Condensed Matter Seminar
Synthesis and characterization of tungsten oxide nanostructures for photocatalytic applications
Although in recent years researchers have committed significant efforts investigating properties and potential functionalities of metal oxides, commercially available oxide-based devices still
remain quite limited. Reasons for this include high material costs, sophisticated/non-scalable growth techniques, and insufficient enhancements over current industry standards. Our aim is
to narrow the divide that separates fundamental research and functional applications by developing efficient synthesis methods for strategic materials that will be highly impactful on
society. In particular we have identified tungsten oxide owing to its large abundance, optical bandgap, and versatile physical properties as an ideal candidate for photocatalytic hydrogen
production which has potential to provide a positive paradigm shift in society’s demand for fossil fuel generated energy, especially in developing portions of the world. Here I will discuss two
parallel approaches towards synthesizing tungsten oxide nanostructures that are cost effective, time efficient, and scalable along with their morphology, crystallinity, electronic properties, and
potential for utilization in functional devices.
Detection of 5/2 phases
Dr. Ankur Das
Postdoctoral Research Associate
Weizmann Institute of Science
Rehovot, Israel
Title: Detection of 5/2 phases
Abstract: The phases of the \nu=5/2 state have been shown to be very elusive but one of the most interesting ones as it is proposed to contain Majorana modes with non-abelian statistics. There is more than one candidate for the non-abelian state and among that three are the most promising ones namely pfaffian, anti-pfaffian, and particle-hole symmetric pfaffian. Quite a few experiments later the issue has not been settled. Previous efforts proposed methods to distinguish the candidates including the proposals where the order can be determined by measuring both thermal conductances and shot noise on the same device [Park et al. PRL 125, 157702 (2020)] or by only measuring the unequilibrated electrical conductance [Yutushui et al. PRL 128, 016401 (2022)]. To avoid some of the experimental challenges and limitations of the proposals including the above-mentioned ones we propose a new device made out of interfaces of the \nu=5/2 state and Abelian states. We propose to measure electrical shot noise to resolve among these states.
Detection of 5/2 phases
Dr. Ankur Das
Postdoctoral Research Associate
Weizmann Institute of Science
Rehovot, Israel
Title: Detection of 5/2 phases
Abstract: The phases of the \nu=5/2 state have been shown to be very elusive but one of the most interesting ones as it is proposed to contain Majorana modes with non-abelian statistics. There is more than one candidate for the non-abelian state and among that three are the most promising ones namely pfaffian, anti-pfaffian, and particle-hole symmetric pfaffian. Quite a few experiments later the issue has not been settled. Previous efforts proposed methods to distinguish the candidates including the proposals where the order can be determined by measuring both thermal conductances and shot noise on the same device [Park et al. PRL 125, 157702 (2020)] or by only measuring the unequilibrated electrical conductance [Yutushui et al. PRL 128, 016401 (2022)]. To avoid some of the experimental challenges and limitations of the proposals including the above-mentioned ones we propose a new device made out of interfaces of the \nu=5/2 state and Abelian states. We propose to measure electrical shot noise to resolve among these states.
Superfluid Helium Electromechanics
Professor John Davis
Associate Professor
University of Alberta
Department of Physics
Title: Superfluid Helium Electromechanics
Abstract: Liquid helium posses many properties that make it an attractive medium for studies of mechanical systems in the quantum regime, such as low mechanical and dielectric losses. The flip side of this is to imagine using optomechanics or electromechanics to revisit the novel physics of superfluid helium, including bosonic helium-4 and fermionic helium-3. In particular, when spatially restricted in one dimension, helium superfluids are expected to demonstrate quasi-two dimensional behavior with qualitatively different physics than in three dimensions. By using nanofabrication techniques to both confine the helium and provide an electromechanical detection scheme, we are beginning the journey of studying such two-dimensional superfluids.
Superfluid Helium Electromechanics
Professor John Davis
Associate Professor
University of Alberta
Department of Physics
Title: Superfluid Helium Electromechanics
Abstract: Liquid helium posses many properties that make it an attractive medium for studies of mechanical systems in the quantum regime, such as low mechanical and dielectric losses. The flip side of this is to imagine using optomechanics or electromechanics to revisit the novel physics of superfluid helium, including bosonic helium-4 and fermionic helium-3. In particular, when spatially restricted in one dimension, helium superfluids are expected to demonstrate quasi-two dimensional behavior with qualitatively different physics than in three dimensions. By using nanofabrication techniques to both confine the helium and provide an electromechanical detection scheme, we are beginning the journey of studying such two-dimensional superfluids.
