Issue |
Europhys. Lett.
Volume 58, Number 2, April 2002
|
|
---|---|---|
Page(s) | 278 - 284 | |
Section | Condensed matter: electronic structure, electrical, magnetic, and optical properties | |
DOI | https://doi.org/10.1209/epl/i2002-00634-2 | |
Published online | 01 August 2002 |
The amplification of the superconducting
by
combined effect of tuning of the Fermi level and the
tensile micro-strain in
x
2
1
Dipartimento di Fisica and Unità INFM,
Università di Roma “La Sapienza”
P. le Aldo Moro 2, 00185 Roma, Italy
2
Istituto di Strutturistica chimica del CNR, Area Ricerca di
Roma Montelibretti 00016
Monterotondo Stazione, Italy
3
Dipartimento di Chimica, Università di Roma “La
Sapienza” P. le Aldo Moro 2, 00185 Roma, Italy
4
Dipartimento di Fisica, Università dell'Aquila
and Unità INFM - L'Aquila, Italy
5
Dipartimento di Chimica e Chimica Industriale,
Universtità di Genova Via Dodecaneso 31, 16146 Genova, Italy
6
Dipartimento di Fisica, Università di Cagliari
and Unità INFM - Cagliari, Italy
7
Unità INFM & Dipartimento di Fisica, Università
di Roma Tre Via della Vasca Navale 84, 00146 Roma, Italy
Received:
18
June
2001
Accepted:
23
January
2002
The increase of with x in
x
2 is controlled by the
Fermi level tuning at a “shape resonance”
(i.e., the 2D-3D cross-over, at x=0.66, of the topology
of the Fermi surface of σ holes in the superlattice of
boron mono-layers intercalated by
x
ions) and by the tensile “micro-strain” in the boron
sub-lattice (due to the lattice misfit between the boron and the
intercalated layers). The softening of the
phonon
frequency with increasing boron tensile micro-strain ε
in the range
shows the increasing
electron-lattice interaction. The linear scaling, for 0.66<x<1,
of
vs. the Fermi temperature
of the σ holes shows a constant coupling strength with
(where
is the Fermi wave vector
and
is the Pippard coherence length) that points toward a
vibronic pairing mechanism.
PACS: 74.62.-c – Transition temperature variations / 74.25.Dw – Superconductivity phase diagrams / 74.25.Jb – Electronic structure
© EDP Sciences, 2002
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