Louisiana State University Physics & Astronomy

"New properties in old materials: the layered dichalcogenides "

Emilia Morosan
Rice University

Transition metal dichalcogenides have long been known and explored. Due to their reduced dimensionality, such compounds sometimes display charge density wave (CDW) transitions or, upon doping with magnetic ions, often reveal dramatic changes of their physical properties. I will discuss the effects of transition metal intercalation on the properties of two layered chalcogenide materials, TiSe_2 and TaS_2. Although TiSe_2 is one of the first known CDW-bearing materials, the nature of its CDW transition remains controversial. Recently the interest in TiSe_2 has been renewed by our discovery of the new superconducting state (SC) that emerges upon Cu doping. Thus Cu_x TiSe_2 provides the first example of a system in which controlled chemical doping can be used to study the competition between the CDW and SC. I will also discuss experiments on Fe_x TaS_2 aimed at studying the sharp switching of the magnetization that we recently observed in this compound for x = 1/4. For this particular Fe content, Fe_x TaS_2 orders ferromagnetically below 160K and displays very sharp hysteresis loops in the ordered state for H||c. The corresponding magnetoresistance is negative, and qualitatively reproduces the featuees observed in the M(H) data, by showing a sharp drop around the critical field for moment reversal.

Updated: Tue, 18-Mar-2008 3:57 PM