BEGIN:VCALENDAR VERSION:2.0 PRODID:Icfo X-PUBLISHED-TTL:P1W BEGIN:VEVENT UID:69d4b40dae05a DTSTART:20250530T100000Z SEQUENCE:0 TRANSP:OPAQUE LOCATION:ICFO Auditorium SUMMARY:ICFO | SERGI BATLLE PORRO CLASS:PUBLIC DESCRIPTION:Since the discovery of graphene\, two-dimensional (2D) material s have garnered significant attention from the condensed matter physics co mmunity owing to their potential to engineer new physical\, optical\, and mechanical properties. The 2D material class now includes insulators (hexa gonal boron nitride\, hBN)\, semiconductors (transition metal dichalcogeni des\, TMDs)\, superconductors (NbSe2)\, topological insulators (Bi2Te3)\, and ferromagnets (CrI3). Beyond their inherent properties\, layered materi als allow for new characteristics through vertical stacking. Recent develo pments have led to the discovery of moiré\; materials\, in which ele ctronic properties are significantly altered by twisting adjacent 2D layer s.\nThe discovery of superconductivity in magic-angle twisted bilayer grap hene (MATBG) marked a milestone in moiré\; physics\, initiating a ra pidly growing field. The resulting phase diagrams of other high-Tc superco nductors\, MATBG\, serve as a platform for exploring highly tunable strong ly correlated states. At a twist angle of approximately 1.1°\;\, the \" magic angle\,&rdquo\; MATBG shows significant band flattening near the Dir ac points\, reducing the Fermi velocity and making the kinetic energy smal ler than the repulsive Coulomb interactions. This results in superconducti vity and various emergent phases dominated by many-body physics\, includin g correlated insulators\, orbital magnetism\, nematic orders\, and topolog ical states.\nMoiré\; materials with large superlattice unit cells f acilitate the exploration of strongly correlated phenomena at low charge c arrier densities. Local back-gate electrodes enable capacitive tuning betw een strongly correlated states in-situ\, a unique feature not available in other high-Tc superconductors. Advances in scanning probe techniques have allowed researchers to determine local properties at the sub-nanometer sc ale. Scattering-type scanning near-field optical microscopy (s-SNOM) is pa rticularly suited for exploring MATBG because it can measure scattering an d photovoltage signals at the nanometer scale while simultaneously probing mesoscopic electron transport. \;\nUtilizing a groundbreaking cryo-ne ar-field nanoscopy method\, we will conduct s-SNOM measurements at cryogen ic temperatures (as low as 8 K) to assess the optical and photovoltage nea r-field responses. This approach employs energies in the mid-infrared (MIR ) and terahertz (THz) ranges\, which align with the anticipated optical tr ansition energies in the band structures of these materials.\nThe primary objectives of this thesis are to ascertain the pertinent optical and therm oelectric coefficients in twisted moiré\; materials\, evaluate the i mpact of inhomogeneities through gate-tuned near-field photovoltage and op tical measurements\, visualize correlated phenomena and broken symmetry st ates\, and comprehend the nature of dephased signals in various measuremen ts. This dissertation seeks to highlight crucial advancements in quantum p hases\, quantum nano-optoelectronics\, and thermoelectricity\, while suppo rting interest in unresolved questions\, such as the characteristics of lo w-temperature correlated states. Additionally\, it outlines future objecti ves for near- and far-field photovoltage experiments.\n \;\nFriday May 30\, 12:00 h. ICFO Auditorium \nThesis Directors: Prof. Dr. Frank Koppens and Dr. Petr Stepanov DTSTAMP:20260407T073645Z END:VEVENT END:VCALENDAR