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CQRT Seminars

The Atomic, Molecular and Optical (AMO) and Condensed Matter (CM) physics groups are hosting a joint seminar as part of the Center for Quantum Research and Technology (CQRT).  This endowed seminar series brings in experts from across the country as well as across campus to discuss the latest in research advances in quantum science.

Seminars are scheduled for  2:30-3:30 pm on Tuesdays and/or Fridays, and are held either  in-person in Lin Hall 105 or on Zoom, depending upon speaker availability and preference.  Please check this web page or the email announcements for the current week's talks.

To get on the seminar mailing list, please contact one of the seminar orgainzers, Profs. Robert Lewis-Swan and Kieran Mullen

 

Fall 2022

Title:  New Materials Discovery by Molecular-beam Epitaxy 

Hanjong Paik, OU  

Tuesday, August 23,  2022
2:30-3:30pm (105 Lin Hall/Zoom Link will be announced).

Abstract:   The synthesis of complex oxide thin films by the molecular-beam epitaxy (MBE) technique provides a great potential for unleashing novel and hidden properties of the material from the dull ground states. Especially, when it utilizes the lattice coherency from the substrates, i.e., strain, the properties of thin films can be dramatically altered in comparison to their bulk form. Occasionally, this approach results in metastable phase and pseudomorphic polymorphism, thus, introducing the unexpected emergent properties owing to the power of epitaxial-strain-symmetry-stabilization at the interface. Therefore, the thin-film approach for new quantum material discovery will be the ultimate platform for the fundamental study of new quantum phenomena at the surface and interface. 

  In this talk, I would like to present how ozone-assist oxide MBE can be useful to discover new material properties, especially, relevant to the strongly correlated electronic system. I will talk about (1) room temperature high-electron-mobility and its 2DEG behavior of the perovskite stannate interface for the transparent power electronics (2) how simple metal ruthenium dioxide becomes a superconductor via. strain-stabilization, and (3) realization of epitaxial topological crystalline insulator Sr3SnO anti-perovskite system with in-situ spectroscopy. In addition to describing the above material synthesis and characterization, I also would like to discuss several challenging materials systems, for example, some cubic-to-hexagonal perovskite polymorphic systems, noble pyrochlore oxides system, and materials growth challenges containing alkaline metal elements (i.e., Li-, K-, Na- containing material system) for the fundamental study of quantum materials. 

Title:    Developing Quantum Information Devices and Systems using New Materials, Experiments, Nanostructures and Data-driven Models

Safura Sharifi, OU Dept. of Electrical and Computer Engineering

Tuesday, September 6, 2022
2:30-3:30pm (105 Lin Hall).

Abstract:   Quantum devices and systems are the heart of revolutionary technologies that open up new ways to collect and process information, perfectly secure communications, optimize computation problems, accurately measure physical phenomena, and many more. My research includes the applications of new materials, experiments, nanostructures, and data-driven models to impact the field of quantum science and technology. My presentation will explain integrating computational and experimental techniques to introduce new development, design, and implementation tools for quantum devices and quantum optical systems with more diverse and enhanced functionalities. My research presentation will discuss combining the knowledge of designing the optical structures and the dominant performance of rare-earth material to generate, manipulate, and store quantum light as well as control and use coherent atom-atom interactions for quantum information processing. In addition, I will discuss how to engineer the functionality of multilayer nanostructures to control optical properties for various applications ranging from spacecraft thermal control systems to advanced gravitational wave detectors that can minimize thermal noise below the standard quantum limit. Furthermore, I will provide my perspective on developing predictive performance models using computational and machine learning techniques to combat noise in optical and quantum optical systems and predict the performance of future experiments.

Title:  Colloidal Assembly at Fluid Interfaces

Sepideh Razavi, OU Dept. of Chemical, Biological and Medical Engineering.

