precise controllability. The core of this work examines adiabatic dynamics of 3D quantum rotors, establishing a geometric framework based on the Euler class to characterize its non-abelian topology. The non-Hermitian nature of the system enables novel braiding behaviors and topological transitions impossible in static systems, leading to an anomalous Dirac string phase with edge states in each gap, even though the Berry phases are all zero. These features can be directly observed through molecular alignment and rotational level populations. These findings establish quantum rotors as an alternative platform for studying multi-band topological physics, while suggesting practical implementations for quantum computation where topological protection could offer natural resilience against decoherence. The rich structure of three-dimensional rotation groups, combined with the tunability of topological features through driving parameters, makes this platform particularly valuable for exploring fundamental physics and developing quantum technologies.}, author = {Karle, Volker}, issn = {2663-337X}, pages = {192}, publisher = {Institute of Science and Technology Austria}, title = {{Non-equilibrium topological phases with periodically driven molecules and quantum rotors}}, doi = {10.15479/AT-ISTA-19393}, year = {2025}, }