On Larkin-Imry-Ma State of 3He-A in Aerogel

Abstract

Superfluid 3He-A shares the properties of spin nematic and chiral orbital ferromagnet. Its order parameter is characterized by two vectors \(\hat{\textbf{d}}\) and \(\hat{\textbf{l}}\) . This doubly anisotropic superfluid, when it is confined in aerogel, represents the most interesting example of a system with continuous symmetry in the presence of random anisotropy disorder. We discuss the Larkin-Imry-Ma state, which is characterized by the short-range orientational order of the vector \(\hat{\textbf{l}}\) , while the long-range orientational order is destroyed by the collective action of the randomly oriented aerogel strings. On the other hand, sufficiently large regular anisotropy produced either by the deformation of the aerogel or by applied superflow suppresses the Larkin-Imry-Ma effect leading to the uniform orientation of \(\hat{\textbf{l}}\) . The interplay of regular and random anisotropy allows us to study many different effects.