Doping dependent transport in YBCO nanostructures: insights into the microscopic mechanism for high critical temperature superconductivity
Typ
Examensarbete för masterexamen
Program
Publicerad
2020
Författare
Toskovic, Ranko
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
The microscopic mechanism responsible for superconductivity in high critical temperature
superconductors (HTSs), almost three decades after their discovery, still remains unknown. It is
widely believed that studies in the underdoped (UD) regime of these materials could shed light
on this unresolved question.
In this thesis project, a controllable and reproducible Pulsed Laser Deposition (PLD)
growth of underdoped YBa2Cu3O7-δ (YBCO) films was done by changing only the postannealing
pressure. X ray diffractometry (XRD) scans of the films have shown a
continuous YBCO unit cell expansion as the pressure decreased, indicating a reduction in the
doping level of our films. Rather sharp resistance vs. temperature transitions obtained in our
films indicate a high level of homogeneity. First steps towards optimization of the surface
properties of the films have been also undertaken.
A soft-patterning technique developed previously in our group, preserving homogeneity
of submicron structures, was employed for nanorings’ patterning on the optimally doped films.
Little Parks (LP) experiments were conducted on rings with different sizes. Cooper pairs have
been identified as the predominant charge carriers in all the rings, as expected at the optimal
doping level.
Beskrivning
Ämne/nyckelord
high critical temperature superconductivity, YBCO, Little Parks effect, underdoped and optimally doped films, nanorings