Talks

Composite fermion (CF) is a topological quasiparticle that emerges from a non-perturbative attachment of vortices to electrons in strongly correlated two-dimensional materials. Similar to non-interacting fermions that form Landau levels in a magnetic field, CFs can fill analogous ``Lambda'' levels, giving rise to the fractional quantum Hall (FQH) effect of electrons. Here, we show that Lambda levels can be directly visualized through the characteristic peak structure in the signal obtained via spectroscopy with the scanning tunneling microscopy (STM) on a FQH state. Complementary to transport, which probes low-energy properties of CFs, we show that \emph{high-energy} features in STM spectra can be interpreted in terms of Lambda levels. We numerically demonstrate that STM spectra can be accurately modeled using Jain's CF theory. Our results show that STM provides a powerful tool for revealing the anatomy of FQH states and identifying physics beyond the non-interacting CF paradigm.

Interaction between the electrons and phonons determines some of the most fundamental properties of solids, including superconductivity, thermal and thermoelectric transport, polaronic effects, and electrical resistance in metal at high temperatures. In good metals, particularly noble metals such as gold (Au), silver (Ag), or copper (Cu), the coupling of electrons and phonons is rather weak [1], and the electron-phonon coupling constant () is small. The corresponding electron-
phonon scattering rate provides an excellent quantitative description of the metallic resistivity when the temperature () exceeds the Debye temperature (). The regime of however, remained experimentally inaccessible so far, raising questions on possible universal Planckian bound on scattering rate [2], polaronic deformation, or indeed, even the stability of a metallic state itself [3]. In this work [6], we demonstrate how coulomb interactions at the nanoscale interface of Au and Ag (of
radius nm) [4] that allow...

Recent technological advancements have enabled the preservation of near-perfect superconductivity and lattice structure in isolated, atomically thin Bi2Sr2CuCa2O8+δ (Bi-2212) crystals, facilitating the development of Bi-2212-based junctions [1,2]. These advancements focus on controlling the diffusion of oxygen interstitials, a key factor causing disorder in Bi-2212 cuprates. While intrinsic local lattice distortions in pristine cuprates [3] may contribute minimally without affecting the d-wave nature of the dominant order parameter, lattice distortions due to oxygen interstitials diffusion above 200 K [4,5] are detrimental. To counter this, a cryogenic stacking protocol has been developed, freezing oxygen interstitial motion at temperatures well below 200 K and rapidly establishing the interface in an ultra-low moisture environment [6-8]. This method has led to the creation of artificial intrinsic Josephson junctions, which show a strong dependence of Josephson energy on the twist angl...