Propagation Modes in Heisenberg Spin Glasses

Spin glasses is a fascinating field, from which a variety of theoretical models and concepts were invented. As an emergent state from the random magnetic system, it defers from other statistical systems in several ways. In particular, the quenched variables prevent the system to be ergodic, and the competitive interactions gives rise to non-trivial degeneracies of the ground states as well as the excitations. In this essay, I will briefly discuss these generic features of spin glasses by presenting some of the characteristic experimental results followed by theoretic analysis. The broken symmetries are discussed with compare to other magnetic systems. Hydrodynamic theory, as well as numerical investigations are discussed aiming to identify the low lying excitations.