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V2O3 is the prototype system for the Mott
transition, one of the most fundamental phenomena
of electronic correlation. Here, temperature,
doping or pressure induce a metal to insulator
transition (MIT) between a paramagnetic metal and
a paramagnetic insulator. This or related MITs
have a high technological potential, among others
for intelligent windows and field effect transistors. As this MIT was well studied
experimentally [1] and theoretically even by
realistic local density approximation plus
dynamical mean field theory calculations [2]
before, it was a big surprise that our new
experimental and theoretical results
[3-5] put a new twist to the V2O3 story.
First, a microscopic photoemission view revealed
that the metallic state of slightly doped V2O3 is actually a percolation of metallic and insulating islands, where upon increasing
temperature the metallic islands turn insulating
at the MIT [3]. Second, the long-hold paradigm
of the equivalence of doping and pressure for the
MIT does not bear a closer experimental and
theoretical inspection. While doping increases
the crystal field splitting between a1g and
egpi states, decreasing pressure reduces the
bandwidth. That is, exactly the two
opposite parameters which control the multi-
orbital MIT are affected.
Third, infrared conductivity showed the
disappearance of quasiparticle excitations and
the opening of a pseudogap with increasing
temperature [5].
[1] D. B. McWhan et al., Phys. Rev. B 7, 1920 (1973). [2] K. Held et al., Phys. Rev. Lett. 86 5345 (2001). [3] S. Lupi et al., Nature Communications 1, 105 (2010). [4] F. Rodolakis et al., Phys. Rev. Lett. 104, 047401 (2010). [5] L. Baldassarre et al., Phys. Rev. B 77, 113107 (2008). |
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