Condensed Matter Seminar
Spectral gaps and dynamical transitions in random open quantum systems
Prof. Dror Orgad
HUJI
Mon, 28 Apr 2025, 11:10
Sacta-Rashi Building for Physics (54), room 207
Abstract: The relaxation of nonequilibrium systems to their steady states, and especially the universal
features of such dynamics, is of considerable interest. In this talk I will discuss the relaxation
rate of a chaotic quantum system coupled to noise, using a model where the Hamiltonian and the
system-noise coupling are described by random matrices whose entries decay as power laws of distance.
I will show that the rate exhibits three phases depending on the exponents of the power laws:
a phase where the approach is asymptotically exponential as a result of a gap in the spectrum of the
Liouvillian superoperator that generates the dynamics, and two gapless phases with subexponential
relaxation, distinguished by the manner in which the gap decreases with system size. I will also
describe several spectral features emerging in the limits of weak and strong decoherence.
Physics Colloquium
Topologies in surface waves: Conservation laws, Field textures and new Quantum correlations
Guy Bartal
Technion
Tue, 29 Apr 2025, 12:00
Ilse Katz Institute for Nanoscale Science & Technology (51), room 015
Abstract: Surface waves are three-dimensional vector-field bound to a two-dimensional surface. Structuring such waves provides access to new topologies and textures of electro-magnetic waves, typically not found in propagating waves. For example, the separability of spin and orbital angular momentum in photons propagating in free space does not hold for nanophotonic states. Instead, such states, e.g., surface plasmons, can only be defined by their total angular momentum (TAM), resulting in both classical and quantum implications. Those include unique conservation laws, which apply to both circularly-symmetric, periodic and quasi-periodic nanophotonic states, well-recognized field textures – such as optical skyrmions, and new quantum correlations between photon pairs.
I will review our experimental investigation of new topologies and conservation rules emanating from the unique properties of surface waves. Those include Optical skyrmions - topological defects in 3D vector field bound to a 2D surface, higher-dimensional topology and conservation laws in plasmonic quasi-lattices and non-classical correlations between plasmon pairs entangled in their total angular momentum.
References
1. Shai Tsesses, Evgeny Ostrovsky, Kobi Cohen, Bergin Gjonaj, Netanel H. Lindner, Guy Bartal, “Optical skyrmion lattice in evanescent electromagnetic fields”, Science 361 (6406), 993-996 (2018)
2. Shai Tsesses, Kobi Cohen, Evgeny Ostrovsky, Bergin Gjonaj and Guy Bartal, “Spin–Orbit Interaction of Light in Plasmonic Lattices”, Nanoletters 19, 6, 4010-4016 (2019)
3. Shai Tsesses, Pascal Dreher, David Janoschka, Alexander Neuhaus, Kobi Cohen, Tim C Meiler, Tomer Bucher, Shay Sapir, Bettina Frank, Timothy J Davis, Frank Meyer zu Heringdorf, Harald Giessen, Guy Bartal, Four-dimensional conserved topological charge vectors in plasmonic quasicrystals, Science 387, 644 (2025)
4. Amit Kam, Shai Tsesses, Yigal Ilin, Kobi Cohen, Yaakov Lumer, Lior Fridman, Stav Lotan, Anatoly Patsyk, Liat Nemirovsky-Levy, Meir Orenstein, Mordechai Segev, Guy Bartal, Near-field photon entanglement in total angular momentum, Nature 640, 634 (2025)
*** Refreshments at 12:00, talk at 12:15.
