Novel orientational ordering and reentrant metallicity in K(x)C(60) monolayers for 3 < or = x < or = 5

• Published in: Physical review letters Vol. 99; no. 8; p. 086402
• Main Authors: Wang, Yayu, Yamachika, R, Wachowiak, A, Grobis, M, Khoo, K H, Lee, D-H, Louie, Steven G, Crommie, M F
• Format: Journal Article
• Language: English
• Published: United States 24-08-2007
• Subjects: Electrons; Metals - chemistry; Transition Elements
• ISSN: 0031-9007

STM studies on K(x)C(60) monolayers reveal new behavior over a wide range of the phase diagram. As x increases from 3 to 5 K(x)C(60) monolayers undergo metal-insulator-metal reentrant phase transitions and exhibit a variety of novel orientational orderings, including a complex 7-molecule, pinwheel-like structure. The proposed driving mechanism for the orientational ordering is the lowering of electron kinetic energy by maximizing the overlap of neighboring molecular orbitals. In insulating (metallic) K(x)C(60) this gives rise to orbital versions of the superexchange (double-exchange) interaction.