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DTSTART;TZID=Europe/Paris:20250107T140000
DTEND;TZID=Europe/Paris:20250107T150000
DTSTAMP:20260413T133948
CREATED:20250102T103455Z
LAST-MODIFIED:20250102T103605Z
UID:11322-1736258400-1736262000@fermi.univ-tlse3.fr
SUMMARY:Localization enhancement in gain-loss non-Hermitian disordered models. - (Ivan Khaymovich / LPT / Seminar). - 07/01/2025\, 14H
DESCRIPTION:Séminaire LPT \nIvan Khaymovich (Nordita\, Stockholm) \nSeminar LPT\, 07/01/2025\, 14H\, 3R4\, salle de conférence \nSummary \nRecently the interest in non-Hermitian disordered models has been revived\, due to the claims of instability of a many-body localization to a coupling to a bath.\nTo describe such open quantum systems\, one often focuses on an energy leakage to a bath\, using effective non-Hermitian Hamiltonians. A well-known Hatano-Nelson model [1]\, being a 1d Anderson localization (AL) model\, with different hopping amplitudes to the right/left\, shows AL breakdown\, as non-Hermiticity suppresses the interference. \nUnlike this\, we consider models with the complex gain-loss disorder and show that in general these systems tend to the localization due to non-Hermiticity. \nFirst\, we consider a power-law random banded matrix ensemble (PLRBM) [2]\, known to show AL transition (ALT) at the power of the power-law hopping decay a=d equal to the dimension d. In [3]\, we show that a non-Hermitian gain-loss disorder in PLRBM shifts ALT to smaller values d/2 \nA similar effect of the reduced critical disorder due to the gain-loss complex-valued disorder has been recently observed by us numerically [4]. In order to analytically explain the above numerical results\, we derive an effective non-Hermitian resonance counting and show that the delocalization transition is driven by so-called « bad resonances »\, which cannot be removed by the wave-function hybridization (e.g.\, in the renormalization group approach)\, while the usual « Hermitian » resonances are suppressed. In the last part\, if time permits\, I will consider the effects of non-Hermitian diagonal disorder on many-body localization in interacting systems and the localization in quantum random energy model [5] and show that the above paradigm also works there. \nReferences \n[1] N. Hatano\, D. R. Nelson\, « Localization Transitions in Non-Hermitian Quantum Mechanics »\, Phys. Rev. Lett. 77\, 570 (1996). \n[2] A. D. Mirlin\, Y. V. Fyodorov\, F.-M. Dittes\, J. Quezada\, and T. H. Seligman\, « Transition from localized to extended eigenstates in the ensemble of power-law random banded matrices »\, Phys. Rev. E 54\, 3221–3230 (1996). \n[3] G. De Tomasi\, I. M. K. « Non-Hermiticity induces localization : good and bad resonances in power-law random banded matrices »\, Phys. Rev. B 108\, L180202 (2023).\n\n[4] L. S. Levitov « Absence of localization of vibrational modes due to dipole-dipole interaction »\, Europhys. Lett. 9\, 83 (1989). \n[5] G. De Tomasi\, I. M. K. « Stable many-body localization under random continuous measurements in the no-click limit »\, Phys. Rev. B 109\, 174205 (2024). \n 
URL:https://fermi.univ-tlse3.fr/event/localization-enhancement-in-gain-loss-non-hermitian-disordered-models-ivan-khaymovich-lpt-seminar-07-01-2025-14h/
LOCATION:Salle de conférence\, Bâtiment 3R4
CATEGORIES:Events,LPT,Seminars
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DTSTART;TZID=Europe/Paris:20250114T140000
DTEND;TZID=Europe/Paris:20250114T153000
DTSTAMP:20260413T133948
CREATED:20250109T093330Z
LAST-MODIFIED:20250110T095511Z
UID:11212-1736863200-1736868600@fermi.univ-tlse3.fr
SUMMARY:Simulateurs quantiques : perspective pointilliste sur la physique à N corps. - (Eugene Demler / LPT / Seminar). - 14/01/2025\, 14H
DESCRIPTION:Séminaire LPT \nEugene Demler (ETH) \nSeminar LPT\, 14/01/2025\, 14H\, 3R4\, salle de conférence \nSummary : I will discuss recent progress of the optical lattice emulators of the Fermi Hubbard model. The new feature of these experiments is availability of snapshots of many-body states with single particle resolution. I will review new insights from these experiments on the properties of doped Mott insulators\, including demonstration of magnetically mediated pairing. I will discuss how experiments with cold atoms provide new perspective on kinetic magnetism in moire materials.
URL:https://fermi.univ-tlse3.fr/event/tba-eugene-demler-lpt-seminar-14-01-2025-14h/
LOCATION:Salle de conférence\, Bâtiment 3R4
CATEGORIES:Events,LPT,Seminars
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