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Superconductivity in CuxTiSe2

Abstract

Charge density waves (CDWs) are periodic modulations of the density of conduction electrons in solids. They are collective states that arise from intrinsic instabilities often present in low-dimensional electronic systems. The most well-studied examples are the layered dichalcogenides–an example of which is TiSe2, one of the first CDW-bearing materials to be discovered. At low temperatures, a widely held belief is that the CDW competes with another collective electronic state, superconductivity. But despite much exploration, a detailed study of this competition is lacking. Here we report how, on controlled intercalation of TiSe2 with Cu to yield CuxTiSe2, the CDW transition can be continuously suppressed, and a new superconducting state emerges near x=0.04, with a maximum transition temperature Tc of 4.15 K at x=0.08. CuxTiSe2 thus provides the first opportunity to study the CDW to superconductivity transition in detail through an easily controllable chemical parameter, and will provide fundamental insight into the behaviour of correlated electron systems.

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Acknowledgements

This research was supported primarily by the US DOE-BES solid state chemistry program, and, in part, by the US NSF MRSEC program.

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Competing interests

The authors declare no competing financial interests.

Correspondence to E. Morosan or R. J. Cava.

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Further reading

Figure 1: Lattice parameters of CuxTiSe2.
Figure 2: Magnetization and transport properties of CuxTiSe2.
Figure 3: The superconducting phase transition as a function of Cu content x.
Figure 4: Characterization of the superconductivity in Cu0.08TiSe2.
Figure 5: Summary of the composition-dependent properties in CuxTiSe2.
Figure 6: The CuxTiSe2 Tx electronic phase diagram.