Stripes; Correlated electrons; Superconductivity; Graphite intercalated compounds; Scanning tunneling spectroscopy; Scanning tunneling microscopy; Transition metal dichalcogenides; Charge density waves; Quasiparticle interference imaging
Novello A. M., Hildebrand B., Scarfato A., Didiot C., Monney G., Ubaldini A., Berger H., Bowler D. R., Aebi P., Renner Ch. (2015), Scanning tunneling microscopy of the charge density wave in 1T-TiSe2 in the presence of single atom defects, in PHYSICAL REVIEW B
, 92(8), 081101-1.
Hildebrand B., Didiot C., Novello A. M., Monney G., Scarfato A., Ubaldini A., Berger H., Bowler D. R., Renner C., Aebi P. (2014), Doping Nature of Native Defects in 1T-TiSe2, in PHYSICAL REVIEW LETTERS
, 112(19), 197001-1-197001-5.
Electronic charge and spin segregation into one-directional density waves called stripes is ubiquitous in high temperature superconductor (HTS) copper oxides, in colossal magnetoresistance (CMR) manganese oxides and several other low dimensional electronic oxide materials. Stripes are a particular form of charge density wave (CDW). The interplay between CDWs and superconductivity has been a long standing research focus for a range of superconducting materials whose electronic systems exhibit a reduced dimensionality. The role CDWs play in the occurrence of high temperature superconductivity remains matter of heated debates and subject to experimental scrutiny. Furthermore, fundamental questions about the mechanisms leading to CDW and stripe formation remain open. The challenge of solving the puzzle of "high" temperature superconductivity observed in cuprates, and more recently in iron pnictides, has been driving remarkable developments in theory and experimental techniques, especially scanning tunneling microscopy (STM) and photoemission. However, progresses in STM did so far mostly benefit HTS copper oxides and a range of superconducting materials discovered in their wake (e.g. pnictides and oxichlorides), as well as topological insulators. These materials have attracted much of the community’s attention in recent times. Our three year project is to initiate a new effort following the recent discoveries of charge stripes in a graphite intercalated compound CaC6 and 1T-CuxTiSe2, two low-Tc layered superconductors. Interestingly, they show, along with charge stripes, the highest superconducting transition temperature measured to date in their class. A number of novel experimental findings have brought these materials back into the spotlight. These include significant increase of the superconducting transition temperature, chiral and stripe CDWs, an exciton ground state and remarkable similarities of the CDW and HTS pseudogap phases as observed by ARPES. Our project is to deploy modern scanning probe expertise, especially quasiparticle interference imaging, to contribute to the detailed characterization and understanding of these correlated electron phases and their interaction.