Seminars

Date	Presenter	Title	Abstract	Links
_{January 25th, 2024}	_{Assistant Professor Sergio de la Barrera, Department of Physics, University of Toronto}	_{Emergent symmetries and properties in graphene multilayers}	_{Graphene is a beautiful and incredibly versatile platform for investigating emergent electronic phenomena. Confining electrons to two dimensions enhances their influence on one another, and empowers us to alter their environment with external fields and additional layers. Strategic combinations and arrangements of layered materials can yield new physics and surprising electronic properties. This seminar presents how certain combinations lead to superconductivity, magnetism, and topology from materials that have none of these properties on their own, and how they can address essential questions in quantum materials research.}	_{Read more}
_{February 29th, 2024} February29th2024	_{Postdoctoral Fellow Bowen Yang, Institute for Quantum Computing, University of Waterloo}	_{Probing 2D and Moiré Magnetism through Tunneling Transport}	_{A series of results is presented on a two-dimensional (2D) magnetic material, CrI3, in the atomically thin limit and in a twisted structure, using electrical tunneling transport and/or spectroscopy. In the former, the research group discovers over one million percent of magnetoresistance and obtain a simple microscopic Hamiltonian describing the 2D spin system. In the latter, they find new hysteretic and anisotropic field evolution of the magnetization behavior, arising from coexistence of AFM and FM interlayer interactions. They further uncover two distinct non-volatile spin textures at around 1 degree twist angle with different tunneling resistance that can be switched by magnetic field.}	_{Video link} iewseminar
_{March 21st, 2024}	_{Assistant Professor Stephen M. Wu, Department of Electrical and Computer Engineering, University of Rochester}	_{Strain engineering 2D quantum materials}	_{Strain engineering in electronics has been widely utilized over the last 20 years to enhance carrier mobility in most standard Si-based CMOS fabrication processes. These process-induced strain engineering techniques, engineered from the nanofabrication process itself, are simple, reliable, applied device-to-device, and highly scalable down to the nanometer scale. In this talk, Prof. Stephen M. Wu introduces his group work in exploring how process-induced strain engineering translates to the world of 2D materials, and how this may be applied to engineer quantum materials properties. Control over the strain degree-of-freedom in 2D materials opens new pathways for exploration in engineered quantum materials, since strain in weakly-bonded 2D systems can go far beyond strain-engineering in conventional 3D-bonded materials. This is discussed in the context of two different ongoing projects in Prof. Wu group: 2D straintronic phase-change transistors/memristors, and moiré superlattice engineering with strain in twisted and untwisted bilayer 2D heterostructures.}	_{Read more} _{Video link}
_{May 13th, 2024}	_{PhD Student Alina Wania Rodrigues, Quantum Theory Group, University of Ottawa}	_{Designing programmable simulators of strongly correlated electron systems in 2D materials}	_{In this work, we present a Hofstadter’s butterfly spectrum for the magic angle twisted bilayer graphene (MATBG) obtained using an abinitio based multi-million atom tight-binding model. We incorporate a hexagonal boron nitride substrate and out-of-plane atomic relaxation. The effects of a magnetic field are introduced via the Peierls modification of the long-range tight-binding matrix elements and the Zeeman spin splitting effects. A nanoribbon geometry is studied, and the quantum size effects for the sample widths up to 1μ are analyzed both for a large energy window and for the flatband around the Fermi level. For sufficiently wide ribbons, where the role of the finite geometry is minimized, we obtain and plot the Hofstadter spectrum and identify the in-gap Chern numbers by counting the total number of chiral edge states crossing these gaps. Subsequently, we examine the Wannier diagrams to identify the insulating states at charge neutrality.}	_{Read more} _{Video link}

_{January 25th, 2024}

_{Assistant Professor Sergio de la Barrera, Department of Physics, University of Toronto}

_{Emergent symmetries and properties in graphene multilayers}

_{Graphene is a beautiful and incredibly versatile platform for investigating emergent electronic phenomena. Confining electrons to two dimensions enhances their influence on one another, and empowers us to alter their environment with external fields and additional layers. Strategic combinations and arrangements of layered materials can yield new physics and surprising electronic properties. This seminar presents how certain combinations lead to superconductivity, magnetism, and topology from materials that have none of these properties on their own, and how they can address essential questions in quantum materials research.}

_{Read more}

_{February 29th, 2024}
February29th2024

_{Postdoctoral Fellow Bowen Yang, Institute for Quantum Computing, University of Waterloo}

_{Probing 2D and Moiré Magnetism through Tunneling Transport}

_{A series of results is presented on a two-dimensional (2D) magnetic material, CrI3, in the atomically thin limit and in a twisted structure, using electrical tunneling transport and/or spectroscopy. In the former, the research group discovers over one million percent of magnetoresistance and obtain a simple microscopic Hamiltonian describing the 2D spin system. In the latter, they find new hysteretic and anisotropic field evolution of the magnetization behavior, arising from coexistence of AFM and FM interlayer interactions. They further uncover two distinct non-volatile spin textures at around 1 degree twist angle with different tunneling resistance that can be switched by magnetic field.}

_{Video link} iewseminar

_{March 21st, 2024}

_{Assistant Professor Stephen M. Wu, Department of Electrical and Computer Engineering, University of Rochester}

_{Strain engineering 2D quantum materials}

_{Strain engineering in electronics has been widely utilized over the last 20 years to enhance carrier mobility in most standard Si-based CMOS fabrication processes. These process-induced strain engineering techniques, engineered from the nanofabrication process itself, are simple, reliable, applied device-to-device, and highly scalable down to the nanometer scale. In this talk, Prof. Stephen M. Wu introduces his group work in exploring how process-induced strain engineering translates to the world of 2D materials, and how this may be applied to engineer quantum materials properties. Control over the strain degree-of-freedom in 2D materials opens new pathways for exploration in engineered quantum materials, since strain in weakly-bonded 2D systems can go far beyond strain-engineering in conventional 3D-bonded materials. This is discussed in the context of two different ongoing projects in Prof. Wu group: 2D straintronic phase-change transistors/memristors, and moiré superlattice engineering with strain in twisted and untwisted bilayer 2D heterostructures.}

_{Read more}
_{Video link}

_{May 13th, 2024}

_{PhD Student Alina Wania Rodrigues, Quantum Theory Group, University of Ottawa}

_{Designing programmable simulators of strongly correlated electron systems in 2D materials}

_{In this work, we present a Hofstadter’s butterfly spectrum for the magic angle twisted bilayer graphene (MATBG) obtained using an abinitio based multi-million atom tight-binding model. We incorporate a hexagonal boron nitride substrate and out-of-plane atomic relaxation. The effects of a magnetic field are introduced via the Peierls modification of the long-range tight-binding matrix elements and the Zeeman spin splitting effects. A nanoribbon geometry is studied, and the quantum size effects for the sample widths up to 1μ are analyzed both for a large energy window and for the flatband around the Fermi level. For sufficiently wide ribbons, where the role of the finite geometry is minimized, we obtain and plot the Hofstadter spectrum and identify the in-gap Chern numbers by counting the total number of chiral edge states crossing these gaps. Subsequently, we examine the Wannier diagrams to identify the insulating states at charge neutrality.}

_{Read more}
_{Video link}

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