Superconductivity lower

We have remarked that a temperature of zero on the absolute temperature scale would correspond to the absence of all motion. The kinetic energy would become zero. Very interesting phenomena occur at temperatures near 0°K (the superconductivity of many metals and the superfluidity of liquid helium are two examples). Hence, scientists are extremely interested in methods of reaching temperatures as close to absolute zero as possible. Two low temperature coolants commonly used are liquid hydrogen (which boils at 20°K) and liquid helium (which boils at 4°K). Helium, under reduced pressure, boils at even lower temperatures and provides a means of reaching temperatures near 1°K. More exotic techniques have been developed to produce still lower temperatures (as low as 0.001°K) but even thermometry becomes a severe problem at such temperatures. 

In 1908, Kamerling-Onnes got the liquefaction of helium (discovered by Janssen e Lockyer during the solar eclipse of 18 August 1868). Kamerlingh-Onnes obtained in Leiden 60 cc of liquid helium extracted from several tons of monazite sable imported from India. Kamerlingh-Onnes himself discovered the X-transition and the superfluidity in 4He and in 1911 the superconductivity of Hg, a particularly pure substance at that time. In the race towards lower and lower temperatures, Kamerling-Onnes, pumping on liquid 4He, obtained 0.7K in 1926. 

For large enough asymmetries the homogeneous state becomes unstable towards formation of either the LOFF phase - a superconducting state with nonzero center-of-mass momentum of the Cooper pairs, or the DFS phase - a superconducting state which requires a quadrapole deformation of Fermi surfaces. A combined treatment of these phases in non-relativistic systems shows that while the LOFF phase corresponds to a local minimum, the DFS phase has energy lower that the LOFF phase. These phases break either the rotational, the translational or both symmetries. 

As a first step in this direction we will discuss here the two flavor color superconducting (2SC) quark matter phase which occurs at lower baryon densities than the color-flavor-locking (CFL) one, see [18, 32], Studies of three-flavor quark models have revealed a very rich phase structure (see [32] and references therein). However, for applications to compact stars the omission of the strange quark flavor within the class of nonlocal chiral quark models considered here may be justified by the fact that central chemical potentials in stable star configurations do barely reach the threshold value at which the mass gap for strange quarks breaks down and they appear in the system [20], Therefore we will not discuss here first applications to calculate compact star configurations with color superconducting quark matter phases that have employed non-dynamical quark models... 

We have investigated the influence of diquark condensation on the thermodynamics of quark matter under the conditions of /5-equilibrium and charge neutrality relevant for the discussion of compact stars. The EoS has been derived for a nonlocal chiral quark model in the mean field approximation, and the influence of different form-factors of the nonlocal, separable interaction (Gaussian, Lorentzian, NJL) has been studied. The model parameters are chosen such that the same set of hadronic vacuum observable is described. We have shown that the critical temperatures and chemical potentials for the onset of the chiral and the superconducting phase transition are the lower the smoother the momentum dependence of the interaction form-factor is. 

The phase transition to color superconducting quark matter from the lower density regions at small temperatures (T < 5 a 10 MeV) is of first order, while the melting of the diquark condensate and the corresponding transition to normal quark matter at high temperatures is of second order. The presence... 

We talked for more than an hour about these ideas and what finally emerged was the need for a test, or at least Dennis maintained that a partial test of the idea could be undertaken to convince me and our companions. He thought that as the superconducting state became stabilized there should be a marked lowering of temperature in the immediate area. In our talking, he and I had left the area of the hut and drifted down the forest path. It would be possible to attempt to generate the effect of coolness right there on the spot, he supposed. 

Superconductivity is absent in li CgQ, Na CgQ and C q based fullerides. Band stmeture calculations for predict the Fermi-level to be close to the lower... 

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