Xinsheng Sean Ling
Professor of Physics:
Physics
Phone: +1 401 863 2582
xsling@brown.edu
Biography
B.S. 1984, Wuhan University; M.S. 1987, Chinese Academy of Sciences; Ph.D. 1992, the University of Connecticut. Postdoc 1992-1994, Yale University; Visiting Scientist 1994-1996, NEC Research Institute at Princeton. Assistant Professor (1996-2002), Associate Professor (2002-2008), Professor of Physics (2008-), Brown University. Visiting Professor 2002-2003(on sabbatical from Brown), Delft University of Technology (The Netherlands). Research Innovation Award (1998), the Research Corporation; Alfred P. Sloan Fellow (1998); Guggenheim Fellow (2002); APS Fellow (2005).
Interests
Single-Molecule Biophysics with Solid-State Nanopores and Nanochannels
This is an emerging frontier of condensed matter physics. The technological challenge is to develop a DNA sequencing technology that will be faster but with lower cost than that of Sanger method.
Neutron Scattering and Vortex Physics:
Ever since the seminal papers of A.I. Larkin, and Y. Imry and S.k. Ma, in 1970s, whether long-range order of any kind can exist in systems with random pinning has been one of the most important problems in condensed matter physics. Simple scaling arguments of Imry-Ma would suggest that random pinning of any strength will destroy long-range order below four dimensions in systems with a continuous order parameter, e.g. the Abrikosov vortex line lattice in type-II superconductors. However, renewed theoretical interests in the random pinning problem in the 1990s have led to profoundly new insight that topological order (i.e. orientation) can survive in weak random pinning systems even though the translational long-range order cannot exist. The resulting phase has the unusual property that the elastic lattice has power-law Bragg peaks, in contrast to the delta-function Bragg peaks for conventional crystalline order. This new pinned topological phase has been called the Bragg Glass.
The first implication of the Bragg glass model is that with increasing temperature or random pinning strength, the Bragg glass will become disordered in a true phase transition. Such a genuine order-disorder transition has now been well established using neutron diffraction, first in 2001 by our team using the NIST-NCNR facility. The recent improvements in neutron scattering facilities have provided unprecedented opportunities for vortex physics since neutrons are the only structure probes that can be used to directly measure the structural information of the vortex matter. Our ongoing DOE-funded effort is focused on the formation and nature of long-range-order of vortex line lattice in bulk Nb with random pinning.
At the top of our research agenda is to carry out a high-resolution (in q) measurement of the Bragg glass structure factor which is predicted to have a characteristic power-law form, similar to that of a 2D solid with thermal fluctuations but without random pinning.
Colloidal Matter: phase transitions and statistical mechanics
Awards
Fellow, American Physical Society (2005)
Guggenheim Fellow (2002)
Alfred P. Sloan Fellow (1998)
Research Innovation Awards, Research Corporation (1998)
Affiliations
American Physical Society (Fellow, Life Member)
Teaching
I teach both undergraduate and graduate level courses.
Funded Research
NIH National Human Genome Research Institute: R21 "Hybridization-Assisted Nanopore DNA Sequencing" (Aug.1, 2007-July 31, 2010), $820,000.
DOE Basic Energy Sciences:"Neutron scattering studies of vortex matter" (Aug.15, 2007-July 31, 2010), $600,685.
National Science Foundation Grant, "NIRT: DNA Sequencing and Translocation Studies using Electrically-Addressable Nanopore Arrays", (07/04-06/08) $1,550,000 (Brown $900,000, Harvard $650,000) (PI: Ling (Brown), Co-PIs: A. Meller (Harvard), D.R. Nelson (Harvard), and J. Oliver (Brown)).
National Science Foundation Grant, DMR: "Investigation of Vortex Matter Phase Transitions in Type-II Superconductors using Small Angle Neutron Scattering and Complementary Techniques", (07/04-06/07), $330,000.
National Science Foundation Grant, "NER: DNA Sequence Detection using Novel Solid-State and Soft Nanopores", (09/03-08/04), $100,000.
National Science Foundation Grant, MRI: "Acquisition of a Scanning Probe Microscope for Studies of Biomolecules and Nanoscale Materials and Devices", (07/03-06/04), $133,000 (PI: J. Tang, co-PIs: Ling, Valles and Xiao).
Salomon Faculty Research Award for research in nanopore biophysics (02-03).
National Science Foundation Grant, MRI: "Acquisition of a Workhorse Electron Beam Lithography System for Microstructured Materials and Devices Research", (07/01-06/02), $151,200.
National Science Foundation Grant, DMR: "Novel Studies of Vortex Matter and Peak Effect using In-Situ Neutron Scattering and AC Magnetization", (07/01-06/04), $277,000.
National Science Foundation Grant, SGER: "In-Situ Measurements of Small Angle Neutron Scattering and AC Magnetic Susceptibility of Vortex Matter", (07/00-06/01), $59,949.
Salomon Faculty Research Award for research in vortex matter (00-01).
National Science Foundation Grant, DMR: "Novel Studies of Two-Dimensional Colloidal Crystals in Pinning Potentials", (07/98-06/02), $240,000.
Petroleum Research Fund Grant, "Novel Studies of Two-Dimensional Colloidal Crystals in Pinning Potentials", (07/98-06/99), $35,000.
Salomon Faculty Research Award for research in 2D colloidal crystals (98-99).
Research Corporation, "Experimental Studies of Topological Defects and Order in 2D Colloidal Crystals", (07/98-06/00), $35,000.
Alfred P. Sloan Fellowship, (1998) $35,000.
Web Links
Curriculum Vitae
Download Xinsheng Sean Ling's Curriculum Vitae in PDF Format
