טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentLubashevsky Yuval
SubjectStudies of the Supercoducting Gap in Zn Substituted Cuprates
DepartmentDepartment of Physics
Supervisor Professor Amit Kanigel
Full Thesis textFull thesis text - English Version


Abstract

The relation between the pseudo-gap (PG) and superconductivity (SC) in the high-temperature superconducting cuprates (HTSC) remains a matter of controversy. In fact, many believe that therein lies the key to understanding the cuprates’ physics. During years a large body of experimental data was gathered but the results are inconclusive. While there is support for the concept of the PG being a state in which Cooper pairs are pre-formed, there are also numerous experiments providing evidence for a competing order. A simple, but potentially very powerful, approach would be to look for correlations between measurable quantities and the two obvious energy scales that govern the cuprate phase diagram: Tc and T*. This approach is complicated by the fact that the parameter which sample growers control, the doping level, affects both Tc and T* simultaneously. Here we overcome this problem using Zinc (Zn) substitution. Zn substitution allows us to manipulate Tc and T* separately. We measure and compare the superconducting gaps of different samples, in that way we can observe directly the correlation between Tc, T* and the most basic property of a superconductor, The energy gap. We show that Tc is not related to the gap shape or size, but it controls the size of the coherence peak at the gap edge.