Atomically smooth high-Tc multilayers: a quest for extraordinary charge

 
Ivan Bozovic
Brookhaven National Laboratory, Upton NY 11973

 
Using the ‘next-generation’ molecular beam epitaxy system, we have reproducibly synthesized thin films of high-Tc superconductors (HTS) with surface roughness in the range 0.2-0.5 nm, much less than the unit cell height (1-2 nm) [1]. In these atomically smooth films one can observe some novel effects, such as spectacular interference patterns in resonant soft X-scattering. The latter provide a direct, bulk and instantaneous probe of inhomogeneity of the free-carrier fluid and of the superconducting condensate [2].

 Next, this technology has enabled fabrication of precise and uniform heterostructures, superlattices, and trilayer (sandwich) junctions, some of which contain barriers or HTS layers that are just one-unit-cell thick and yet have no pinholes over macroscopic area [3]. Apart from practical interest these devices allow one to probe some fundamental physics questions. Are spin and charge separated; do charge carriers bind in pairs or cluster in stripes? How far out of HTS can the superconducting order parameter leak ‑ and what is this telling us about the mechanism of HTS? Are the HTS and the anti-ferromagnetic insulator states nearly degenerate? The answers carry some surprises and provide strong constraints on the theory of HTS.

[1] I. Bozovic et al., Phys. Rev. Lett. 89, 107001 (2002).
[2] P. Abbamonte et al., Science 297, 581 (2002).
[3] I. Bozovic et al., Nature 421, 873 (2003).

Physics Colloquium
Date:  September 15, 2004 (Wednesday)

Abstract in PDF format