Gossamer condensates and spin orbit localization in f-electron materials

George Chapline, Lawrence Livermore National Laboratory

Abstract: A hint that quantum criticality plays an important role in the actinides is that as a function of relatively modest changes in temperature and pressure there is a plethora of complex phase transitions in elemental Np, Pu, and Am that involve changes in both the lattice structure and the electronic organization of the 5f electrons. However, in this case the quantum critical behavior cannot be due to the Kondo effect since there are no local moments in Pu. A promising idea is to assume that there are gossamer pairing correlations for the conduction f-electrons. Actually the elemental actinides are anti-ferromagnetically ordered above Cm while Am, Am/Pu, and certain Pu compounds exhibit exotic superconductivity. This is reminiscent of the "gossamer" superconductivity in the cuprates and suggests that the ground states of the actinides have BCS-like pairing correlations. A more general idea [1] is that there is a gossamer condensate in all materials that have metal to bad metal transitions similar to the volume collapse transitions in the rare earths and actinides. The physical origin of the gossamer condensate in f-electron materials may be spin orbit effects [2]. While it is well known that spin orbit effects are important for core states in f-electron materials, spin orbit effects may also be important for conduction states if the screening length is not too small and lattice distortions give rise to a local electric field. Under these circumstances the charge carriers are solitons and carry a monopole-like charge. [1] Phil. Mag. 85, 867 (2005) [2] Phil. Mag. 86, 1201 (2006)