Friday, September 16, 2021
2:30-3:30pm,  105 Lin Hall

Abstract:  The ubiquity of self-assembly - the process of creating organizational order in systems of components - in nature has inspired technological developments towards synthetic building blocks that assemble into desirable structures with a unique set of properties. Isotropic spherical colloids are a simple example of such building blocks where their spatial arrangement yields photonic crystals that exhibit structural color. The key step towards engineering the assembly process is the ability to tune the interparticle interactions. There is a concerted effort in the field to identify the factors that impact the interparticle interactions and control the assembly process. How is the assembly in bulk different from the 2D assembly in the presence of a fluid interface? What happens when shape or surface anisotropic (i.e., Janus) particles are used as building blocks for assembly? In this talk, I will present experiments on the application of fluid interfaces as a template for assembly; specifically, I will discuss the role of particle surface properties in tuning the mechanical stability and flow behavior of the assembled monolayer, important for applications in which the interface undergoes large deformations producing compression and shear stresses at the interface.

Title:  Molecular transistors as substitutes for quantum information applications

Mario Borunda, Oklahoma State University

Friday, September 23, 2022
2:30-3:30pm,  105 Lin Hall

Abstract:  Applications of quantum information generally rely on the generation and manipulation of qubits. Still, there are ways to envision a device with a continuous readout but without the entangled states. In this talk, I will discuss an alternative to the qubit, namely the solid-state version of the Mach–Zehnder interferometer, in which the local moments and spin polarization replace light polarization. Transistors based on such systems lead to the possibility of fabricating logic gates that do not require entangled states.

Title:    Strong coupling theory of twisted multilayer graphene systems: correlatedinsulators, collective excitations and superconductivity   

Eslam Khalaf, Harvard University

Tuesday, October 4th, 2022

2:30-3:30pm (105 Lin Hall/Zoom Link will be announced).

Abstract:    I will discuss a recently developed strong coupling theory of magic-angle twisted bilayer graphene. I will begin by showing how the electronic structure of twisted bilayer graphene makes it possible to relate its flat bands to the lowest Landau levels. This leads to a model of twisted bilayer graphene consisting of two sets of U(4) symmetric Landau-level-like Chern bands with opposite Chern numbers that are tunnel-coupled. I will show how this model broadly captures most of the observed features of twisted bilayer graphene: correlated trivial and topological Chern insulators at integer fillings, fractional Chern insulators and superconductivity. The correlated insulators are understood as generalized quantum Hall ferromagnets. I will then discuss the nature of charged excitations on top of such correlated insulators showing that they admit non-trivial charged excitations in addition to single-particle excitations. These excitations are intimately tied to band topology and can take the form of skyrmions -- real space spin textues -- or spin polarons -- bound states of an electron and a spin waves. I will show that there is a very natural mechanism for superconductivity which leads to pairing of these charged excitations. This mechanism is purely repulsive in origin and relies on band topology in a fundamental way. At the end, I will discuss how these insights generalize to a class of multilayer graphene systems with alternating twist angle and contrast the properties of these systems compared to their bilayer counterpart.

Title:    TBA

Alexander Efros, Naval Research Lab

Tuesday, October 18th, 2022
2:00-3:00pm (105 Lin Hall/Zoom Link will be announced).

Abstract:   

Title:    TBA

Sarang Gopalakrishnan, Princeton University

Tuesday, October 24th, 2022
2:30-3:30pm (105 Lin Hall/Zoom Link will be announced).

Abstract:   

Title:  TBA

 Vito Scarola, Virginia Tech.

Friday, November 4th, 2022
2:30-3:30pm,  105 Lin Hall

Abstract:  

Title:    TBA

Nan Yu, NASA Jet Propulsion Laboratory

Tuesday, November 8th, 2022
2:30-3:30pm (105 Lin Hall/Zoom Link will be announced).

Abstract:   

Title:    TBA

Kevin Peak, Louisiana State University

Tuesday, December 6th, 2022
2:30-3:30pm (105 Lin Hall/Zoom Link will be announced).

