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HL: Fachverband Halbleiterphysik

HL 33: Poster II

HL 33.14: Poster

Wednesday, March 29, 2023, 17:00–19:00, P1

Towards thermoelectric transport measurements in dual-gated bilayer graphene — •Moritz Knaak, Martin Statz, and Thomas Weitz — 1st Physical Institute, Faculty of Physics, University of Göttingen, Friedrich-Hund-Platz 1, Göttingen 37077, Germany

The ratio of the thermal voltage to the corresponding temperature difference is defined as the Seebeck coefficient. As a transport coefficient due to its relation to the density of states (DoS) and its underlying link between entropy and charge transport, the Seebeck coefficient can help to better understand materials with interesting DoS and/or phase transitions. One of these materials is trigonally warped bilayer graphene (BLG), in which Lifshitz transitions can be induced by tuning an out-of plane electric field or the charge carrier density. Near these transitions the DoS is high and electron-electron interaction becomes important. To gain further insights into the emerging correlated phases near these Lifshitz transitions [1] and quamtify the changes in the DoS, we measure the thermoelectric voltage and local temperature difference to extract the Seebeck coefficient. For that we combine a hexagonal boron nitride encapsulated, dual-gated BLG device with graphite gates and contacts together with an on-chip heater next to the BLG. The source and drain contacts are simultaneously used as 4-point-probe on-chip resistance thermometers to determine the local temperature differences. The devices are fabricated utilizing the dry transfer method, e-beam lithography, thermal evaporation of contact leads as well as reactive ion etching.

[1] Seiler, A.M. et al. Nature 608, 298-302 (2022)