Superconducting cuprates and magnetoresistive manganites: similarities and contrasts
Introduction
Since the end of 1986, when high temperature superconductors came into being, the subject has captured the interest of one of the largest segment of the research community in any sub-field of Physics [1], [2], [3], [4], [5]. Despite the level and pace of the research, the origin of the nature of transport in the cuprates is still known piece meal and the microscopic mechanism of the pairing process still eludes us [6], [7], [8], [9]. Even the normal state transport properties continue to challenge our understanding and truly innovative experiments are needed to get at the root of these issues [10], [11], [12]. Over the last 5 years or so the condensed matter community has been pursuing yet another family of perovskites, the colossal magnetoresistive manganites, with a degree of intensity second only to the high Tc cuprates [13], [14]. This is simply because the underlying physics behind the observed phenomena, encompass some of the most exciting ideas in condensed matter Physics involving highly correlated electronic systems with strong electron–phonon coupling and magnetic interactions [15], [16], [17], [18]. In addition, familiar ideas in solid state chemistry involving electronic orbitals and bond hybridization have been readily adopted in this field [19], [20]. The manganite system may be an enabler in furthering our understanding of the cuprates. In this system, the strong electron–phonon interaction results in a precisely and relatively easily measurable correlation of transport properties with lattice distortions from which lessons may be drawn regarding similar effects in the case of the cuprates. The more visible role of electron spins on the transport properties of the manganites may shed light on the role of antiferromagnetic order in the Cooper pairing mechanism in the cuprates. In this paper we present three different experiments involving both the cuprates and the manganites, which we believe are very important for furthering our understanding of these rather enigmatic materials systems.
Section snippets
Ion channeling study of ion dynamics
Let us consider some of the important similarities between the cuprates and the manganites. In the less conducting state of the materials the electrical transport can be understood as due to charge hopping between adjacent Cu or Mn sites. The hopping frequencies increase as the conductivity of the material increases and this has effects on the dynamic lattice distortions whose frequencies are comparable with phonon frequencies. Thus the lattice distortions would no longer follow the charge
Optical excitation study of electron dynamics
We can learn significant information about the material systems by studying their electron dynamics. In retrospect the previous section dealt with dynamics of the ions measured by a technique which takes snap shots of the nuclei at very short time intervals (∼10−20 s determined by the ion scattering times)
Spin-polarized quasi-particle injection into high temperature superconductors
In the last set of experiments, we have coupled the HTS and CMR together to study the effect of spin-polarized electrons on the superconductor. All the efforts in this direction to date [51], [52], [53] consist of FET structures in which the critical current of the HTS channel is modulated by spin-polarized current injected from a CMR gate electrode. This modulation is compared with the gate electrode replaced by a non-ferromagnetic electrode such as Lanthanum nickel oxide, which is
Summary
These three sets of experiments, which probe ion, electron and spin dynamics, need to be refined further, though even at this stage the data produced by these experiments clearly point to exciting ways for us to unravel the mystery of these materials. The rejuvenation of research in the manganite is certainly having a synergistic effect on the cuprate research.
Acknowledgements
The authors would like to acknowledge ONR Grant No. ONR-N000149611026 (Program Monitor: Deborah Van Vechten) and NSF MRSEC Grant No. DMR96-32521. T. Venkatesan would like to thank the Institute of Mathematical Sciences, Chennai (Madras), India for their hospitality, during a portion of this work.
References (54)
- et al.
Z. Phys.
(1986) - Proceedings of the 19th International conference on low temperature physics, Physica B, 165–166...
- Proceedings of the International conference on Materials and Mechanisms of Superconductivity, M. Tachiki, Y. Muto, Y....
- Proceedings of the 1996 Applied Superconductivity Conference, IEEE Trans. Appl. Supercond., Vol. 7...
- Proceedings of the 21st International Conference on Low Temperature Physics, Czechoslov. J. Phys. 4 Suppl....
- et al.
J. Phys. Chem. Solids
(1995) J. Phys. Chem. Solids
(1995)- et al.
Phys. Rev.
(1994) - et al.
Phys. Rev. Lett.
(1993) Science
(1987)
Phys. Rev. Lett.
Phys. Rev. Lett.
Phys. Rev. Lett.
J. Phys. Soc. Jpn.
J. Phys. Soc. Jpn.
J. Phys. Soc. Jpn.
Phys. Rev.
J. Solid. State. Chem.
Introduction to Solid State Physics
Appl. Phys. Lett.
Appl. Phys. Lett.
Solid State Comm.
Phys. Rev.
Phys. Rev. Lett.
Materials Analysis by Ion Channeling
Cited by (2)
Low field magnetotransport in manganites
2008, Journal of Physics Condensed MatterColossal-magnetoresistive manganite thin films
2001, Journal of Physics Condensed Matter