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UF PHYSICS COLLOQUIUM SCHEDULE

SPRING 2024

Colloquia begin at 3:00pm on Thursdays and are held in NPB 1002 unless otherwise noted.
Some colloquia will also be available through Zoom (link).


Contact: Imre Bartos (imrebartos@ufl.edu)


Department of Physics Colloquium Committee: 

Imre Bartos (chair), Jeff Andrews, Rachel Houtz, Sergey Klimenko, Andrey Korytov,, 

Dominique Laroche, Konstantin Matchev, Tarek Saab, Yuta Takahashi



January 11 (Thursday)

 

Speaker

Zoe Zhu

 

Location

NPB 1002

 

Title

Multiscale models for moiré materials

 

Abstract

Manipulating the twist angle or lattice mismatch in stacks of multilayered two-dimensional (2D) materials, referred to as van der Waals (vdW) heterostructures, introduces a long-wavelength moiré potential that fundamentally alters the physical properties of the constituent materials. Following the initial discovery of superconductivity in single-twist moiré systems, forays into moiré of moiré vdW heterostructures, such as twisted trilayer graphene with two independent twist angles, have led to observations of novel correlated states. These complex multilayered heterostructures exhibit length scales that are generally orders of magnitude longer than the bilayer moiré length, and they are incommensurate even in the continuum limit. To overcome these computational challenges, we present an efficient and accurate multiscale framework based on first principles. Using this framework, we study the electronic structures, mechanical relaxation, and phonon properties of complex vdW heterostructures and help interpret experimental observations.

 

Host

Xiaoguang Zhang


January 18 (Thursday)

 

Speaker

Guang Yue (University of Illinois Urbana-Champaign)

 

Location

NPB 2205

 

Title

A Study on Quantum Devices and Quantum Materials

 

Abstract

The Josephson junction device is a powerful tool to study physics. In this presentation the weak link Josephson junction and the topological insulator-based Josephson junction devices will be discussed. First, a superconducting quantum interference device made of weak link Josephson junctions can work directly in a high magnetic field which provides high sensitivity and spacial resolution on magnetic sample measurement. Such a device has been built into a spin resonance measurement setup to study quantum spin for quantum computing purposes. Second, the Majorana bound state physics are studied on the topological insulator-based Josephson junction devices. Evidence of the Majorana bound state is discussed together with methods to utilize such state for topological quantum computing.

 

Host

Mark Meisel


January 23 (Tuesday) (starting at 4pm!)

 

Speaker

Jiabin Yu (Princeton)

 

Location

NPB 2205

 

Title

Band geometry and topology in correlated quantum materials

 

Abstract

Band geometry (or quantum geometry) and band topology describe, respectively, the local and global properties of Bloch electron wavefunctions in quantum materials. These concepts have already triggered a revolution in quantum materials based on single-particle physics, but their significance in interacting systems is much less explored. In this talk, I will discuss two recent advances in this direction for the two major interactions in solids: electron-phonon interaction and electron-electron Coulomb interaction. First, I will explain how quantum geometry contributes crucially to the electron-phonon interaction, potentially offering a new design principle for higher-temperature superconductors. Second, we show that band geometry/topology and band mixing are key to explaining various experimental puzzles centered around fractional Chern insulators (FCIs) recently observed in twisted MoTe2 and graphene-hBN superlattices. FCIs, the zero-field analogs of the fractional quantum Hall effect, are induced by the Coulomb interaction in fractionally filled, (nearly-)flat topological bands, and their discovery heralds the discovery of more exotic topologically ordered phases. These phases, and the diverse computational tools required to predict them, will be discussed.

 

Host

Yuxuan Wang


January 25 (Thursday 1pm!)

 

Speaker

Kuate Defo (Princeton)

 

Location

NPB 2205

 

Title

Investigating Color Centers in Wide-Bandgap Semiconductors Through First-Principles DFT

 

Abstract

Density-Functional Theory (DFT) has seen tremendous improvements in the accuracy of its implementations since its first inception. The theory is characterized by the Nobel Prize-winning insight that the number density of electrons uniquely determines the ground-state properties of a system of atoms without the need to evaluate the many-body wavefunction for the electrons. In this talk, I will discuss another key insight that when coupled to DFT leads to exceptionally accurate predictions from first principles. The insight is that the Fermi level (the electronic chemical potential) is in some cases a manifestly local quantity rather than being uniform throughout a crystal sample as has been widely assumed in materials computations. This insight was used to accurately predict the measured values of electric fields probed using color centers in diamond to improve the functioning of semiconductor devices, leading to the selection of the work as an Editors’ Suggestion in Phys. Rev. B. The insight was also used to accurately determine timescales for charge-state decay of ionized color centers in diamond with applications in computation, communication, and sensing. In addition to the many opportunities offered by the treatment of the Fermi level as a local quantity in materials theory and computation, I will discuss the ability of DFT to characterize properties and phenomena such as the hyperfine interaction for group-IV impurity-vacancy color centers in diamond.

