By exploration of smaller and still smaller length scales, much has been learned about the fundamental interactions in nature. At the other extreme, condensed matter physicists have studied the collective statistical behavior of large numbers of particles. In a merging of these two approaches, intermediate size systems with relatively small numbers of atoms have recently been fabricated and studied. Novel effects have been discovered in these so-called mesoscopic systems. Traditionally these are samples of extremely small volume. But model systems with enlarged "atoms", such as vortices in superconducting networks may suffice. Recent advances in the understanding of disordered systems, critical phenomena, and non-linear dynamics have also made it irresistible to ask deeper questions about complexity. Professor Israeloff's approach is to probe model complex systems with novel mesoscopic techniques. In this way important phenomena which are averaged away in large samples can now be probed.

Current experiments include: mesoscopic studies of superconducting, disordered, and biological materials. With several techniques the detailed dynamics of vortices in superconductors and superconducting arrays are now being probed. The vortices are localized regions of magnetic field penetration around which circulate super-currents. These vortices must be pinned or nailed down, else they dissipate energy destroying the superconductivity. Also of interest are exotic transitions between the various fluid, crystalline, and glassy vortex phases which have recently been discovered. Understanding strong driven motion of vortices may shed some light on other complex problems, such as friction, granular flow, invasion, and charge transport. Vortex motion is being studied in ultra small high-temperature and conventional superconductors, arrays, and Josephson junctions. Mesoscopic high sensitivity magnetic field sensing arrays (Hall effect), and transport measurements are being utilized.

Under development is a low-temperature magnetic field imaging system which will make possible real-time study of magnetic flux invasion and pattern development in superconductors.

• "Numerical Study of Aging in Coupled Two-Level System", T. S. Grigera and N. E. Israeloff, Philosophical Mag. B 82, 313 (2002)
• "Observation of Fluctuation-Dissipation-Theorem Violations in a Structural Glass", Tomas S. Grigera and N. E. Israeloff, Phys. Rev. Lett. 83, 5083 (1999)
• "Observation of Fluctuation-Dissipation-Theorem Violations in a Structural Glass," Tomas S. Grigera and N. E. Israeloff. Physical Review Letters, Volume 83, No. 24 (December 13, 1999).
• "Low-frequency dielectric fluctuations near the glass transition.", T. S. Grigera, N.E. Israeloff, Europhysics letters. AUG 01 1998 v 43 n 3
• "Field-enhanced superconductivity in disordered wire networks." N.E. Israeloff, C. Bonetto and R. Bojko, Physical review b: condensed matter. JUL 01 1998 v 58 n 1.
• "Mesoscopic-scale dielectric relaxation at the glass transition." L.E. Walther, N.E. Israeloff, and H. Alvarez Gomariz, Physical review b: condensed matter. JUN 15 1998 v 57 n 24