Quantum criticality in quasi-one dimensional Li -0.9 Mo -6 O -17

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Quantum Criticality in Quasi-One Dimensional
Li0.9Mo6O17J.W. Allen, University of Michigan,
DMR 0302825(SRC, DMR-0084402)
For many indeed most physical systems there
are characteristic energy scales set by the
various forces that act. For example, the
ferromagnetism of iron disappears if the
temperature T is greater than 1043K (1418 F)
because thermal energy then exceeds the
characteristic energy of the magnetic forces in
iron. Quantum critical systems are strikingly
different in having no energy scale except
temperature itself. Quantum criticality (QC) is
predicted in theories of quasi-one dimensional
systems. QC may be important in nano-technology.
Studies of systems in nature are just
beginning. Here we use a technique called
photoemission spectroscopy to observe QC in the
spectra of the energy distribution of the
electrons of a quasi-one dimensional chemical
compound. The spectra have the QC scaling
property, that their shape depends only the ratio
of energy to temperature.
All data scaled
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Quantum Criticality in Quasi-One Dimensional
Li0.9Mo6O17J.W. Allen, University of Michigan,
DMR Award 0302825 (SRC, DMR-0084402)
Training for Multi-Institutional Research This
work is a good example of the multi-institutional
and internationally collaborative style of
research for which science students must now be
trained. The photoemission experiments are
performed by UM researchers at the NSF-funded
Wisconsin Synchrotron Radiation Laboratory using
samples prepared at the Oak Ridge National
Laboratory (David Mandrus group), and LEPES-CNRS,
Grenoble, France (C. Schlenker,J.
Dumas). Theoretical guidance has been provided
by S. Moukouri (UM) and José Alvarez, formerly a
UM postdoc, now returned to his native Spain, at
the University of Madrid.
Education This grant provides partial support
for two graduate students, Sung-Kwan Mo and
Feng Wang. Both have passed their Ph.D.
candidacy exams. The grant also supports summer
research opportunities for undergraduates like
Spencer Dowdall, a UM double major in physics and
math. Spencer has joined the experiments at the
Wisconsin SRC.