[Brahmagupta Physics Colloquium] Very high energy collective modes in fract .." by Prof. Ajit Balram

A talk on "Very high energy collective modes in fractional quantum Hall fluids: Rise of the parton" by 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 ν= n/(2pn±1) with integers n, p≥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.