Mechanical Control of Spin States in Spin-1 Molecules and the Underscreened Kondo Effect

Abstract

Spin Control Through Molecular Stretching Molecules with high symmetry, such as metal complexes with several equivalent ligands, can, in principle, have this symmetry broken by stresses that lengthen bonds in one direction. Parks et al. (p. 1370 ; see the Perspective by Jarillo-Herrero ) placed cobalt complexes in a break-junction contact and then applied a mechanical force to slowly open the contact. Low-temperature measurement of differential conductance revealed a splitting of the Kondo peak at zero-applied voltage into two features, which occurred by breaking the degeneracy of S = 1 triplet states. This assignment of the spin state was confirmed by the evolution of splitting with magnetic field and by comparison to theory for a case where the conduction electrons only partially screen the spin states.