Quantum Matter Seminar- Qimiao Si (Rice University)- Loss of Quasiparticles: from Strange Metals to Flat Bands

Abstract: The field of correlation physics continuously expands its horizons. As a primary objective of the field, we aim to determine the organization of the many billions of billions of electrons in the quantum universe of a solid, taking into account both the electrons’ quantum mechanical nature and their electrostatic repulsive interaction. In the standard description, quasiparticle is a central concept. It acts as the adiabatic continuation of a bare electron in the presence of interactions, and is resilient when the interactions are treated perturbatively. In this talk, I will describe how quasiparticles can break apart in the presence of strong correlations [1], and why this loss of quasiparticles promotes high-temperature superconductivity [2]. I will also highlight some of the new frontiers –especially those involving topology [3] and geometry-induced flat bands [4]-- that are being opened up, where a loss of quasiparticles captures new physics.

[1] H. Hu et al., arXiv:2210.14183; Q. Si et al., Nature 413, 804 (2001); S. Paschen & Q. Si, Nat. Rev. Phys. 3, 9 (2021); S. Kirchner et al, Rev. Mod. Phys. 92, 011002 (2020).

[2] H. Hu et al., arXiv:2109.13224.

[3] H. Hu et al., arXiv:2110.06182; L. Chen et al., Nat. Phys. 18, 1341 (2022).

[4] L. Chen et al. arXiv:2307.09431; L. Chen et al, arXiv:2212.08017; H. Hu et al., Sci. Adv. 9, eadg0028 (2023).