Abstract:   

Spring 2022 (virtual Zoom series)

Title: Site-specific spectroscopic measurement of spin and charge in (LuFeO3)m/(LuFe2O4)1  multiferroic superlattices

Janice Musfeldt, University of Tennessee  

Tuesday, February 22, 2022
1:15-2:15pm (Zoom link will be announced)

Abstract:  Interface materials offer a means to achieve electrical control of ferrimagnetism at room temperature as was recently demonstrated in (LuFeO3)m/(LuFe2O4)1 superlattices. A challenge to understanding the inner workings of these complex magnetoelectric multiferroics is the multitude of distinct Fe centres and their associated environments. This is because macroscopic techniques characterize average responses rather than the role of individual iron centres. Here, we combine optical absorption, magnetic circular dichroism and first-principles calculations to uncover the origin of high-temperature magnetism in these superlattices and the charge-ordering pattern in the m = 3 member. In particular, interface spectra establish how Lu-layer distortion selectively enhances the Fe2+ → Fe3+ charge-transfer contribution in the spin-up channel, strengthens the exchange interactions and increases the Curie temperature. Comparison of predicted and measured spectra also identifies a non-polar charge ordering arrangement in the LuFe2O4 layer. This site-specific spectroscopic approach opens the door to understanding engineered materials with multiple metal centres and strong entanglement.

Title: Searches for New Physics with Quantum Sensors in the Laboratory and in Space

Marianna Safranova, University of Delaware

Tuesday, March 1, 2022
1:15-2:15pm (Zoom link will be announced)

Abstract:  The extraordinary advances in quantum control of matter and light have been transformative for atomic and molecular precision measurements enabling probes of the most basic laws of Nature to gain a fundamental understanding of the physical Universe. Exceptional versatility, inventiveness, and rapid development of precision experiments supported by continuous technological advances and improved atomic and molecular theory led to rapid development of many avenues to explore new physics. I will give an overview of atomic and molecular physics searches for physics beyond the standard model and focus of dark matter searches with atomic and nuclear clocks. Recent ideas on dark matter searches and test of general relativity with clocks in space will be discussed.  I will also briefly discuss new ideas and prototype experiments in gravitational wave detection with atomic quantum sensors.

Title: Bridging Few- And Many-Body Physics in Fermi Gases

Yangqian Yan, The Chinese University of Hong Kong

Friday, March 4, 2022
2:30-3:30pm (Zoom link will be announced)

Abstract:  The strongly interacting Fermi gas with large scattering lengths constitutes a paradigmatic model system that is relevant to atomic, condensed matter, nuclear and particle physics. Such a model applies to the core of nuclei, the crust of a neutron star, and the highly controllable ultracold atoms with tunable scattering lengths. Whereas it is challenging to theoretically tackle strongly interacting Fermi gases, the virial expansion serves as a powerful tool to bridge few- and many-body physics. With the help of Richard Feynman’s path integral, we used classical computers to simulate few-body systems and obtained the viral coefficients for many-body systems. In particular, I will discuss how to extract the so-called contact, the central quantity controlling dilute quantum systems, using the virial expansion. 

Including multiple flavors in interacting Fermi gases provides physicists with an even richer playground. In a recent collaboration with Prof. Gyu-Boong Jo’s group at HKUST, we have theoretically predicted and experimentally verified that the contact of a 3D SU(N) Fermi gas approaches spinless bosons via a particular scaling law at finite temperatures. This provides a rigorous proof of the bosonization of 3D SU(N) fermions and also opens the door to a new framework of manipulating quantum statistics in many-body systems.

Title: A Direct View into Optical Lattices: Dynamics, Topology and Dissipation

Klaus Sengstock,  University of Hamburg

Friday, March 11, 2022
2:30-3:30pm (Zoom link will be announced)

Abstract:  Ultracold atoms in optical lattices act as powerful systems for quantum technologies, including quantum simulation, quantum information and quantum computing, as well as for precision experiments and as fully new model systems. I will report on recent developments from our lab to image 3D optical lattice systems with better than single-site resolution (Nature 599, 571 (2021)) allowing for a direct view into dynamics, thermalization and further properties within the optical lattices. We could observe the spontaneous build-up of a density waves (PRX, in print, arXiv:2108.11917) and study topological properties of quantum gases in lattices (Nature Physics, 15, 449 (2019)).

