Physics Commons^™

Advanced Thermoluminescence Spectroscopy As A Research Tool For Semiconductor And Photonic Materials: A Review And Perspective, Farida Selim

Physics and Astronomy Faculty Publications

Thermoluminescence (TL) or thermally stimulated luminescence (TSL) spectroscopy is based on liberating charge carriers from traps in the bandgap by providing enough thermal energy to overcome the potential barrier of the traps. It provides a powerful tool to measure the positions of the localized states/traps in the bandgap. Despite that, its applications in semiconductors are very limited. Herein, the basics of TL spectroscopy and the recent advances in the technique with focus on cryogenic thermally stimulated photoemission spectroscopy (C-TSPS) which extends TL measurements to cryogenic regime and allows the detection of very low concentrations of shallow and deep localized states …

Boost The Lead Conversion Efficiency For The Synthesis Of Colloidal 2d Pbs Nanosheets, Tharaka Mds Weeraddana, Adam Roach, Shashini M. Premathilaka, Yiteng Tang, Jordan Fox, Liangfeng Sun

Physics and Astronomy Faculty Publications

In the synthesis of colloidal PbS nanosheets, the supernatant of the reaction solution is reused to boost the lead conversion efficiency. It doubles the conversion efficiency of the lead precursors to the PbS nanosheets. The nanosheets synthesized by reusing the supernatant have similar morphology, nearly identical thickness, and optical properties as the original ones, confirmed by transmission electron microscopy, X-ray diffraction, and photoluminescence spectroscopy. This method reduces the toxic Pb-containing waste during the synthesis, a step toward the green and scalable synthesis of colloidal 2D PbS nanosheets.

3d Flow Field Measurements Outside Nanopores, Jeffrey Mc Hugh, Alice L. Thorneywork, Kurt Andresen, Ulrich F. Keyser

Physics and Astronomy Faculty Publications

We demonstrate a non-stereoscopic, video-based particle tracking system with optical tweezers to study fluid flow in 3D in the vicinity of glass nanopores. In particular, we used the quadrant interpolation algorithm to extend our video-based particle tracking to displacements out of the trapping plane of the tweezers. This permitted the study of flow from nanopores oriented at an angle to the trapping plane, enabling the mounting of nanopores on a micromanipulator with which it was then possible to automate the mapping procedure. Mapping of the voltage driven flow in 3D volumes outside nanopores revealed polarity dependent flow fields. This is …

Neutron Stars With Baryon Number Violation, Probing Dark Sectors, Jeffrey M. Berryman, Susan Gardner, Mohammadreza Zakeri

Physics and Astronomy Faculty Publications

The neutron lifetime anomaly has been used to motivate the introduction of new physics with hidden-sector particles coupled to baryon number, and on which neutron stars provide powerful constraints. Although the neutron lifetime anomaly may eventually prove to be of mundane origin, we use it as motivation for a broader review of the ways that baryon number violation, be it real or apparent, and dark sectors can intertwine and how neutron star observables, both present and future, can constrain them.

Atomistic Engineering Of Phonons In Functional Oxide Heterostructures, Seung Gyo Jeong, Ambrose Seo, Woo Seok Choi

Physics and Astronomy Faculty Publications

Engineering of phonons, that is, collective lattice vibrations in crystals, is essential for manipulating physical properties of materials such as thermal transport, electron-phonon interaction, confinement of lattice vibration, and optical polarization. Most approaches to phonon-engineering have been largely limited to the high-quality heterostructures of III–V compound semiconductors. Yet, artificial engineering of phonons in a variety of materials with functional properties, such as complex oxides, will yield unprecedented applications of coherent tunable phonons in future quantum acoustic devices. In this study, artificial engineering of phonons in the atomic-scale SrRuO₃/SrTiO₃ superlattices is demonstrated, wherein tunable phonon modes are observed …

Comments On The Holographic Description Of Narain Theories, Anatoly Dymarsky, Alfred D. Shapere

Physics and Astronomy Faculty Publications

We discuss the holographic description of Narain U(1)^c × U(1)^c conformal field theories, and their potential similarity to conventional weakly coupled gravitational theories in the bulk, in the sense that the effective IR bulk description includes “U(1) gravity” amended with additional light degrees of freedom. Starting from this picture, we formulate the hypothesis that in the large central charge limit the density of states of any Narain theory is bounded by below by the density of states of U(1) gravity. This immediately implies that the maximal value of the spectral gap for primary fields is ∆₁ = …

The Measure Aspect Of Quantum Uncertainty, Of Entanglement, And The Associated Entropies, Ivan Horváth