 

Host

Xiaoguang Zhang


January 25 (Thursday)

 

Speaker

Hitoshi Murayama (Berkeley)

 

Location

NPB 1002

 

Title

US Particle Physics for the Next Ten Years

 

Abstract

The US particle physics community has gone through a long-range planning exercise for the next ten years. The Particle Physics Project Prioritization Panel (P5) issued a report with recommendations to Department of Energy and National Science Foundation. I discuss how the report defines its scientific scope, what the major initiatives are in the next ten years, derived from a long-term vision for the field. The report also recommends creating a balanced portfolio in the program for all sizes and time scales, domestic vs international, and different subfields.

 

Host

Andrey Korytov


January 31 (Wednesday)

 

Speaker

Yinong Zhou (UC Irvine)

 

Location

NPB 2205

 

Title

Quantum Phases in Topological and Chiral Materials

 

Abstract

Topological and chiral quantum materials exhibit intriguing electronic, magnetic, and optical properties, holding great promise to shape future electronic and spintronic technologies. In this talk, I will show three different approaches to manipulate quantum phases, based on physics models and density functional theory (DFT) calculations. First, exotic electronic band structures are realized through atomic lattice design, as exemplified by the design of perfectly flat bands based on the line graph theorem. The completely quenched electronic kinetic energy in a flat band magnifies any finite electron-electron interaction, leading to a range of exotic quantum phases, such as ferromagnetism, superconductivity, and Mott insulating state. Specifically, I will present a system with two flat bands of opposite chirality that induces a giant circular dichroism effect and transitions from a flat-band material to a Mott insulator through orbital design. Secondly, topological states are manipulated by applying an external field, which can be either an electric, magnetic, or strain field. As an example, I will demonstrate a physical mechanism to remotely control the topological corner states in a higher-order topological insulator. Thirdly, structural chirality engenders a chiral-induced spin selectivity effect, which enables the harnessing of electron spin to open promising opportunities in spintronics and quantum technologies. Especially, I will showcase the realization of higher-dimensional spin selectivity in chiral crystals for controlling phase transition and spin-flipping processes.

 

Host

Xiaoguang Zhang


February 1 (Thursday)

 

Speaker

Sumitabha Brahmachari, Center for Theoretical Biological Physics, Rice University

 

Location

NPB 1002

 

Title

Physical modeling of chromosomes across species: mec anistic insights and biological consequences of emergent structural features

 

Abstract

Chromosomes are long polymers of DNA that are folded into a tiny nucleus by a concerted activity of various proteins. Quantitative understanding of the mechanistic link between protein activity, chromosome architecture, and biological function is nascent but imperative to comprehend how the DNA code governs cellular life. Establishing these links will steer biological research and yield fruitful discoveries in the physics of active polymers. In this talk, I will focus on a physical simulation framework that incorporates genomic data and furnishes mechanistic insights into regulating chromosome structure. I will discuss how this framework has been crucial in rationalizing our observations, linking the activity of specific proteins to conserved architectural features of chromosomes across species spanning the tree of life. We find that the species-wide diversity of structures emerges from a competition between three kinds of generalized forces, where the balance between these forces depends on the relative abundance of specific proteins and is a predictor of the structure. Using this framework, we further explore the elusive link between chromosome structure and crucial biological functionality like segregation or replicated DNA. The developed framework is an essential stride towards a cohesive, physics-based understanding of the chromosome architecture and its implications for cellular life.

 

Host

BingKan Xue


February 7 (Wednesday!)

 

Speaker

Arkajit Mandal (Columbia University)

 

Location

NPB 2205

 

Title

Quantum Dynamics of Light and Matter between Two Mirrors

 

Abstract

Placing molecules and materials between mirrors (or inside optical cavities) can enable the generation of exciting new chemical and physical phenomena in a highly controllable manner. In this talk, I will share a few of our theoretical works that demonstrate how photons can play the roles of a catalyst, a solvent, a quantum degree of freedom, beyond their usual role as a source of energy, to modify the chemical and physical properties of molecules and materials that are coupled to quantized radiation. First, I will discuss how quantum light-matter interactions can be utilized to modify the photochemistry of molecules and how a single photon can act as a catalyst to initiate multiple chemical reactions, leading to a quantum yield of more than one. Second, I will share our theoretical work that investigates how coupling molecular vibrations to vacuum radiation inside optical cavities can suppress or enhance the cleavage of specific chemical bonds, as seen in several recent experiments. I will share our theories that reveal that photons can act like solvents to enhance or suppress ground-state chemical kinetics. Next, I will show that quantum light-matter interactions can modify exciton-phonon interactions and can lead to the suppression of phonon-mediated decoherence. This enables fast ballistic transport in materials that are coupled to cavity radiation. I will share experimental results from our collaborators that confirm our theoretical predictions. Finally, I will share our theoretical framework, the quasi-diabatic propagation scheme, that allows for performing on-the-fly ab-initio quantum dynamics simulations, enabling us to investigate a wide range of problems, from photochemistry to polariton chemistry and beyond.

