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Polymorphism control of superconductivity and magnetism in Cs3C60 close to the Mott transition

DOI: 10.1038/nature09120 DOI Help

Authors: Alexey Ganin (University of Liverpool) , Yasuhiro Takabayashi (University of Durham) , Peter Jeglic (Institute Jožef Stefan) , Denis Arcon (Institute Jožef Stefan) , Anton Potocnik (Institute Jožef Stefan) , Peter Baker (ISIS Pulsed Neutron and Muon Source) , Yasuo Ohishi (Japan Synchrotron Radiation Research Institute, SPring-8) , Martin Mcdonald (Durham University) , Manolis Tzirakis (Durham University) , Alec Mclennan (University of Liverpool) , George Darling (University of Liverpool) , Masaki Takata (Japan Synchrotron Radiation Research Institute, SPring-8) , Matthew Rosseinsky (University of Liverpool) , Kosmas Prassides (University of Durham)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Nature

State: Published (Approved)
Published: May 2010
Diamond Proposal Number(s): 731

Abstract: The crystal structure of a solid controls the interactions between the electronically active units and thus its electronic properties. In the high-temperature superconducting copper oxides, only one spatial arrangement of the electronically active Cu2+ units—a two-dimensional square lattice—is available to study the competition between the cooperative electronic states of magnetic order and superconductivity1. Crystals of the spherical molecular C603- anion support both superconductivity and magnetism but can consist of fundamentally distinct three-dimensional arrangements of the anions. Superconductivity in the A3C60 (A = alkali metal) fullerides has been exclusively associated with face-centred cubic (f.c.c.) packing of C603- (refs 2, 3), but recently the most expanded (and thus having the highest superconducting transition temperature, Tc; ref. 4) composition Cs3C60 has been isolated as a body-centred cubic (b.c.c.) packing, which supports both superconductivity and magnetic order5, 6. Here we isolate the f.c.c. polymorph of Cs3C60 to show how the spatial arrangement of the electronically active units controls the competing superconducting and magnetic electronic ground states. Unlike all the other f.c.c. A3C60 fullerides, f.c.c. Cs3C60 is not a superconductor but a magnetic insulator at ambient pressure, and becomes superconducting under pressure. The magnetic ordering occurs at an order of magnitude lower temperature in the geometrically frustrated f.c.c. polymorph (Néel temperature TN = 2.2 K) than in the b.c.c.-based packing (TN = 46 K). The different lattice packings of C603- change Tc from 38 K in b.c.c. Cs3C60 to 35 K in f.c.c. Cs3C60 (the highest found in the f.c.c. A3C60 family). The existence of two superconducting packings of the same electronically active unit reveals that Tc scales universally in a structure-independent dome-like relationship with proximity to the Mott metal–insulator transition, which is governed by the role of electron correlations characteristic of high-temperature superconducting materials other than fullerides.

Subject Areas: Physics, Materials

Instruments: I11-High Resolution Powder Diffraction