Physics and Astronomy Faculty Publications

Indeterminacy associated with the probing of a quantum state is commonly expressed through spectral distances (metric) featured in the outcomes of repeated experiments. Here, we express it as an effective amount (measure) of distinct outcomes instead. The resulting μ-uncertainties are described by the effective number theory whose central result, the existence of a minimal amount, leads to a well-defined notion of intrinsic irremovable uncertainty. We derive μ-uncertainty formulas for arbitrary set of commuting operators, including the cases with continuous spectra. The associated entropy-like characteristics, the μ-entropies, convey how many degrees of freedom are effectively involved in a given …

The Design Of The N2edm Experiment, N. J. Ayres, G. Ban, L. Bienstman, G. Bison, K. Bodek, V. Bondar, T. Bouillaud, E. Chanel, J. Chen, P.-J. Chiu, B. Clément, C. B. Crawford, M. Daum, B. Dechenaux, C. B. Doorenbos, S. Emmenegger, L. Ferraris-Bouchez, M. Fertl, A. Fratangelo, P. Flaux

Physics and Astronomy Faculty Publications

We present the design of a next-generation experiment, n2EDM, currently under construction at the ultracold neutron source at the Paul Scherrer Institute (PSI) with the aim of carrying out a high-precision search for an electric dipole moment of the neutron. The project builds on experience gained with the previous apparatus operated at PSI until 2017, and is expected to deliver an order of magnitude better sensitivity with provision for further substantial improvements. An overview is of the experimental method and setup is given, the sensitivity requirements for the apparatus are derived, and its technical design is described.

Theoretical Study On Η′ → Π+Π−Π+(0)Π−(0), Ehsan Jafari, Bing An Li

Physics and Astronomy Faculty Publications

The η′ meson is associated with the U(1) anomaly. In this paper, a successful effective chiral theory of mesons has been applied to study the anomalous decays of η′ → π⁺π⁻π⁺⁽⁰⁾π⁻⁽⁰⁾. Contribution of triangle and box diagrams is calculated, which indicates that the box anomaly has a significant contribution to the decay amplitudes.

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Gauge Invariant Target Space Entanglement In D-Brane Holography, Sumit R. Das, Anurag Kaushal, Sinong Liu, Gautam Mandal, Sandip P. Trivedi

Physics and Astronomy Faculty Publications

It has been suggested in arXiv:2004.00613 that in Dp-brane holography, entanglement in the target space of the D-brane Yang-Mills theory provides a precise notion of bulk entanglement in the gravity dual. We expand on this discussion by providing a gauge invariant characterization of operator sub-algebras corresponding to such entanglement. This is achieved by finding a projection operator which imposes a constraint characterizing the target space region of interest. By considering probe branes in the Coloumb branch we provide motivation for why the operator sub-algebras we consider are appropriate for describing a class of measurements carried out with low-energy probes in …

Quantum Stabilizer Codes, Lattices, And Cfts, Anatoly Dymarsky, Alfred D. Shapere

Physics and Astronomy Faculty Publications

There is a rich connection between classical error-correcting codes, Euclidean lattices, and chiral conformal field theories. Here we show that quantum error-correcting codes, those of the stabilizer type, are related to Lorentzian lattices and non-chiral CFTs. More specifically, real self-dual stabilizer codes can be associated with even self-dual Lorentzian lattices, and thus define Narain CFTs. We dub the resulting theories code CFTs and study their properties. T-duality transformations of a code CFT, at the level of the underlying code, reduce to code equivalences. By means of such equivalences, any stabilizer code can be reduced to a graph code. We can …

Magnetic Normal Mode Calculations In Big Systems: A Highly Scalable Dynamical Matrix Approach Applied To A Fibonacci-Distorted Artificial Spin Ice, Loris Giovannini, Barry W. Farmer, Justin S. Woods, Ali Frotanpour, Lance E. De Long, Federico Montoncello

Physics and Astronomy Faculty Publications

We present a new formulation of the dynamical matrix method for computing the magnetic normal modes of a large system, resulting in a highly scalable approach. The motion equation, which takes into account external field, dipolar and ferromagnetic exchange interactions, is rewritten in the form of a generalized eigenvalue problem without any additional approximation. For its numerical implementation several solvers have been explored, along with preconditioning methods. This reformulation was conceived to extend the study of magnetization dynamics to a broader class of finer-mesh systems, such as three-dimensional, irregular or defective structures, which in recent times raised the interest among …

Flavor-Dependent Radiative Corrections In Coherent Elastic Neutrino-Nucleus Scattering, Oleksandr Tomalak, Pedro Machado, Vishvas Pandey, Ryan Plestid

