Oksana Ostroverkhova

Professor of Physics

Oregon State University

Title: Photophysics of organic materials: from ancient pigments to high-performance organic semiconductors

Abstract: Organic (opto)electronic materials have been explored in a variety of applications in electronics and photonics. They offer several advantages over traditional silicon technology, including low-cost processing, fabrication of large-area flexible devices, and widely tunable properties through functionalization of the molecules. Over the past decade, remarkable progress in the material design has been made, which led to a considerable boost in performance of organic thin-film transistors, solar cells, and other applications that rely on photophysics and/or (photo)conductive properties of the material. Nevertheless, a number of fundamental questions pertaining to light-matter interactions and charge carrier photogeneration and transport in these materials remain. In this presentation, I will give examples of our efforts aiming to understand and tune exciton, polariton, and charge carrier dynamics in high-performance organic materials and to develop novel, sustainable organic materials.

Oksana Ostroverkhova

Professor of Physics

Oregon State University

Title: Photophysics of organic materials: from ancient pigments to high-performance organic semiconductors

Abstract: Organic (opto)electronic materials have been explored in a variety of applications in electronics and photonics. They offer several advantages over traditional silicon technology, including low-cost processing, fabrication of large-area flexible devices, and widely tunable properties through functionalization of the molecules. Over the past decade, remarkable progress in the material design has been made, which led to a considerable boost in performance of organic thin-film transistors, solar cells, and other applications that rely on photophysics and/or (photo)conductive properties of the material. Nevertheless, a number of fundamental questions pertaining to light-matter interactions and charge carrier photogeneration and transport in these materials remain. In this presentation, I will give examples of our efforts aiming to understand and tune exciton, polariton, and charge carrier dynamics in high-performance organic materials and to develop novel, sustainable organic materials.

Special Joint Semiar with Astronomy

Eugene Kolomeisky

Associate Professor of Physics

University of Virginia

Title: Coulomb Universe in a Jellium Droplet

Abstract: Analogy between the Coulomb law of interaction between charges and the Newton law of gravitational attraction between masses is familiar to every physics student.  In this talk I demonstrate that this analogy implies that a system of identical charges can evolve with time in a manner that parallels cosmological evolution of the physical Universe with hallmarks such as Hubble's law and Friedmann-type dynamics present.  The Coulomb and Newton laws are also dissimilar because the electrostatic force is many orders of magnitude larger than the gravitational force whose manifestations are only noticeable on astronomical scale.  On the other hand, analog cosmological evolutions driven by Coulomb interactions are predicted to be observable in laboratory experiments involving Coulomb explosions and electron density oscillations in conductors.

Special Joint Semiar with Astronomy

Eugene Kolomeisky

Associate Professor of Physics

University of Virginia

Title: Coulomb Universe in a Jellium Droplet

Abstract: Analogy between the Coulomb law of interaction between charges and the Newton law of gravitational attraction between masses is familiar to every physics student.  In this talk I demonstrate that this analogy implies that a system of identical charges can evolve with time in a manner that parallels cosmological evolution of the physical Universe with hallmarks such as Hubble's law and Friedmann-type dynamics present.  The Coulomb and Newton laws are also dissimilar because the electrostatic force is many orders of magnitude larger than the gravitational force whose manifestations are only noticeable on astronomical scale.  On the other hand, analog cosmological evolutions driven by Coulomb interactions are predicted to be observable in laboratory experiments involving Coulomb explosions and electron density oscillations in conductors.

Yafis Barlas

Assistant Professor of Physics

University of Nevada, Reno

Title: Correlated and Topological Phases in flat bands of two-dimensional crystals

Abstract: Due to their vanishing density of states and gapless semi-metallic behavior at charge neutrality, honeycomb lattice two-dimensional (2D) crystals are ideal candidates to host topological states. Even more interesting are twisted or strained 2D crystals, as the electron dispersion in these systems can be weakly dispersing, (i.e exhibit a small bandwidth) or completely flat. In these situations, the interplay of topology and correlation driven phases in flat bands of 2D crystals can result in emergent topological order.  Similarly, at high magnetic fields, multi-layer graphene and twisted bilayer graphene exhibit topological bands and various correlated states. In this talk, I will discuss a new class of interacting and non-interacting symmetry protected topological phases stabilized by mirror symmetry in 2D Dirac semi-metals. This quantum parity Hall state, exhibits two one-dimensional counter-propagating metallic edge states, distinguished by even or odd parity under the system’s mirror reflection symmetry.​ I will also discuss some of our results in twisted 2D crystals at high magnetic fields.

Yafis Barlas

Assistant Professor of Physics

University of Nevada, Reno

Title: Correlated and Topological Phases in flat bands of two-dimensional crystals

Abstract: Due to their vanishing density of states and gapless semi-metallic behavior at charge neutrality, honeycomb lattice two-dimensional (2D) crystals are ideal candidates to host topological states. Even more interesting are twisted or strained 2D crystals, as the electron dispersion in these systems can be weakly dispersing, (i.e exhibit a small bandwidth) or completely flat. In these situations, the interplay of topology and correlation driven phases in flat bands of 2D crystals can result in emergent topological order.  Similarly, at high magnetic fields, multi-layer graphene and twisted bilayer graphene exhibit topological bands and various correlated states. In this talk, I will discuss a new class of interacting and non-interacting symmetry protected topological phases stabilized by mirror symmetry in 2D Dirac semi-metals. This quantum parity Hall state, exhibits two one-dimensional counter-propagating metallic edge states, distinguished by even or odd parity under the system’s mirror reflection symmetry.​ I will also discuss some of our results in twisted 2D crystals at high magnetic fields.

