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DTSTART;TZID=Europe/Paris:20240905T140000
DTEND;TZID=Europe/Paris:20240905T153000
DTSTAMP:20260417T143707
CREATED:20240828T065637Z
LAST-MODIFIED:20240902T071424Z
UID:10904-1725544800-1725550200@fermi.univ-tlse3.fr
SUMMARY:Real-time time-dependent density functional theory for nanoplasmonics : Neutral and charged nanowire dimers. - (Lorenzo Stella / LPT / Seminar). - 5/09/2024\, 14H
DESCRIPTION:Lorenzo Stella (Université Queen’s de Belfast) \nSeminar LPT\, 5/09/2024\, 14H\, 3R1\, seminar room\, 3rd floor \nAbstract :  \nPlasmons are electron density oscillations with respect to the ionic background. Metal and heavily doped semiconductors can support volume\, surface and localised plasmon modes. In plasmonic devices\, plasmonic modes are used\, e.g.\, for chemical sensing\, promoting catalysis and localised heating. Numerical modelling of plasmonic devices is routinely done by solving macroscopic Maxwell equations\, given a suitable parametrisation of the material (metal and dielectric) permittivities. \nAt the nanoscale\, numerical models based on macroscopic permittivities are no longer reliable. At this scale\, time-dependent density functional theory (TDDFT) within the adiabatic local density approximation (ALDA) already provides a reliable description of the electron density oscillations\, including subtle effects due to electron spill-out and tunnelling. \nIn this talk\, I will illustrate the application of TDDFT to nanoplasmonics using a nanowire dimer as a test-case. Well-known results for the plasmon resonance evolution of neutral dimers as a function of the nanowire distance will be compared with more recent results for their charged counterparts. Our real-time TDDFT results suggest that oppositely charged nanowires form a « nanocapacitor » which can « discharge » by means of a charge-transfer current through the gap. \n 
URL:https://fermi.univ-tlse3.fr/event/tba-lorenzo-stella-lpt-seminar-5-09-2024-14h/
LOCATION:salle de séminaire 3ème étage\, Bâtiment 3r1 Université Toulouse III\, Toulouse\, 31400\, France
CATEGORIES:Events,LPT,Seminars
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20240910T140000
DTEND;TZID=Europe/Paris:20240910T153000
DTSTAMP:20260417T143707
CREATED:20240824T082047Z
LAST-MODIFIED:20240829T082333Z
UID:10944-1725976800-1725982200@fermi.univ-tlse3.fr
SUMMARY:Information theory bounds on randomness-based phase transitions. - (Noa Feldman / LPT / Seminar). - 10/09/2024\, 14H
DESCRIPTION:Noa Feldman(Université de Tel Aviv) \nSeminar LPT\, 10/09/2024\, 14H\, 3R1\, seminar room\, 3rd floor \nAbstract : \nWe introduce a new perspective on the connection between many-body physics and information theory. We study phase transitions in models with randomness\, such as localization in disordered systems\, or random quantum circuits with measurements. \nUtilizing information-based arguments regarding probability distribution differentiation\, rigorous results for bounds on critical exponents in such phase transitions are obtained with a minimal amount of work.\nWe first demonstrate our method by rederiving the well known Harris criterion\, bounding \noareal-space and dynamical critical exponents in the Anderson localization transition. \nWe then move to obtain new bounds on critical exponents in many-body Fock space localization transition and localization in Coulomb-interactive models. Somewhat surprisingly\, our bounds are not obeyed by previous studies of these systems\, indicating possible inadequacies in their results\, which we discuss. Finally\, we apply our method to measurement-induced phase transition in random quantum circuits\, obtaining bounds transcending recent mapping to percolation problems. \n&nbsp; \n<hr />
URL:https://fermi.univ-tlse3.fr/event/information-theory-bounds-on-randomness-based-phase-transitions-noa-feldman-lpt-seminar-10-09-2024-14h/
LOCATION:salle de séminaire 3ème étage\, Bâtiment 3r1 Université Toulouse III\, Toulouse\, 31400\, France
CATEGORIES:Events,LPT,Seminars
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20240917T140000
DTEND;TZID=Europe/Paris:20240917T153000
DTSTAMP:20260417T143707
CREATED:20240916T090923Z
LAST-MODIFIED:20240916T135235Z
UID:10915-1726581600-1726587000@fermi.univ-tlse3.fr
SUMMARY:From moiré to moiré-of-moiré states and their topologies in helical twisted trilayer graphene. - (Yuncheng Mao / LPT / Seminar). - 17/09/2024\, 14H
DESCRIPTION:Yuncheng Mao (CINaM\, Marseille) \nSeminar LPT\, 17/09/2024\, 14H\, 3R1\, seminar room\, 3rd floor \nAbstract \nThe experimental and theoretical success in twisted bilayer graphene (TBG) opened a new domain in modern condensed physics\, now called « twistronics ». Such 2D vdW heterostructures offer various platforms for the study of strongly correlated materials and hopefully topologically protected high-temperature superconductivity\, paving the way to topological quantum computation and information in the future. Equipped with overly rich symmetries\, different quantum topologies also emerge in such systems. A close cousin to TBG is the twisted trilayer graphene (TTG). With only an additional graphene layer\, TTG exhibits significantly different properties than TBG\, with even higher tunability as well as distinct symmetries and topologies. We are especially interested in the helical twisted trilayer graphene (hTTG) where the top and bottom layers are rotated in opposite directions with respect to the middle layer. In this case\, two moiré patterns between neighboring layers coexist and are in general incommensurate. Therefore\, the mismatch between the two moiré periodicities gives rise to a higher-level moiré pattern on top of the moiré patterns\, referred to as the « moiré-of-moiré » or « supermoiré » pattern. With proper approximations\, we can ignore the supermoiré variations and access the electronic state at moiré scale. Interesting topological phase transition associated with the variation of twist angle and the stacking is identified. To evaluate the supermoiré states\, a theoretical framework is devised to treat it in the context of perturbed periodicity. This framework is quite general and can be applied to other physical systems. The supermoiré states can be obtained for certain twisted angles close to rational ratios. A pseudo-magnetic field effect due to the supermoiré modulation is revealed\, which is otherwise invisible by the trivial average of moiré properties over the supermoiré length scale. \nReferences : \n[1] Y. Mao\, D. Guerci\, and C. Mora\, Supermoiré low-energy effective theory of twisted trilayer graphene\, Phys. Rev. B 107\, 125423 (2023). \n[2] D. Guerci\, Y. Mao\, and C. Mora\, Chern mosaic and ideal flat bands in equal-twist trilayer graphene\, Phys. Rev. Research 6\, L022025 (2024). \n[3] D. Guerci\, Y. Mao\, and C. Mora\, Nature of even and odd magic angles in helical twisted trilayer graphene\, Phys. Rev. B 109\, 205411 (2024).
URL:https://fermi.univ-tlse3.fr/event/tba-yuncheng-mao-lpt-seminar-17-09-2024-14h/
LOCATION:salle de séminaire 3ème étage\, Bâtiment 3r1 Université Toulouse III\, Toulouse\, 31400\, France
CATEGORIES:Events,LPT,Seminars
END:VEVENT
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