Dr. Goran Karapetrov [from Drexel University]

Title: Coexistence of Superconductivity and Chiral Charge Density Wave in CuxTiSe2

Time: 14:00 - 15:00, November 5

Place: Conference Room 201, Building 6, HPSTAR (Shanghai)

Host: Mahmod Abdel-Hafiez

Abstract:

TiSe2 is a unique member of dichalcogenides exhibiting chiral charge density waves. Doping with copper or palladium turns this material into a superconductor while suppressing the intensity of the CDW. We investigate bulk properties and atomic scale scanning tunneling microscopy and spectroscopy in CuxTiSe2.STM measurements reveal coexistence of chiral charge density wave and superconductivity. We find that the amplitude of charge density wave modulationis strongly suppressed with respect to strongly underdoped case (x<0.06) with the chiral domain size remaining the same. Superconductivity exhibits BCS character at variety of dopings with indicating an intermediate coupling strength. Application ofthe external magnetic field introduces the Abrikosov vortex lattice that is weakly pinned. The size of the vortex core extracted from vortex images corresponds tothe one extracted from the upper critical field from magnetization measurements. Our results suggest that, if charge density wave quantum critical point exist, it should be well above the optimal copper concentration of x=0.08.

Biography of the Speaker:

Dr. Goran Karapetrov is Associate professor in Physics at Drexel University. He graduated from Moscow State University in 1991 and obtained his Ph.D. from Oregon State University in 1996. Prior to joining Drexel faculty in 2011, Dr. Karapetrov was a staff member at Materials Science Division at Argonne National Laboratory. He has a track record of accomplishments in the areas of scanning probe microscopy as related to strongly correlated electron systems and catalysis. Dr. Karapetrov’s scanning probe microscopy and bulk characterization laboratory includes facilities forsingle crystal growth. The unique combination of sample fabrication and nanoscale characterization provides unique research environment in which perfection of synthesis of new materials and discovery of new phenomena canthrive. Dr. Karapetrov has with more than 100 publications in international journals and several patent awards. He is an active member of APS and MRS organizing focus sessions at international conferences on magnetism and superconductivity.