Seminar
 Thursday 12:4513:45
 Room ESB 235
 Each seminar will feature a 30 min talk by a member of the CMP group about their research and a subsequent informal discussion. This is a fantastic opportunity to get to know your fellow CMP colleagues and start collaborations. Occasionally we also host invited speakers.
Schedule
 April 13, 2023 online
David Moser (Technical University Dresden)
"Quasiuniversality from allinallout Weyl quantum criticality in pyrochlore iridates"
We identify an exotic quasiuniversal behavior near the allinallout Weyl quantum critical point in threedimensional Luttinger semimetals, such as the pyrochlore iridates R2Ir2O7, with R a rareearth element. The quasiuniversal behavior is characterized by power laws with exponents that vary slowly over several orders of magnitude in energy or length. However, in contrast to the quasiuniversality discussed in the context of deconfined criticality, the present case is characterized by a genuinelyuniversal ultralowtemperature behavior. In this limit, the pertinent critical exponents can be computed exactly within a renormalization group analysis. Experimental implications for the pyrochlore iridates are outlined.
 March 23, 2023
Santanu Dey (Maciejko group)
"Fielddriven transition from quantum spin liquid to symmetrybreaking order in triangularlattice antiferromagnets"
 March 16, 2023
Frank Marsiglio
What some of my undergraduate students did in the summer (circa 20152016)*
This talk is about the behaviour of electrons in solids, and is a report of research performed with undergraduates on various projects. I will talk about electron band structure, the pseudopotential effect, double wells and their connection to "bigger" crystals, about deriving tightbinding band structure parameters in simple cases, and about one origin of electronhole asymmetry.
*WARNING: almost all of this talk will be accessible to undergraduates
 March 9, 2023
Michael Buchhold (University of Cologne)
"MeasurementInduced Phase Transitions of Fermions: Phenomenology, Effective Theory and Strategies to Reveal Them"
A wave function exposed to measurements undergoes pure state dynamics, with deterministic unitary and probabilistic measurementinduced state updates. For manyparticle systems, the competition of these different elements gives rise to a scenario similar to quantum phase transitions, which are visible in the entanglement structure of the wave functions. They are masked, however, in standard quantum mechanical observables due to the randomness of measurement outcomes. We study the dynamics of locally measured free fermions in (1+1) dimensions undergoing a measurementinduced phase transition. We strengthen the analogy between this transition and ground state quantum phase transitions by examining a replica field theory for the nth moment of the measured wave function: the phase transition corresponds to a macroscopic change in the dark state wave function of a nonHermitian Hamiltonian. In a second step, we introduce a general strategy to make measurementinduced transitions observable. It relies on breaking the measurement degeneracy explicitly by steering the system towards a chosen representative state. This strategy introduces a unique dark or absorbing state and creates a link of measurementinduced phase transitions to new forms of quantum absorbing state transitions, which can be detected by standard means via a local order parameter.
 Feburary 23, 2023
No seminar (reading week)
 Feburary 9, 2023
Igor Herbut (Simon Fraser University)
"Multiband superconductivity and breaking of timereversal symmetry: theory of BogoliubovFermi surfaces"
Standard singleband electronic systems form superconducting states which exhibit either a full energy gap, gapless points, or gapless lines in the momentum space. It therefore came as a surprise when it was shown by Agterberg, Brydon, and Timm in 2017 that in the case of multiband materials the spectrum of Bogoliubov quasiparticles in the superconducting state can be gapless over entire (albeit small) surfaces in the momentum space. The necessary condition for the appearance of such ``BogoliubovFermi surfaces", was believed to be the breaking of timereversal symmetry and the presence of (unbroken) inversion symmetry. I will show that while the former condition is indeed necessary, the latter is not. A simple unifying theory of the formation of the BogoliubovFermi surfaces with and without inversion symmetry will be presented, and some curious analogies with special relativity in the former case will be pointed out. Finally, time permitting, a possible instability of the inversionsymmetric BogoliubovFermi surface due to residual interactions will be discussed.
 Feburary 2, 2023
Javad Shabani (New York University)
"Towards realization of protected qubits using topological superconductivity"
A central goal in quantum computing research is to protect and control quantum information from noise. This talk will provide recent progress on the developing field of topological superconductivity where we can encode information in spatially separated Majorana zero modes (MZM). We show that topological superconductivity can be achieved in certain hybrid materials where the topological properties are not found in the constituent materials. These special MZMs are formed at the location of topological defects (e.g. boundaries, domain walls, ...) and manifest nonAbelian braiding statistics that can be used in noisefree unitary gate operations. We show by engineering a reconfigurable domain walls on a Josephson junction we can create a scalable platform to study MZM properties and their applications in quantum information science.
 November 24, 2022
Robert Wolkow
"An Introduction to AtomDefined Silicon Quantum Devices and UltraFast, UltraLow Power Classical Circuits"
 November 17, 2022
Howe Simpson (Hegmann Group)
"Measuring Ultrafast Dynamics on the Nanoscale: The Terahertz Scanning Tunneling Microscope"
 November 10, 2022
no seminar (reading week)
 November 3, 2022
Shankar Ganesh (Maciejko Group)
"Describing transitions between topological and conventional symmetrybroken phases"
 October 27, 2022
Alexander Shook (Davis Group)
"Novel Properties of Superfluid 3He Under Nanoscale Confinement"
 October 20, 2022
Michael Dunsmore (Freeman Group)
"Three Axis Torque Investigation of Interfacial Exchange Coupling in a NiFe/CoO Bilayer Magnetic Disk"
 October 13, 2022
no seminar
 October 6, 2022
Canon Sun (Maciejko/Boettcher Group)
"SO(2) theory of confined superfluid He3"
 September 29, 2022
Phong Nguyen (Boninsegni Group)
"Dimensional Crossovers in 2D superfluids"
 September 22, 2022
Santanu Dey (Maciejko Group)
"Quantumcritical electrodynamics of Luttinger fermions"
 December 9, 2021
Aaron Lyons (Woodside Group)
"Characterisation of NonProductive Attempts at Structural Assembly in Single Biomolecules"
 November 18, 2021
Logan Cooke (LeBlanc Group)
"Holonomic Quantum Computing in Ultracold Neutral Atoms via Floquet Engineering"
 November 4, 2021
Pramodh Senarath Yapa (Marsiglio/Maciejko Group)
"Creating a Superfluid Crystal in Helium3"
 October 28, 2021
Clinton Potts (Davis Group)
"Dynamical Backaction Magnomechanics"
 October 21, 2021
Mason Protter (Marsiglio/Maciejko Group)
"NonAbelian gauge structure in driven quantum gasses"
 October 14, 2021
Max Yuan (Wolkow Group)
"Towards the atomic scale readout of acceptor states in pdoped Si"

