[1] Univ Calif San Diego, Dept Phys, La Jolla, CA 92093 USA
[2] Univ Calif San Diego, Ctr Theoret Biol Phys, La Jolla, CA 92093 USA
[3] Brandeis Univ, Dept Phys, Waltham, MA 02454 USA
[4] Rockefeller Univ, Ctr Studies Phys & Biol, New York, NY 10021 USA
[5] CALTECH, Dept Phys, Pasadena, CA 91125 USA
[6] Univ Munich, Dept Phys, Munich, Germany
[7] Univ Munich, CENS, Munich, Germany
[8] CALTECH, Div Engn & Appl Sci, Pasadena, CA 91125 USA
[9] CALTECH, Kavli Nanosci Inst, Pasadena, CA 91125 USA