title: Observation of the ground-state geometric phase in a Heisenberg XY model.
abstract: Geometric phases play a central role in a variety of quantum phenomena, especially in condensed matter physics. Recently, it was shown that this fundamental concept exhibits a connection to quantum phase transitions where the system undergoes a qualitative change in the ground state when a control parameter in its Hamiltonian is varied. Here we report the first experimental study using the geometric phase as a topological test of quantum transitions of the ground state in a Heisenberg XY spin model. Using NMR interferometry, we measure the geometric phase for different adiabatic circuits that do not pass through points of degeneracy.
authors.affiliation: Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China. xhpeng@ustc.edu.cn
authors.forename: Xinhua
authors.initials: X
authors.lastname: Peng
authors.forename: Sanfeng
authors.initials: S
authors.lastname: Wu
authors.forename: Jun
authors.initials: J
authors.lastname: Li
authors.forename: Dieter
authors.initials: D
authors.lastname: Suter
authors.forename: Jiangfeng
authors.initials: J
authors.lastname: Du