TBA
Dr. Allen Scheie
Postdoctoral Research Associate
Oak Ridge National Laboratory
Neutron Scattering Division
Title: Witnessing entanglement in quantum magnets using neutron scattering
Abstract: In this talk I show how information about solid state quantum entanglement can be extracted from magnetic neutron scattering using model-independent techniques. Using the 1D spin chain KCuF3, we examine three entanglement witnesses applicable to neutron scattering: one tangle, two tangle, and Quantum Fisher Information (QFI). We find that QFI is the most experimentally robust, giving good agreement between theory and experiment over all measured temperatures, and witnessing multipartite entanglement up to 75 K. We then apply the entanglement witnesses to the 2D triangular lattice KYbSe2, showing the presence of appreciable entanglement in the low temperature phase. We then use diffuse scattering fits, heat capacity comparisons, and nonlinear spin wave fits to demonstrate that KYbSe2 is proximate to a quantum spin liquid. We thus provide a rigorous route to studying and understanding highly entangled quantum phases.
TBA
Dr. Allen Scheie
Postdoctoral Research Associate
Oak Ridge National Laboratory
Neutron Scattering Division
Title: Witnessing entanglement in quantum magnets using neutron scattering
Abstract: In this talk I show how information about solid state quantum entanglement can be extracted from magnetic neutron scattering using model-independent techniques. Using the 1D spin chain KCuF3, we examine three entanglement witnesses applicable to neutron scattering: one tangle, two tangle, and Quantum Fisher Information (QFI). We find that QFI is the most experimentally robust, giving good agreement between theory and experiment over all measured temperatures, and witnessing multipartite entanglement up to 75 K. We then apply the entanglement witnesses to the 2D triangular lattice KYbSe2, showing the presence of appreciable entanglement in the low temperature phase. We then use diffuse scattering fits, heat capacity comparisons, and nonlinear spin wave fits to demonstrate that KYbSe2 is proximate to a quantum spin liquid. We thus provide a rigorous route to studying and understanding highly entangled quantum phases.
Ultimate-density atomic semiconductor via flat phonon bands
Professor Jun Hee Lee
School of Energy and Chemical Engineering
Ulsan National Institute of Science and Technology
South Korea
Title: Ultimate-density atomic semiconductor via flat phonon bands
Abstract: Dispersion-less flat energy bands in momentum space generate localized states and are known to cause unconventional phenomena such as graphene superconductivity in electrons and individual spin flips in magnons. However flat bands in phonon were not discovered yet. For the first time, we discovered flat bands in phonon exist surprisingly in a ferroelectric HfO2 and produce a localized motion of atoms as if their chemical bond temporarily disappears by an external voltage. With the vanishing bond, each atom can be freely displaced by the voltage for the information storage. Our discovery of the atom control directly in a solid will lead us to the design of ultimate-density memory semiconductors reaching up to ~100 TB [1]. Our theory is directly applicable to the Si-compatible HfO2 so can be materialized in all electronic devices [2]. Just as Einstein’s theory of relativity (E=mc2) enabled us to make bombs out of atoms not out of materials, with our “Atomic Semiconductor” we will open the era of designing memories on an atomic scale rather than a materials scale and carrying a data center in the palm of your hand.
[1] “Scale-free ferroelectricity driven by flat phonon bands in HfO2”, H.-J. Lee et al., Science 369, 1343 (2020).
[2] “A key piece of the ferroelectric hafnia”, B. Noheda et al., Science 369, 1300 (2020).
Ultimate-density atomic semiconductor via flat phonon bands
Professor Jun Hee Lee
School of Energy and Chemical Engineering
Ulsan National Institute of Science and Technology
South Korea
Title: Ultimate-density atomic semiconductor via flat phonon bands
Abstract: Dispersion-less flat energy bands in momentum space generate localized states and are known to cause unconventional phenomena such as graphene superconductivity in electrons and individual spin flips in magnons. However flat bands in phonon were not discovered yet. For the first time, we discovered flat bands in phonon exist surprisingly in a ferroelectric HfO2 and produce a localized motion of atoms as if their chemical bond temporarily disappears by an external voltage. With the vanishing bond, each atom can be freely displaced by the voltage for the information storage. Our discovery of the atom control directly in a solid will lead us to the design of ultimate-density memory semiconductors reaching up to ~100 TB [1]. Our theory is directly applicable to the Si-compatible HfO2 so can be materialized in all electronic devices [2]. Just as Einstein’s theory of relativity (E=mc2) enabled us to make bombs out of atoms not out of materials, with our “Atomic Semiconductor” we will open the era of designing memories on an atomic scale rather than a materials scale and carrying a data center in the palm of your hand.
[1] “Scale-free ferroelectricity driven by flat phonon bands in HfO2”, H.-J. Lee et al., Science 369, 1343 (2020).
[2] “A key piece of the ferroelectric hafnia”, B. Noheda et al., Science 369, 1300 (2020).