Title: Using Computational Methods to Improve and Design Energy Materials

MIchelle Johannes, Naval Research Lab

Tuesday, March 22, 2022
1:15-2:15pm (Zoom link will be announced)

Abstract:  Although batteries and fuel cells are generally considered electrochemical systems, a surprising amount of their performance stems from the physics of the materials that make up their basic components:anode, cathode and electrolyte.  Ionic conduction, electronic conductivity, chemical stability and voltage can all be traced back to intrinsic materials properties which are governed by fundamental physics.

In this talk, I will discuss how computational simulation can be used to analyze, develop and improve energy materials, such as  Li-ion batteries, supercapacitors, and fuel cells.  I will specifically discuss how seemingly small details of the electronic structure can make or break  performance.  I will further discuss some of the safety concerns that are currently driving battery research and development and how computational screening can determine in advance how stable a material will be during charging.  Finally, I will discuss the use of nanoscale materials and how they can be stabilized against degradation by judicious oxide coating.

Title:  Photons, plasmons, and polaritons: optical phenomena in quantum materials

Stephanie Law, University of Delaware

Tuesday, March 29, 2022
1:15-2:15pm (Zoom link will be announced)

 Abstract: When light interacts with quantum materials, we can excite a variety of modes including plasmon polaritons and optical phonons. In layered materials, these modes can interact with each other to produce hybrid excitations resulting in novel optical phenomena such as negative refraction, extreme light confinement, and preferential thermal emission. In this talk, I will first discuss our work on the growth of topological insulator thin films and heterostructures by molecular beam epitaxy. Topological insulators have two-dimensional surface states that house massless electrons, and the plasmon polaritons in these materials show unusual properties. I will discuss the dispersion of these modes and show record high mode indices and extremely long polariton lifetimes. Using MBE, we can then grow layered structures comprising multiple topological and normal insulators, resulting in hybrid coupled plasmon modes. We can also grow self-assembled topological insulator quantum dots, which could be used as qubits. I will close by discussing our work on semiconductor hyperbolic metamaterials, which are layered materials comprising alternating metallic and dielectric materials. I will show our work demonstrating strong coupling between the volume plasmon polariton modes and quantum well intersubband transitions.

Title: Emergence and quantum complexity in mono element solids

G. Baskaran, Matscience, IITMadras, Chennai, India

Friday, April 29, 2022
2:30-3:30pm (Zoom link will be announced)

Abstract:  We are witnessing gradual understanding of myriads of materials, synthetic quantum matter and ever growing number of phenomena and surprises. Emergence and quantum complexity are smiling at us. I will point to some of our works and briefly discuss two families: allotropes of carbon and solid hydrogen. Emergence creates a web of unexpected connections and new insights. For example, graphene offers [1,2] relativistic analogue of time dilation, Kaluza Klein collapse, zitterbewegung, parity anomaly, emergent gauge fields, Majorana Fermions etc. Small twists in bilayer graphene produces superconductor or Mott insulator ! Solid hydrogen under pressure takes us through a series of unexpected structures and Mott insulating phases, before becoming a metal that Wigner and Huntington envisaged in 1935.

[1] G. Baskaran, Quantum Complexity in Graphene, Mod. Phys. Lett., B25, 605 (2011)
[2] G. Baskaran, Physics of Quanta and Fields in Graphene,
   in `Graphene: Synthesis, Properties and Phenomena,
   Editors: C.N.R. Rao and A.K. Sood (Wiley)

Title: Connecting the dots

Michael Scheibner, University of California, Merced

Friday, April 15, 2022
2:30-3:30pm (Zoom link will be announced)

Abstract:  How many straight lines connect two dots? The answer: That depends on the dots and their environment. By placing two quantum dots near each other we can probe fundamental quantum mechanical properties of the semiconductor system and its interactions. Equipped with that knowledge we can start to tailor the quantum states to develop novel quantum-enhanced applications. In doing so, we make use of an enhanced versatility and functionality that arises from the superposition of states of the two dots. For example, their discrete electronic states and optical transitions can be tuned in-situ over tens of meV. As a result, it is possible to control and realize coupling between varieties of excitations of the solid-state system, ranging from different spin states, phonons to the mechanical motion of the system. In this seminar I will review the unique properties of coupled quantum dots and discuss their advantages as tools in quantum technologies, such as quantum photonics and quantum sensing.  

