Abstract

Electronic systems are at the centre of many of the most important and topical areas of applied science, including materials physics, chemistry, nano-electronics, and quantum computation. The electron liquid paradigm is the foundation of many of our current understanding of these systems’ physical and chemical properties. According to Landau’s Fermi liquid theory, the main properties of the quasiparticle excitations of an electron liquid are embodied in the effective mass, which determines the energy of a single quasiparticle, and the Landau interaction function, which indicates how the energy of a quasiparticle is modified by the presence of other quasiparticles. This simple paradigm underlies our current understanding of the physical and chemical behaviour of metallic systems. The quasiparticle effective mass of the three dimensional homogeneous electron gas has been the subject of theoretical controversy, and there is a lack of experimental data. In this talk, I will present the development of a technique using a stochastic approach to calculate the quasiparticle effective mass of paramagnetic and ferromagnetic electron liquid. The results obtained by the many-body wave function based diffusion quantum Monte Carlo method indicate that the quasiparticle effective mass decreases when the density is reduced, especially in the ferromagnetic case. I will also discuss our new results for the zero-temperature phase diagram of the three-dimensional homogeneous electron gas at very low density. Unlike previous studies, our results show that the electron gas undergoes a first-order quantum phase transition directly from a paramagnetic fluid to a body-centered cubic crystal at density parameter r_s = 86.6(7), with no region of stability for an itinerant ferromagnetic fluid.