In this talk, I will report our recent experimental study of the Lipkin-Meshkov-Glick model using ultracold gases of Dysprosium atoms, where each atom carries an electronic spin J = 8, equivalent to a set of 16 elementary spins 1/2. The infinite-range Ising interaction is simulated via the quadratic Zeeman light shift produced by an off-resonant laser beam. By varying the interaction strength, we measure a crossover between paramagnetic and ferromagnetic behaviours, separated by a quantum critical regime in which the system exhibits non-classical behaviour. Thanks to a single-spin resolution detection we are able to measure most microscopic properties of the system: magnetisation, eigenstates energies, spin pair correlators and parity. In the ferromagnetic phase, we measure coherent oscillations between the two broken parity states close enough to the critical point and, probe the spontaneous breaking of the Z2 parity symmetry.
Host: Nir Navon (email@example.com)