Universal conductivity at the superconductor-insulator transition in thin films

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1992

OSTI ID:6971655

Cha, M C

Recent experimental attention has focused on the onset of superconductivity in thin two-dimensional films at zero temperature. By systematically varying control parameters, it has been possible to tune through a (T=0) superconductor-insulator transition. One of the most interesting properties in this phenomenon is that the value of the sheet resistance at the boundary between the superconducting and insulating states at very low temperature seems to be universal, independent of the microscopic details of the sample. Furthermore, this number appears to be close to R[sub Q] [triple bond] h/(2e)[sup 2] [approximately] 6.45k[Omega], the quantum resistance for Cooper pairs. The authors argue that the relevant degrees of freedom at the transition are bosonic and an interacting boson model, called the boson Hubbard model, is studied to understand issues related with superconductor-insulator transition. Also scaling theories have predicted that the conductivity at the superconductor-insulator transition is a universal number. To test the new notion of universal conductivity, they calculate the conductivity at the superconductor-insulator transition in a pure boson Hubbard model at integer filling. In this model, the transition occurs between superfluid phase and Mott insulating phase with a commensurate density. The authors obtain consistent results for the universal conductivity by a large-N expansion method and by Monte Carlo simulation. Even though the universality class of this model is expected to be different from experimental situations, calculations support the notion of the universal conductivity and give an estimate of its value which will be useful for further experimental and theoretical studies.

• Research Organization: Indiana Univ., Bloomington, IN (United States)
• OSTI ID: 6971655
• Country of Publication: United States
• Language: English

Related Subjects

665411* -- Basic Superconductivity Studies-- (1992-)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
CRYSTAL MODELS
ELECTRIC CONDUCTIVITY
ELECTRICAL EQUIPMENT
ELECTRICAL INSULATORS
ELECTRICAL PROPERTIES
EQUIPMENT
FILMS
HUBBARD MODEL
INTERACTING BOSON MODEL
MATHEMATICAL MODELS
NUCLEAR MODELS
PHYSICAL PROPERTIES
SHELL MODELS
SUPERCONDUCTIVITY
THIN FILMS