Dresden 2009 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 19: Correlated Electrons: Metal-Insulator Transition 3
TT 19.4: Vortrag
Dienstag, 24. März 2009, 14:45–15:00, HSZ 301
Pressure-induced superconductivity in the Mott insulator GaNb4S8 — Xin Wang1, •Martin K. Forthaus2, Karl Syassen1, Mathias Kraken3, Jochen Litterst3, Hubertus Luetkens4, Dirk Johrendt5, and Mohsen M. Abd-Elmeguid2 — 1Max-Planck-Institut für Festkörperforschung, Stuttgart, Germnay — 2II. Physikalisches Institut, Iniversität zu Köln, Köln, Germany — 3Institut für Physik der kondensierten Materie, TU Braunschweig, Braunschweig, Germany — 4Paul Scherrer Institut, Villigen, Switzerland — 5Department Chemie und Biochemie, LMU München, München, Germany
GaNb4S8 (cubic fcc GaMo4S8 type structure) belongs to a new class of Mott insulators in which the electronic conduction originates from hopping of localized electrons (S=1/2) among widely separated tetrahedral Nb4 metal clusters. The magnetic susceptibility (χ(T)) of GaNb4S8 shows Curie-Weiss behavior (100≤ T≤300 K) and reveals a sudden drop around 30 K but no long range magnetic order has been detected down to 1.6 K. Recent strutural investigation shows that the drop of χ(T) is associated with a tetragonal distortion. We find pressure-induced superconductivity in GaNb4S8 with TC=2.1 K at p=10 GPa which increases with pressure up to 4 K at 23 GPa. As our µSR experiments at ambient pressure clearly shows that the tetragonal distortion in GaNb4S8 is associated with the onset of short range magnetic order, we discuss the possibility of a nonconventional pressure-induced superconducting state.