Physics and Astronomy Faculty Publications

We calculate coherent elastic neutrino-nucleus scattering cross sections on spin-0 nuclei (e.g. ⁴⁰Ar and ²⁸Si) at energies below 100 MeV within the Standard Model and account for all effects of permille size. We provide a complete error budget including uncertainties at nuclear, nucleon, hadronic, and quark levels separately as well as perturbative error. Our calculation starts from the four-fermion effective field theory to explicitly separate heavy-particle mediated corrections (which are absorbed by Wilson coefficients) from light-particle contributions. Electrons and muons running in loops introduce a non- trivial dependence on the momentum transfer due to their relatively light masses. …

Ir Finite S-Matrix By Gauge Invariant Dressed States, Hayato Hirai, Sotaro Sugishita

Physics and Astronomy Faculty Publications

Dressed states were proposed to define the infrared (IR) finite S-matrix in QED or gravity. We show that the original Kulish-Faddeev dressed states are not enough to cure the IR divergences. To illustrate this problem, we consider QED with background currents (Wilson lines). This theory is exactly solvable but shares the same IR problems as the full QED. We show that naive asymptotic states lead to IR divergences in the S-matrix and are also inconsistent with the asymptotic symmetry, even if we add the original Kulish-Faddeev dressing operators. We then propose new dressed states which are consistent with …

Near Conformal Perturbation Theory In Syk Type Models, Sumit R. Das, Animik Ghosh, Antal Jevicki, Kenta Suzuki

Physics and Astronomy Faculty Publications

We present a systematic procedure to extract the dynamics of the low energy soft mode in SYK type models with a single energy scale J and emergent reparametrization symmetry in the IR. This is given in the framework of the perturbative scheme of arXiv:1608.07567 based on a specific (off-shell) breaking of conformal invariance in the UV, adjusted to yield the exact large-N saddle point. While this breaking term formally vanishes on-shell, it has a non-trivial effect on correlation functions and the effective action. In particular, it leads to the Schwarzian action with a specific coupling to bi-local matter. The …

Evidence For Electron Energization Accompanying Spontaneous Formation Of Ion Acceleration Regions In Expanding Plasmas, Evan M. Aguirre, Rikard Bodin, Neng Yin, Timothy N. Good, Earl E. Scime

Physics and Astronomy Faculty Publications

We report experiments conducted in an expanding argon plasma generated in the inductive mode of a helicon source in the Hot hELIcon eXperiment–Large Experiment on Instabilities and Anisotropies facility. As the neutral gas pressure increases, the supersonic ion acceleration weakens. Increasing neutral pressure also alters the radial profile of electron temperature, density, and plasma potential upstream of the plasma expansion region. Langmuir probe measurements of the electron energy probability function (EEPF) show that heating of electrons at the plasma edge by RF fields diminishes with increasing gas pressure, yielding a plasma with a centrally peaked electron temperature, and flat potential …

Cft Unitarity And The Ads Cutkosky Rules, David Meltzer, Allic Sivaramakrishnan

Physics and Astronomy Faculty Publications

We derive the Cutkosky rules for conformal field theories (CFTs) at weak and strong coupling. These rules give a simple, diagrammatic method to compute the double-commutator that appears in the Lorentzian inversion formula. We first revisit weakly-coupled CFTs in flat space, where the cuts are performed on Feynman diagrams. We then generalize these rules to strongly-coupled holographic CFTs, where the cuts are performed on the Witten diagrams of the dual theory. In both cases, Cutkosky rules factorize loop diagrams into on-shell sub-diagrams and generalize the standard S-matrix cutting rules. These rules are naturally formulated and derived in Lorentzian momentum space, …

High-Temperature Optical Properties Of Indium Tin Oxide Thin-Films, Jiwoong Kim, Sujan Shrestha, Maryam Souri, John G. Connell, Sungkyun Park, Ambrose Seo

Physics and Astronomy Faculty Publications

Indium tin oxide (ITO) is one of the most widely used transparent conductors in optoelectronic device applications. We investigated the optical properties of ITO thin films at high temperatures up to 800 °C using spectroscopic ellipsometry. As temperature increases, amorphous ITO thin films undergo a phase transition at ~ 200 °C and develop polycrystalline phases with increased optical gap energies. The optical gap energies of both polycrystalline and epitaxial ITO thin films decrease with increasing temperature due to electron-phonon interactions. Depending on the background oxygen partial pressure, however, we observed that the optical gap energies exhibit reversible changes, implying that …

