Recent experiments on decoherence rate in various mesoscopic systems [1] suggest a strong evidence for a non-thermal dissipation mechanism dominant at low temperatures. Keeping the anticipated consequences of such a mechanism in view, I first discuss the experiments in light of recent suggestions of mechanisms including two-level systems [2,3] or external high-frequency noise, to show that the observed trends cannot be reconciled with these suggestions. Then I discuss various aspects of the non-thermal low temperature decoherence [4,5]. In particular, the problem of the experimentally observed persistent current in normal metal rings is analyzed in the backdrop of a non-thermal decohering environment [6]. Prospects for a conceptual understanding of the size of the current, observed in experiments, along with the sign are explored.

References

[1] P. Mohanty, E.M. Jariwala, R.A. Webb, Phys. Rev. Lett. 78, 3366 (1997); Fortschr. der Physik 46, 779 (1998).
[2] Y. Imry, H. Fukuyama, and P. Schwab, preprint cond-mat/9903017, to be published in Europhys. Lett. (1999).
[3] A. Zawadowski, J. von Delft, D.C. Ralph, preprint cond-mat/9902176.
[4] R. Raimondi, P. Schwab, and C. Castellani, preprint cond-mat/9903146, to be published in Phys. Rev. B (1999).
[5] P. Mohanty, E. M. Q. Jariwala, M. B. Ketchen, and R. A. Webb, in Quantum Coherence and Decoherence, edited by K. Fujikawa, and Y. A. Ono (Elsevier Science, 1996).
[6] P. Mohanty, Annalen der Physik 8, 549 (1999).