Title: Representing many-body quantum states with neural networks

Martin Gärttner, University of Heidelberg

Friday, April 29, 2022
2:30-3:30pm (Zoom link will be announced)

Abstract:  I will discuss the idea of using neural networks a variational ansatz for the quantum many-body wave function. These neural network quantum states have recently been employed for variational ground state search, quantum dynamics, and quantum state tomography. I will report on two contribution of our group on using neural network representations of mixed quantum states for simulating the dynamics of open quantum systems and for quantum state tomography.

Title: TBA

Henri Lezec, NIST

Friday, April 29, 2022
2:30-3:30pm (Zoom link will be announced)

Abstract:  TBA

Title:  TBA

David Ebert, OU

Tuesday, March 29, 2022 

1:15-2:15pm (Zoom link will be announced)

 Abstract: TBA

Title: Representing many-body quantum states with neural networks

Martin Gärttner, University of Heidelberg

Friday, April 29, 2022
2:30-3:30pm (Zoom link will be announced)

Abstract:  I will discuss the idea of using neural networks a variational ansatz for the quantum many-body wave function. These neural network quantum states have recently been employed for variational ground state search, quantum dynamics, and quantum state tomography. I will report on two contribution of our group on using neural network representations of mixed quantum states for simulating the dynamics of open quantum systems and for quantum state tomography.

Title:Quantum fluctuations in nonlinear Schrödinger breathers

O. V. Marchukov, Institut für Angewandte Physik, Technical University of Darmstadt, Germany

Monday May 16, 2022
SPECIAL TIME:  9:00-10:00am   (Zoom link will be announced)

Abstract: Solitons are nonlinear waves that show up in many different fields of physics: From solitary water waves to Langmuir waves in plasmas, the formation of solitons attracts the interest of theoreticians and experimentalists alike. In this talk, we focus on the two-soliton breathers – nonlinear superposition of two bright solitons – in one-dimensional Bose gases that were recently obtained experimentally [2,4]. We present the linearization approach that allows one to evaluate quantum fluctuations of the parameters that define the solitonic solutions.

Furthermore, we demonstrate the uncertainty relations of the parameters for both the fundamental soliton and breather. We also discuss the dissociation of breather under both the influence of an external perturbation [1] and the quantum fluctuations of relative velocity. The former allows us to evaluate the breather dissociation time, i.e. the time it takes for the constituent solitons to be significantly separated. Without an external perturbation, the dissociation does not occur in the mean-field regime, thus making the dissociation time a potentially observable manifestation of quantum effects [3].

References

[1] O. V. Marchukov et al., Phys. Rev. A 99, 063623 (2019).

[2] A. Di Carli et al., Phys. Rev. Lett. 123, 123602 (2019).

[3] O. V. Marchukov et al., Phys. Rev. Lett. 125, 050405 (2020).

[4] D. Luo et al., Phys. Rev. Lett. 125, 183902 (2020).

Title: Probing Fundamental Physics with Precision Molecular Spectroscopy

 Samuel Meek,  Max Planck Institute for Multidisciplinary Sciences, Gaettingen

Monday May 23, 2022
SPECIAL TIME:  9:00-10:00am   (Zoom link will be announced)

Abstract: Precise measurements of molecular transition frequencies can provide a means to test fundamental physical questions, such as whether there are additional forces between the nuclei that are not predicted by the standard model or if the masses of elementary particles vary over time.  Such measurements can also help determine physical constants more precisely and provide data that can be used to better interpret astronomical spectra.  In my lab, we have developed an apparatus for determining vibrational and electronic transition frequencies of isolated small molecules with high precision.  The central component of this apparatus is a precision laser system containing narrow-linewidth reference and spectroscopy lasers linked to each other and to an atomic clock reference using an optical frequency comb.  So far, we have used this apparatus to investigate electronic transitions in OH, OD, and SH, as well as vibrational transitions in HD and D₂.  In all of these measurements, we have been able to determine the absolute transition frequencies with orders of magnitude higher precision than previously reported and, in some cases, detect systematic errors in earlier, less precise measurements.  In future measurements, trapping the molecules and applying quantum techniques can help to achieve narrower transition linewidths and improve the precision further.