Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session UU06: V: General AMO Physics |
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Sponsoring Units: DAMOP Chair: Ivor Kresic, Technical University of Vienna Room: Virtual Room 6 |
Wednesday, March 22, 2023 5:00AM - 5:12AM |
UU06.00001: Improved universal empirical and theoretical fits for K x-ray production cross sections Gregory Lapicki The relevance of x-ray production cross sections (XRPCS) and the related ionization cross sections (ISC) in many research areas has been described at length and analyzed in detail [1]. X-ray emission cross sections by ion impact are a relevant input in many areas such as studies of track structure in biological matter. Particle Induced X-ray Emission (PIXE) strongly requires trustworthy databases for XRPCS and/or reliable predictions of inner-shell ionization theories as periodically evaluated in Monte Carlo Geant4 simulations [2]. |
Wednesday, March 22, 2023 5:12AM - 5:24AM |
UU06.00002: Bidirectional microwave-optical transduction based on bulk acoustic resonators-silicon nitride integrated photonics co-integration Terence Blésin, Wil Kao, Anat Siddharth, Alaina G Attanasio, Hao Tian, Rui N Wang, Sunil A Bhave, Tobias J Kippenberg Coherent interfaces between microwave and optical frequencies are key components to weave networks of quantum systems for communication, sensing and computing. In this context, we will present the experimental characterization of a bidirectional microwave-optical frequency converter based on monolithic integration of piezoelectric actuators on silicon nitride photonic integrated circuits. The silicon substrate is released to confine high-overtone bulk acoustic waves in a silicon oxide cladding, leading to enhanced electromechanical and stress-optic couplings. The optical waveguides are fabricated using the photonic Damascene process, enabling simultaneously tight mode confinement and high quality factors while maintaining flexibility in dispersion engineering. The broadband transduction assisted by multiple acoustic modes paves the way toward the realization of an optically controlled arbitrary waveform generator for quantum applications. |
Wednesday, March 22, 2023 5:24AM - 5:36AM |
UU06.00003: Collective response in light-matter interactions: The interplay between electronic strong coupling and local nuclear dynamics Bingyu Cui, Abraham Nitzan A model designed to mimic the implications of the collective optical response of molecular ensembles in optical cavities on molecular vibronic dynamics is investigated. Strong molecule-radiation field coupling is often reached when a large number N of molecules respond collectively to the radiation field. In electronic strong coupling, molecular nuclear dynamics following polariton excitation reflects (a) the timescale separation between the fast electronic and photonic dynamics and the slow nuclear motion on one hand, and (b) the interplay between the collective nature of the molecule-field coupling and the local nature of the molecules nuclear response on the other. The first implies that the electronic excitation takes place, in the spirit of the Born approximation, at an approximately fixed nuclear configuration. The second can be rephrased as the intriguing question, can the collective nature of the optical excitation lead to collective nuclear motion following polariton formation, resulting in so-called polaron decoupled dynamics. We address this issue by studying the dynamical properties of a simplified Holstein-Tavis-Cummings type model, in which boson modes representing molecular vibrations are replaced by two-level systems while the boson frequency and the vibronic coupling are represented by the coupling between these levels (that induces Rabi oscillations between them) and electronic state dependence of this coupling. We investigate the short-time behavior of this model following polariton excitation as well as its response to CW driving and its density of states spectrum, by truncating into a mathematically trackable Hillbert subspace. We find that, while some aspects of the dynamical behavior appear to adhere to the polaron decoupling picture, the observed dynamics mostly reflect the local nature of the nuclear configuration of the electronic polariton rather than this picture. Invoking classical representation of the radiation field and mean field treatment of the molecular subsystems, the long-time evolution can be attained, recovering the same short-time dynamics in the truncated basis. |
Wednesday, March 22, 2023 5:36AM - 5:48AM |
UU06.00004: Coupling and routing dynamics of interlayer valley excitons in two-dimensional Vanderwall heterostructures via SiN microresonators Kishor K Mandal, Anuj k singh, Brijesh K gangwar, ANSHUMAN KUMAR The presence of a vertical component to the transition dipole moment in interlayer excitons, which suppresses electron-hole overlap, results in longer radiative lifetimes as compared to intralayer excitons. Such tightly bound interlayer excitons well-suited candidates for valley-based quantum information processing applications. Their optical accessibility is, however, limited due to their out-of-plane transition dipole moment. We first design a system to strengthen the coupling of interlayer excitons in two-dimensional (2D) material heterostructures with Purcell enhanced out-of-plane resonant modes of a Whispering Gallery Mode (WGM) resonator at room temperature. The high quantum confinement of light in a small modal volume and high Q-factor allow a much stronger coupling of these excitons to the electromagnetic field. We then discuss how to engineer an asymmetric transmission of light from these excitons, which facilitates readout from such systems. We also present our attempts to experimentally demonstrate the valley selective separation and routing of interlayer excitons in the MoSe2/WSe2 heterobilayer stack of TMDCs material by integrating on a planar silicon nitride (SiN) bus-waveguide coupled with a microring resonator (MRR). |
Wednesday, March 22, 2023 5:48AM - 6:00AM |
UU06.00005: Modeling Phonon-Induced Decoherence in Solid-State Defect based Qubits Prajit Dhara, Saikat Guha Systems that serve as quantum memories are crucial to tasks in quantum information processing, computing, and communication. Decoherence of the electronic spin qubits in solid state defect centers have been studied extensively in experiments and methodologies have been developed to estimate spin decoherence rates. We model the effect of decoherence caused by spin-phonon coupling in these systems, with a special focus on the evolution of the entangled state of two spin qubits that were entangled using a heralded photonic Bell swap. Our model predicts the initial Fidelity and the decay rate of distillable entanglement, which is corroborated by experimentally observed decoherence time scales. Extending our model to include other decoherence mechanisms, e.g., via hyperfine coupling to neighboring nuclear spins, will pave the way to a predictive model for engineering artificial-atom qubits with desirable coherence properties. |
