Josephson array of mesoscopic objects. Modulation of system properties through the chemical potential |
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Authors: | A I Belousov S A Berzakov Yu E Lozovik |
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Institution: | (1) Institute of Spectroscopy, Russian Academy of Sciences, 142092 Troitsk, Moscow Region, Moscow |
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Abstract: | The phase diagram of a two-dimensional Josephson array of mesoscopic objects (superconducting granules, superfluid helium
in a porous medium, traps with Bose-condensed atoms, etc.) is examined. Quantum fluctuations in both the modulus and phase
of the superconducting order parameter are taken into account within a lattice boson Hubbard model. Modulating the average
occupation number n
0 of the sites in the system (the “number of Cooper pairs” per granule, the number of atoms in a trap, etc.) leads to changes
in the state of the array, and the character of these changes depends significantly on the region of the phase diagram being
examined. In the region where there are large quantum fluctuations in the phase of the superconducting order parameter, variation
of the chemical potential causes oscillations with alternating superconducting (superfluid) and normal states of the array.
On the other hand, in the region where the bosons interact weakly, the properties of the system depend monotonically on n
0. Lowering the temperature and increasing the particle interaction force lead to a reduction in the width of the region of
variation in n
0 within which the system properties depend weakly on the average occupation number. The phase diagram of the array is obtained
by mapping this quantum system onto a classical two-dimensional XY model with a renormalized Josephson coupling constant and is consistent with our quantum path-integral Monte Carlo calculations.
Zh. éksp. Teor. Fiz. 114, 591–604 (August 1998) |
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Keywords: | |
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