Round 2: Tossup 15

In a cubic lattice, a BEC can undergo a phase transition between a superfluid and these materials when the ratio (10[1])of U to J exceeds 36. Symmetry classes denoted “A” correspond to a type of these materials in a so-called “periodic table” containing ten classes. (-5[1])These materials satisfy a criterion of “effective Bohr radius times the cube root of electron density” being less than about 0.2 to 0.4. Other materials may unexpectedly become these materials due to the (10[1])Peierls distortion. The Hubbard model correctly predicts the behavior of nickel oxides acting as these materials, as first proposed by Nevill Mott. (10[1])These materials lose (10[1])their behavior and begin to produce a current beyond the breakdown voltage. For 10 points, name these materials with a high band gap, thus making them poor conductors of electricity. ■END■ (10[1])

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