Wednesday, March 22, 2023 6:00AM - 6:12AM |
UU06.00006: Valley-polarized Hyperbolic-Exciton-Polaritons in Few-layer 2D Semiconductors at Visible Frequencies Itai Epstein In this work, we predict the existence of hyperbolic-exciton-polaritons (HEPs) in 2D semiconductors of transition-metal-dichalcogenides (TMDs) at visible frequencies. We show that hyperbolicity can be induced in the layered material owing to the behavior of the excitons supported by the TMD, therefore leading to the existence of HEPs. We derive the HEPs’ dispersion relation under these conditions and analyze their confinement and loss properties, incorporating non-local corrections stemming from the high momentum of the modes. In addition, we show that owing to the valley properties of TMDs, the HEPs are coupled to the valley degree-of-freedom, leading to a hyperbolic spin-valley hall effect. Such highly confined and valley-polarized HEPs provide new opportunities to control strong light-matter interaction at the atomic scale. |
Wednesday, March 22, 2023 6:12AM - 6:24AM |
UU06.00007: Properties of Molecular Exciton-Polaritons: Coupling Ab Initio Calculations with Quantum Optics Braden M Weight, Pengfei Huo Polaritonic chemistry has become the leading direction to control a multitude of processes, such as charge transfer, selective bond breaking, and excited state dynamics. An exciton-polariton is an entangled state of light and matter in which the native excitonic and photonic degrees of freedom hybridize to form new states. These new states can be tuned in various ways to modify and produce unique properties, such as the potential energy landscape or the emission efficiency of materials. However, much is still unknown about how these new hybrid states can modify such chemical properties. For example, the nature of the exciton is lost and becomes effectively mixed with all other molecular excitations, and so the shape and distribution of resulting exciton-polariton wavefunctions will be dramatically different from the uncoupled excitonic picture. These changes will dictate all the resulting properties, such as the absorption/emission spectra though the polaritonic transition dipole moment and the excited state dynamics through modification of the potential energy surfaces. In this work, we explore a set of real, atomistic molecules via density functional theory and couple their electronic structure to a single-mode cavity in order to explore the resulting properties of the coupled system. |
Wednesday, March 22, 2023 6:24AM - 6:36AM |
UU06.00008: Study on the change of the character of Imbert-Fedorov optical beam shift: spatial and angular shifts Niladri Modak Optical beam shifts appear due to diffractive corrections when the beam experiences any tilted interface. Imbert-Fedorov (IF) beam shift is one of such shifts causing transverse deflection of the beam. Taking an example of partial reflection, we study the nature of IF beam shifts, i.e., angular and spatial shifts in different regions of the corresponding parameter space. The different regions of the parameter space showing angular and spatial shifts are demarcated with the possible origin of the corresponding shifts. The transition from spatial to angular shift is discussed. These observations might help to understand the origin of IF shift in more clarity and find connections to other domains of physics. |
Wednesday, March 22, 2023 6:36AM - 6:48AM |
UU06.00009: Phase behaviour of Polydisperse Diblock Copolymers Desiree A Rehel, Anchang Shi, Chi To Lai Recent experimental and theoretical studies have shown that many ordered structures, ranging in complexity from simple lamellae to complex Frank-Kasper (FK) phases, can be formed from diblock copolymers. While most theoretical studies have been based on monodisperse systems, almost all the polymeric samples used in experiments are polydisperse. It is therefore desirable to carry out theoretical studies on the phase behaviour of polydisperse block copolymer systems. In our study, the molecular weight distribution of AB diblock copolymers is modeled as a blend with four components. The effects of the shape of the molecular weight distribution (MWD) are studied by using the self-consistent field theory. It is found that the width and skewness of the MWD, as well as the conformational asymmetry, have significant effects on the formation of the FK phases. The theoretical results shed light on the formation mechanisms of the FK phases and provide insight to regulating block copolymer phase behaviours via designed molecular weight distributions. |
Wednesday, March 22, 2023 6:48AM - 7:00AM |
UU06.00010: Disclination in nematic liquid crystal as superelastic rods Shengzhu Yi, Xinyu Wang, Hao Chen, Rui Zhang, Qihuo Wei Unlike elastic materials, the energies of disclinations in nematic liquid crystal are correlated linearly to their length. Here, based on the Landau-de Gennes phenomenological method, we investigate the elastic behaviour of disclinations confined by two patterned surfaces. By translating and rotating one of the surfaces, the disclinations were stretched and twisted, respectively. Thus, the elastic properties of disclinations can be measured, including line tension, torsional rigidity, shear modulus and effective bending stiffness. The energy of disclinations is determined by their length and the difference in the phase angle of the two surfaces. We observed the bending of stretched disclinations, under twist, from simulations and experimental results validated this coupling behaviour. Under a critical twist angle, the deflections of curved disclinations increases linearly with the twist angle and translate distance. We present a toy model that explains the bend-twist coupling of disclinations, which contains the fourth mechanical parameter, bend-twist coupling g. The bend-twist coupling of disclinations is favoured by the twist distortions of the nematic liquid crystals. These new findings help predicting the dynamic behaviour of disclinations and manipulate the disclinations more intuitively. |
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