SKM 2023 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 16: Poster: Transport
TT 16.3: Poster
Monday, March 27, 2023, 15:00–18:00, P2/OG4
Nonmonotonous Temperature Dependence of the Thermopower of Gold Atomic Contacts — Thomas Möller1, •Marcel Strohmeier1, Ruben Zerfaß1, Kim Nikolai Kirchberger1, Danial Majidi2, Juan Carlos Cuevas3, Johannes Boneberg1, Paul Leiderer1, Wolfgang Belzig1, and Elke Scheer1 — 1University of Konstanz, 78457 Konstanz, Germany — 2Université Grenoble Alpes, CNRS, Grenoble INP, Institut Néel, 38042 Grenoble, France — 3Universidad Autónoma de Madrid, E-28049 Madrid, Spain
We present measurements of the thermopower of atomic-size gold contacts realized by the mechanically controllable break junction (MCBJ) technique over a temperature range from 10 K to 295 K. While the conductance histograms confirm the quantum nature of the transport, we observe a non-monotonous temperature dependence of the ensemble-averaged thermopower (taking into account contacts between 1 and 20 G0 = 2e2/h) with a minimum of -2 µV/K at about 150 K. Our observations at low and high temperature are compatible with values reported in the literature [1-5], but the non-monotonous behavior in between disagrees with the expected linear increase of the thermopower for quantum coherent conductors described by the Landauer formula. We discuss several possible mechanisms, that may be at the origin of the deviation, such as phonon contributions or an energy-dependent transmission function. Both aspects can be addressed experimentally by analyzing current-voltage characteristics. We present here results obtained for Au and for Cu atomic contacts.