Lecturer: Prof. Aviad Frydman
Affiliation: Department of Physics,
Bar-Ilan University
Abstract:
The superconductor-insulator transition
(SIT) is regarded as a prototype of a
quantum phase transition. Varying a non-
thermal tuning parameter, such as disorder,
causes the system to switch from a perfect
conductor to a perfect insulator. Despite the
long history of research in the field, the
nature of the SIT and especially that of the
insulating phase is still very much under
debate and the full understanding awaits
new and innovation methods.
A quantum phase transition is governed by
quantum rather than thermal fluctuations.
For the SIT these are manifested by
collective order-parameter amplitude and
phase modes (known as Higgs and
Goldstone modes) that are predicted to
become prominent in the vicinity of the
quantum phase transition. In my talk I will
describe two new experiments on systems
close to the SIT. The first is a study of the
ac conductivity in thin disordered
superconducting films close to the SIT using
terahertz spectroscopy. The second is a
measurement of specific heat of thin
granular superconductors through the SIT.
Both experiments show excess electronic
spectra or degrees of freedom which are
identified as collective modes close to the
quantum phase transition.