Title: Very high energy collective modes in fractional quantum Hall fluids: Rise of the parton

Speaker: Prof. Ajit Balram, IMSc Chennai

Abstract: The low-energy physics of fractional quantum Hall (FQH) states -- a paradigm of strongly correlated topological phases of matter -- to a large extent is captured by weakly interacting quasiparticles known as composite fermions. In this talk, I will demonstrate that some high-energy states in the FQH spectra necessitate a different description based on parton quasiparticles. The Jain states at filling factor \nu = n/(2pn \pm 1) with integers n, p \ge 2 support two kinds of collective modes: In addition to the well-known Girvin-MacDonald-Platzman (GMP) mode, they host a high-energy collective mode, which we interpret as the GMP mode of partons. I will elucidate observable signatures of the parton mode in the dynamics following a geometric quench. I will also present a microscopic wave function for the parton mode and demonstrate agreement between its variational energy and exact diagonalization. These results point to partons being ``real" quasiparticles which, in a way reminiscent of quarks, become observable only at sufficiently high energies.