Professor Mark Novotny

Mississippi State University

Department of Physics and Astronomy

Title: Generalization of Bloch’s Theorem for Tight-binding Models:Quantum Dragon Nanomaterials and Nanodevices

Abstract: Bloch’s Theorem arguably has the largest economic impact of any condensed matter theorem.  Bloch’s Theorem can only be used for translationally invariant systems, and together with the tight-binding model gives band structures and hence devices such as transistors and optoelectronics.  For tight-binding models, a generalization of Bloch’s Theorem for some strongly disordered (non-translationally invariant) systems is stated and proved.  The theorem generalization leads to predictions of novel electrical properties for some nanomaterials and nanodevices with strong disorder, whimsically called quantum dragons [1].  A number of different predictions of quantum dragon materials and devices [2] will be presented.  Furthermore, conjectures and testing of scaling for materials that are ‘close to quantum dragons’ are given [3].  For example, a perfect quantum wire is one in which impinging electrons from an appropriate incoming lead have probability unity of propagating through the device to the end of an outgoing lead, T(E)=1, for all electron energies E that propagate through the leads. Some quantum dragons are predicted to be perfect quantum wires (see the device in the figure below [3]), while others may make a unique FET (Field Effect Transistor) or quantum sensor or spintronics nanodevice. 

[1] M.A. Novotny, Energy-independent total quantum transmission of electrons through nanodevices with correlated disorder, Phys. Rev. B 90, 165103 (2014).

[2] G. Inkoom and M. Novotny, Quantum dragon solutions for electron transport through nanostructures based on rectangular graphs, J. Physics Commun. 11, 115019 (2018). 

[3] M.A. Novotny and T. Novotný, Order amidst Disorder in 2D+3D Quantum Dragon Composite Nanodevices with varying Breadth, J. Phys: Conf. Ser. 1740, 012002 (2021).

Professor Mark Novotny

Mississippi State University

Department of Physics and Astronomy

Title: Generalization of Bloch’s Theorem for Tight-binding Models:Quantum Dragon Nanomaterials and Nanodevices

Abstract: Bloch’s Theorem arguably has the largest economic impact of any condensed matter theorem.  Bloch’s Theorem can only be used for translationally invariant systems, and together with the tight-binding model gives band structures and hence devices such as transistors and optoelectronics.  For tight-binding models, a generalization of Bloch’s Theorem for some strongly disordered (non-translationally invariant) systems is stated and proved.  The theorem generalization leads to predictions of novel electrical properties for some nanomaterials and nanodevices with strong disorder, whimsically called quantum dragons [1].  A number of different predictions of quantum dragon materials and devices [2] will be presented.  Furthermore, conjectures and testing of scaling for materials that are ‘close to quantum dragons’ are given [3].  For example, a perfect quantum wire is one in which impinging electrons from an appropriate incoming lead have probability unity of propagating through the device to the end of an outgoing lead, T(E)=1, for all electron energies E that propagate through the leads. Some quantum dragons are predicted to be perfect quantum wires (see the device in the figure below [3]), while others may make a unique FET (Field Effect Transistor) or quantum sensor or spintronics nanodevice. 

[1] M.A. Novotny, Energy-independent total quantum transmission of electrons through nanodevices with correlated disorder, Phys. Rev. B 90, 165103 (2014).

[2] G. Inkoom and M. Novotny, Quantum dragon solutions for electron transport through nanostructures based on rectangular graphs, J. Physics Commun. 11, 115019 (2018). 

[3] M.A. Novotny and T. Novotný, Order amidst Disorder in 2D+3D Quantum Dragon Composite Nanodevices with varying Breadth, J. Phys: Conf. Ser. 1740, 012002 (2021).

Professor Hiro Nakamura

Department of Physics

University of Arkansas

Host: Seo

Title: Complex geometrical phases in quantum materials probed by transport

Abstract: Recent advances in condensed matter physics brought the phase part of wavefunction in the forefront, as exemplified by the Berry phase in graphene. However, experimentally probing complex phases in a momentum space is not easy. In this talk, we present how advanced transport techniques such as quantum interference and planer Hall effect could shed light on higher-order and/or anisotropic quantum phases in solids. We show recent application of these techniques to three-dimensional (3D) topological antiperovskites, which points to a unique spin/pseudospin texture in this material [1,2]. Preliminary results from a 2D material with distinct spin texture (few-layer WSe₂) also showcase an impact of different anisotropy of such phase patterns.

1. H. Nakamura et al., Nature Comm. 11, 1161 (2020).

2. D. Huang, H. Nakamura, and H. Takagi, arXiv:2101.05512 (2021)

Professor Hiro Nakamura

Department of Physics

University of Arkansas

Host: Seo

Title: Complex geometrical phases in quantum materials probed by transport

Abstract: Recent advances in condensed matter physics brought the phase part of wavefunction in the forefront, as exemplified by the Berry phase in graphene. However, experimentally probing complex phases in a momentum space is not easy. In this talk, we present how advanced transport techniques such as quantum interference and planer Hall effect could shed light on higher-order and/or anisotropic quantum phases in solids. We show recent application of these techniques to three-dimensional (3D) topological antiperovskites, which points to a unique spin/pseudospin texture in this material [1,2]. Preliminary results from a 2D material with distinct spin texture (few-layer WSe₂) also showcase an impact of different anisotropy of such phase patterns.

1. H. Nakamura et al., Nature Comm. 11, 1161 (2020).

2. D. Huang, H. Nakamura, and H. Takagi, arXiv:2101.05512 (2021)