 

Host

Amlan Biswas


February 8 (Thursday)

 

Speaker

Gabriel Birzu (Stanford University)

 

Location

NPB 1002

 

Title

Do bacteria form species? Long term evolution leads to frequent hybridization in a natural microbial community

 

Abstract

Genetic sequencing of natural bacterial populations often reveals distinct genomic clusters, which are usually interpreted as distinct species. At the same time, recent studies have shown extensive recombination across a wide range of genetic divergences, raising the question of how clusters can be maintained over time. Previous studies have shown that ecological separation can emerge within highly-recombining bacterial populations. However, whether this mechanism can prevent the hybridization and merging of distinct clusters is not known. Here, I show that thermophilic cyanobacteria from the Yellowstone National Park form a rare natural experiment to address this question. By analyzed a large collection of single-cell genomes, I demonstrate that despite their different ecologies, continual hybridization and natural selection have gradually eroded the genetic differences between clusters. These results suggest that ecological barriers cannot by themselves maintain genomic clusters over long evolutionary times and highlight the importance of spatial dynamics for maintaining microbial diversity.

 

Host

BingKan Xue


February 15 (Thursday)

 

Speaker

RESERVED

 

Location

NPB 1002

 

Title


 

Abstract


 

Host



February 22 (Thursday)

 

Speaker

Junxin Chen (MIT)

 

Location

NPB 1002

 

Title

Preparing Macroscopic Quantum Mechanical Oscillators by Measurement

 

Abstract

Macroscopic mechanical oscillators prepared in quantum states are valuable resources to explore the boundary between the typically microscopic quantum world and the typically macroscopic classical world. This topic points to new physics beyond the current framework of quantum mechanics. Measurement in the quantum regime not only allows acquiring information of a physical observable at an unprecedented level, but also shapes the state of the system under measurement. In this talk, I will introduce my works demonstrating measurement-based preparation of macroscopic mechanical oscillators into their quantum ground states, and the ongoing work of preparing a macroscopic system into a quantum squeezed state. These works pave the way to studying macroscopic quantum systems.

 

Host

Paul Fulda


February 29 (Thursday)

 

Speaker

RESERVED

 

Location

NPB 1002

 

Title


 

Abstract


 

Host



March 7 (Thursday)

 

Speaker

Chang Long

 

Location

NPB 1002

 

Title


 

Abstract


 

Host

Physics Graduate Community


March 21 (Thursday)

 

Speaker

Lam Hui (Columbia)

 

Location

NPB 1002

 

Title


 

Abstract


 

Host

Wei Xue


March 28 (Thursday)

 

Speaker

Paul Steinhardt (Princeton)

 

Location

NPB 1002

 

Title


 

Abstract


 

Host

BingKan Xue


April 4 (Thursday)

 

Speaker

Joe LaVeigne

 

Location

NPB 1002

 

Title


 

Abstract


 

Host

Physics Graduate Community


April 11 (Thursday)

 

Speaker

Patrick Brady (UW Milwaukee)

 

Location

NPB 1002

 

Title


 

Abstract


 

Host

Imre Bartos







FALL 2024




September 19 (Thursday)

 

Speaker

Steve Taylor (Vanderbilt)

 

Location

NPB 1002

 

Title


 

Abstract


 

Host

Jeff Dror


September 26 (Thursday)

 

Speaker


 

Location

NPB 1002

 

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Abstract


 

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October 10 (Thursday)

 

Speaker


 

Location

NPB 1002

 

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Abstract


 

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October 24 (Thursday)

 

Speaker


 

Location

NPB 1002

 

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October 31 (Thursday)

 

Speaker


 

Location

NPB 1002

 

Title


 

Abstract


 

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November 7 (Thursday)

 

Speaker


 

Location

NPB 1002

 

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November 28 (Thursday)

 

Speaker


 

Location

NPB 1002

 

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December 5 (Thursday)

 

Speaker


 

Location

NPB 1002

 

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December 12 (Thursday)

 

Speaker


 

Location

NPB 1002

 

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