Sub-THz Ultrastrong light-matter coupling with Landau levels in semiconductors and superconducting metasurfaces |
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Wpisany przez Jacek Szczytko |
poniedziałek, 09 listopada 2015 20:14 |
Giacomo Scalari ETH Zürich, Institute of Quantum Electronics, Auguste-Piccard-Hof 1, Zürich 8093, Switzerland Szkoła IN : Friday 20th of November 2015, g. 10:15-12:00, room 0.06, Pasteura 5, Faculty of Physics University of Warsaw Cavity light-matter coupling in solid state systems has been recently approaching the ultrastrong coupling regime [1-4], where the Rabi frequency Ω is comparable to the bare excitation frequency ω.. We recently demonstrated a new platform to investigate ultrastrong coupling physics: the cyclotron transition of a 2DEG is coupled to an Au metasurface of THz split-ring resonators reaching the ultrastrong coupling regime and showing record high values of the light-matter coupling ratio Ω / ω =0.58 [5]. I will present our recent advances in this polaritonic system. We employ Nb-based superconducting complementary metasurfaces [6] achieving adiabatic modulation of the polaritonic states through temperature tuning. With the same kind of cavities and a sample with n=4 quantum wells we observe a record‐high normalized coupling ratio of Ω / ω =0.89 [7] at a frequency of 300 GHz. For such value the polaritonic dispersion clearly deviates from the linear regime. I will discuss also an high quality factor complementary THz metasurface based on Niobium thin film [8], whch displays narrow resonance and Q factor higher than 50 at T=3 K in a strongly subwavelength volume ( Vcav/lambda3 of the order of 10-6 ). I will present new experimental results obtained measuring these metasurfaces at temperatures as low as 20 mK, where Q factors as high as 120 are measured. Our measurements highlight the role of the residual normal state electrons at temperatures well below the critical temperature TC [1] C. Ciuti, G. Bastard, and I. Carusotto, Phys. Rev. B 72, 115303 (2005). Szkoła odbywa się dzięki wsparciu projektu POKL UDA – POKL.04.01.01-00-100/10 "Chemia, fizyka i biologia na potrzeby społeczeństwa XXI wieku: nowe makrokierunki studiów I, II i III stopnia" prowadzonemu na Wydziale Chemii UW. |
Poprawiony: środa, 09 grudnia 2015 21:54 |