Cooper-pair and Bose-Einstein condensations in two dimensions: A critical analysis based on the Nozieres and Schmitt-Rink formalism
- Department of Physics, Nagoya University, Nagoya 464-01 (Japan)
- Department of Physics, College of General Education, Nagoya University, Nagoya 464-01 (Japan)
The crossover between the Cooper-pair condensation and the Bose-Einstein condensation of di-electronic'' molecules in two-dimensional superconductors is investigated in detail on the basis of the Nozieres and Schmitt-Rink formalism. It is shown that temperature dependence of the chemical potential [mu] so calculated is classified into two classes as decreasing temperatures; i.e., class (a) where [mu] approaches the point of Bose-Einstein condensation of two-dimensional ideal Bose gas of di-electronic'' molecules, and class (b) where [mu] diverges positively along the line of BCS-type mean-field pair condensation. This feature is rather universal irrespective of strength [ital V] of the attractive interaction of the [ital s]-wave type. While the former class (a) has been found by Schmitt-Rink, Varma, and Ruckenstein, existence of the latter class (b) is recognized here. In the case where [ital V] is fixed, class (a) is realized for electron number density [ital N] smaller than [ital N][sub cr], which is an increasing function of [ital V], and class (b) is realized for [ital N] larger than [ital N][sub cr]. If [ital N][much gt][ital N][sub cr] in particular, there exists a regime, where the Fermi-liquid-like description is valid, between the BCS-type mean-field transition temperature and the Fermi temperature. In the situation where [ital V] is changed with [ital N] being fixed, low-temperature states for the strong-coupling case belong to class (a) while those for the weak-coupling case belong to class (b). Therefore, with decreasing [ital V], the chemical potential [mu]([ital T]), at temperatures far below the Fermi temperature, shows a discontinuous jump at [ital V]=[ital V][sub cr]([ital N]) corresponding to the transition from class (a) to (b).
- OSTI ID:
- 6642002
- Journal Information:
- Physical Review, B: Condensed Matter; (United States), Vol. 47:18; ISSN 0163-1829
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
SUPERCONDUCTIVITY AND SUPERFLUIDITY
SUPERCONDUCTIVITY
TWO-DIMENSIONAL CALCULATIONS
BCS THEORY
BOSE-EINSTEIN CONDENSATION
COOPER PAIRS
MEAN-FIELD THEORY
TEMPERATURE EFFECTS
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
PHYSICAL PROPERTIES
665411* - Basic Superconductivity Studies- (1992-)