Testing A Thermodynamic Approach To Collective Animal Behavior In Laboratory Fish Schools, Julia A. Giannini, James G. Puckett

Physics and Astronomy Faculty Publications

Collective behaviors displayed by groups of social animals are observed frequently in nature. Understanding and predicting the behavior of complex biological systems is dependent on developing effective descriptions and models. While collective animal systems are characteristically nonequilibrium, we can employ concepts from equilibrium statistical mechanics to motivate the measurement of material-like properties in laboratory animal aggregates. Here, we present results from a new set of experiments that utilize high speed footage of two-dimensional schooling events, particle tracking, and projected static and dynamic light fields to observe and control the behavior of negatively phototaxic fish schools (Hemigrammus bleheri). First, …

Additive Modulation Of Dna-Dna Interactions By Interstitial Ions, Wei Meng, Raju Timsina, Abby Bull, Kurt Andresen, Xiangyun Qiu

Physics and Astronomy Faculty Publications

Quantitative understanding of biomolecular electrostatics, particularly involving multivalent ions and highly charged surfaces, remains lacking. Ion-modulated interactions between nucleic acids provide a model system in which electrostatics plays a dominant role. Using ordered DNA arrays neutralized by spherical cobalt3+ hexammine and Mg2+ ions, we investigate how the interstitial ions modulate DNA-DNA interactions. Using methods of ion counting, osmotic stress, and x-ray diffraction, we systematically determine thermodynamic quantities, including ion chemical potentials, ion partition, DNA osmotic pressure and force, and DNA-DNA spacing. Analyses of the multidimensional data provide quantitative insights into their interdependencies. The key finding of this study is that …

Time Dependence Of Few-Body Forster Interactions Among Ultracold Rydberg Atoms, Zhimin Cheryl Liu, Nina P. Inman, Thomas J. Carroll, Michael W. Noel

Physics and Astronomy Faculty Publications

Rubidium Rydberg atoms in either |m_j| sublevel of the 36p_3/2 state can exchange energy via Stark-tuned Förster resonances, including two-, three-, and four-body dipole-dipole interactions. Three-body interactions of this type were first reported and categorized by Faoro et al. [Nat. Commun. 6, 8173 (2015)] and their Borromean nature was confirmed by Tretyakov et al. [Phys. Rev. Lett. 119, 173402 (2017)]. We report the time dependence of the N-body Förster resonance N×36p_3/2,|mj|=1/2→36s_1/2+37s_1/2+(N−2)×36p_3/2,|mj|=3/2, for N=2, 3, …

Effect Of Thomas Rotation On The Lorentz Transformation Of Electromagnetic Fields, Lakshya Malhotra, Robert Golub, Eva Kraegeloh, Nima Nouri, Bradley R. Plaster

Physics and Astronomy Faculty Publications

A relativistic particle undergoing successive boosts which are non collinear will experience a rotation of its coordinate axes with respect to the boosted frame. This rotation of coordinate axes is caused by a relativistic phenomenon called Thomas Rotation. We assess the importance of Thomas rotation in the calculation of physical quantities like electromagnetic fields in the relativistic regime. We calculate the electromagnetic field tensor for general three dimensional successive boosts in the particle's rest frame as well as the laboratory frame. We then compare the electromagnetic field tensors obtained by a direct boost [Formula: see text] and successive boosts [Formula: …

Perturbed Field Ionization For Improved State Selectivity, Vincent C. Gregoric, Jason Bennett, Bianca R. Gualtieri, Hannah P. Hastings, Ankitha Kannad, Zhimin Cheryl Liu, Maia R. Rabinowitz, Zoe A. Rowley, Maio Wang, Lauren Yoast, Thomas J. Carroll, Michael W. Noel

Physics and Astronomy Faculty Publications

Selective field ionization (SFI) is used to determine the state or distribution of states to which a Rydberg atom is excited. By evolving a small perturbation to the ramped electric field using a genetic algorithm, the shape of the time-resolved ionization signal can be controlled. This allows for the separation of signals from pairs of states that would be indistinguishable with unperturbed SFI. Measurements and calculations are presented that demonstrate this technique and shed light on how the perturbation directs the pathway of the electron to ionization. Pseudocode for the genetic algorithm is provided. Using the improved resolution afforded by …

Similarities Between Insect Swarms And Isothermal Globular Clusters, Dan Gorbonos, Kasper Van Der Vaart, Michael Sinhuber, James G. Puckett, Andrew M. Reynolds, Nicholas T. Ouellette, Nir S. Gov

