Berlin 2008 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 36: Superconductivity: Properties, Electronic Structure, Order Parameter
TT 36.4: Talk
Friday, February 29, 2008, 11:00–11:15, H 0104
High-pressure study of layered bulk phases of elemental boron — •Jens Kunstmann1, Lilia Boeri1, and Jens Kortus2 — 1Max-Planck-Institut für Festkörperforschung, Heisenbergstr. 1, 70569 Stuttgart, Germany — 2Inst. für Theoretische Physik, TU Bergakademie Freiberg, Leipziger Str. 23, 09596 Freiberg, Germany
The valence shell of boron contains less electrons than available orbitals, which results in very complex bulk structures, primarily consisting of B12 icosahedra. But boron is relatively little studied and many properties such as the phase diagram, the ground state structure, and its high-pressure behavior are unknown. Recently two discoveries put elemental boron into the scientific focus. One is that it becomes superconducting under high pressure. The other one is that small clusters form two-dimensional sheet-like structures, as suggested by theoretical studies of Boustani and Quandt in the mid-1990s. The high-pressure superconductivity is not fully understood so far, because the corresponding crystal structures are still under debate. Hence before solving the problem of understanding the coupling mechanism for superconductivity one has to solve first the problem of determining the crystal structure. The existence of sheet-like clusters poses the question if boron sheets, similar to graphene, or layered bulk phases, similar to graphite, may also exist for boron. Therefore our study tries to approach the following questions: What do such layered bulk structures look like? What are their stabilities in comparison with other bulk phases? Are they dynamically stable and if yes, are they responsible for the high-pressure superconductivity of elemental boron?