We are observing supercondutivity in semiconductors alloys of the type (CuInTe2)1-x(TaTe)x and (CuGaSe2)1-x(FeSe)x after freezing of magnetic clusters (reentrant spin-glass transition).
Insofar as I am aware, these materials, generally referred to as chalcopyrite-based diluted magnetic semiconductors (DMSs), are ferromagnets at room temperature. Ferromagnetism is pair-breaking for s-wave (singlet) superconductivity. This may clarify the reason for the entrance into superconductive state subsequent to glass transition, i.e. subsequent to destruction of long-range magnetic order. Perhaps you could present some details about what is known about the nature of superconductivity in these materials.
Thank you very much for your illustrative answer. In fact, up to now, there is not any report of superconductivity in these alloys. However, we are clearly observed that in two different sistems which have similar magnetic behavior. Our goal is to study magnetic properties of the general family (I-III-VI2)1-x(MT-VI)x alloys with MT=metal transition. In the literature, much of the experimental work has been done using MT=Mn which generally give antiferromagnetic ordering at low T or FM at room temperature. Following this reasearch line we used Fe, Co, Ta, Nb, V, Cr and Ni as MT. In the case of Fe and Ta we observed that magnetic properties can be explained by the formation of magnetic clusters but the transition to a superconductive state was unexpected. In the case of Nb, in the alloy (CuInTe2)1-x(NbTe)x with x=0.5 we observed a superconductive transition at 10K but a "normal" Curie-like behavior for T>10K. In the cases of Co, Cr, V or Ni we are not observed superconductor transitions.
You are welcome Pedro. Thank you for the details! As for anti-ferromagnetism at low temperatures, the situation is therefore similar to that of the undoped cuperates which are anti-ferromagnetic insulators. Anti-ferromagnetism disappears in these upon doping, however there is substantial anti-ferromagnetic fluctuations in the normal state of these compounds. These fluctuations are according to some theories (in particular the one by Pines, and collaborators -- Millis, Monien, Monthoux, Balatsky, etc.) responsible for the superconductivity pairing in these materials, taking over the role of the ionic fluctuations (i.e. phonons) in conventional superconductors. These fluctuations also account for quantum criticality (i.e. criticality at zero temperature) in the cuperates; the non-Fermi liquid behaviour of the normal metallic states of these compounds in particular in the underdoped region is believed to be due to quantum criticality. If interested, you may wish to consult the book Quantum Phase Transitions by Subir Sachdev (Cambridge University Press).
- Badges
- Science topic
- Similar topics
- Physical Sciences
- Materials Science
- Materials
- Inorganic Materials
- Metals
- Alloys