Physics and Astronomy Faculty Publications

Previous work has suggested that disordered swarms of flying insects can be well modeled as self-gravitating systems, as long as the “gravitational” interaction is adaptive. Motivated by this work, we compare the predictions of the classic, mean-field King model for isothermal globular clusters to observations of insect swarms. Detailed numerical simulations of regular and adaptive gravity allow us to expose the features of the swarms' density and velocity profiles that are due to long-range interactions and are captured by the King model phenomenology, and those that are due to adaptivity and short-range repulsion. Our results provide further support for adaptive …

Lorentz And Cpt Tests Using Penning Traps, Yunhua Ding

Physics and Astronomy Faculty Publications

The theoretical prospects for quantum electrodynamics with Lorentz-violating operators of mass dimensions up to six are revisited in this work. The dominant effects due to Lorentz and CPT violation are studied in measurements of magnetic moments of particles confined in Penning traps. Using recently reported experimental results, new coefficients for Lorentz violation are constrained and existing bounds of various coefficients are improved.

Hyperfine Splitting In Muonium: Accuracy Of The Theoretical Prediction, Michael I. Eides

Physics and Astronomy Faculty Publications

In the last twenty years, the theory of hyperfine splitting in muonium developed without any experimental input. Finally, this situation is changing and a new experiment on measuring hyperfine splitting in muonium is now in progress at J-PARC. The goal of the MuSEUM experiment is to improve by an order of magnitude experimental accuracy of the hyperfine splitting and muon-electron mass ratio. Uncertainty of the theoretical prediction for hyperfine splitting will be crucial for comparison between the forthcoming experimental data and the theory in search of a possible new physics. In the current literature estimates of the error bars of …

Dressed States From Gauge Invariance, Hayato Hirai, Sotaro Sugishita

Physics and Astronomy Faculty Publications

The dressed state formalism enables us to define the infrared finite S-matrix for QED. In the formalism, asymptotic charged states are dressed by clouds of photons. The dressed asymptotic states are originally obtained by solving the dynamics of the asymptotic Hamiltonian in the far past or future region. However, there was an argument that the obtained dressed states are not gauge invariant. We resolve the problem by imposing a correct gauge invariant condition. We show that the dressed states can be obtained just by requiring the gauge invariance of asymptotic states. In other words, Gauss’s law naturally leads to …

Dual Superconformal Symmetry Of N = 2 Chern-Simons Theory With Fundamental Matter At Large N, Karthik Inbasekar, Sachin Jain, Sucheta Majumdar, Pranjal Nayak, Turmoli Neogi, Ritam Sinha, Tarun Sharma, V. Umesh

Physics and Astronomy Faculty Publications

Dual conformal symmetry and Yangian symmetry are symmetries of amplitudes that have aided the study of scattering amplitudes in highly supersymmetric theories like N = 4 SYM and ABJM. However, in general such symmetries are absent from the theories with lesser or no supersymmetry. In this paper, we show that the tree level 2 → 2 scattering amplitude in the 3d N = 2 Chern-Simons theory coupled to a fundamental chiral multiplet is dual superconformal invariant. In the ’t Hooft large N limit, the 2 → 2 scattering amplitude in this theory has been shown to be tree-level exact in …

Charting The Space Of 3d Cfts With A Continuous Global Symmetry, Anatoly Dymarsky, Joao Penedones, Emilio Trevisani, Alessandro Vichi

Physics and Astronomy Faculty Publications

We study correlation functions of a conserved spin-1 current J_μ in three dimensional Conformal Field Theories (CFTs). We investigate the constraints imposed by permutation symmetry and current conservation on the form of three point functions ⟨J_μJ_νO_Δ,ℓ⟩ and the four point function ⟨J_μJ_νJ_ρJ_σ⟩ and identify the minimal set of independent crossing symmetry conditions. We obtain a recurrence relation for conformal blocks for generic spin-1 operators in three dimensions. In the process, we improve several technical points, facilitating the use of recurrence relations. By applying …

Exact Generalized Partition Function Of 2d Cfts At Large Central Charge, Anatoly Dymarsky, Kirill Pavlenko

Physics and Astronomy Faculty Publications

We discuss generalized partition function of 2d CFTs on thermal cylinder decorated by higher qKdV charges. We propose that in the large central charge limit qKdV charges factorize such that generalized partition function can be rewritten in terms of auxiliary non-interacting bosons. The explicit expression for the generalized free energy is readily available in terms of the boson spectrum, which can be deduced from the conventional thermal expectation values of qKdV charges. In other words, the picture of the auxiliary non-interacting bosons allows extending thermal one-point functions to the full non-perturbative generalized partition function. We verify this conjecture for the …