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Events on Thursday, February 22nd, 2024

R. G. Herb Condensed Matter Seminar
Superconductor — Insulator Transition and Coulomb drag in non-Fermi-Liquid modelled by an array of SYK grains
Time: 10:00 am - 6:00 pm
Place: 5310 Chamberlin
Speaker: Alexander Chudnovskiy, Hamburg
Abstract: We present a model of a strongly correlated system with a non-Fermi liquid high temperature phase. Its ground state undergoes an insulator to superconductor quantum phase transition (QPT) as a function of a pairing interaction strength. Both the insulator and the superconductor are originating from the same interaction mechanism. The resistivity in the insulating phase exhibits the activation behavior with the activation energy, which goes to zero at the QPT. This leads to a wide quantum critical regime with an algebraic temperature dependence of the resistivity. Upon raising the temperature in the superconducting phase, the model exhibits a finite temperature phase transition to a Bose metal phase, which separates the superconductor from the non-Fermi liquid metal. Furthermore, in the high-temperature non-Fermi-liquid phase, we analyse Coulomb drag and near-field heat transfer in a double-layer system of incoherent metals. The absence of quasiparticles in the strange metal leads to temperature-independent drag resistivity, which is in strong contrast with the quadratic temperature dependence in the Fermi liquid regime. We show that all parameters of the theoretical model can be independently measured in near-field heat transfer experiments, performed in Fermi liquid and strange metal regimes.
Host: Alex Levchenko
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Wisconsin Quantum Institute Seminar
Exploring many-body problems with arrays of individual atoms
Time: 3:30 pm - 5:00 pm
Place: Discovery Building, DeLuca Forum
Speaker: Antoine Browaeys, Laboratoire Charles Fabry, Institut d’Optique, CNRS

Over the last twenty years, physicists have learned to manipulate individual quantum objects: atoms, ions, molecules, quantum circuits, electronic spins... It is now possible to build "atom by atom" a synthetic quantum matter. By controlling the interactions between atoms, one can study the properties of these elementary many-body systems: quantum magnetism, transport of excitations, superconductivity... and thus understand more deeply the N-body problem. More recently, it was realized that these quantum machines may find applications in the industry, such as finding the solution of combinatorial optimization problems.

This seminar will present an example of a synthetic quantum system, based on laser-cooled ensembles of individual atoms trapped in microscopic optical tweezer arrays. By exciting the atoms into Rydberg states, we make them interact, even at distances of more than ten micrometers. In this way, we study the magnetic properties of an ensemble of more than a hundred interacting ½ spins, in a regime in which simulations by usual numerical methods are already very challenging. Some aspects of this research led to the creation of a startup, Pasqal.

This event starts at 3:30pm with refreshments, followed at 3:45pm by a short presentation by Atharva Vidwans (MSPQC student Micheline Soley group) titled "qDRIVE: A Variational Quantum Eigensolver for Resonance Identification on Near-Term Computers". The invited presentation starts at 4pm.

Host: Mark Saffman
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Astronomy Colloquium
Building Planetary Systems: The Formation of Planetesimals
Time: 3:30 pm - 4:30 pm
Place: 4421 Sterling Hall
Speaker: Jake Simon, Iowa State University
Abstract: Planetesimals are small rocky (and sometimes icy) objects, typically 1-100 km in diameter (e.g., asteroids and comets in the Solar System). One of the largest unanswered questions in all of planetary astrophysics is: how do these planetesimals form in the disks that orbit young, newly forming stars (“circumstellar disks”)? In this talk, I will discuss my group’s research projects devoted to answering this important question. I will first provide an overview of planet formation and describe how planetesimals are an integral step in the planet formation process. I will then discuss the progress my group has made in understanding planetesimal formation with theoretical and computational models. In particular, by using computational fluid and particle dynamics, run on large-scale supercomputing facilities, we are working towards understanding under what conditions and in what locations planetesimals can or cannot form in circumstellar disks. I will conclude with a set of future goals to connect what we have learned so far to the larger picture of planet formation.
Host: Ke Zhang
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