Special CPM Seminar

maging coherent thermoelectric transport through quantum devices

Boris Brun-Barrière

UC Louvain

In the global context of arising quantum technology as well as increasing care for energy harvesting, thermoelectric transport has recently regained interest. We developed a new scanning probe technique to image thermoelectric transport in two-dimensional devices: Scanning Gate Thermoelectric Microscopy (SGTM). This technique is derived from Scanning Gate Microscopy (SGM), that consists in mapping changes in a device's electrical conductance induced by a moving electrostatic perturbation, generated with a biased AFM tip [1-3]. SGTM consists in recording the devices' Seebeck coefficient instead of its electrical conductance. To achieve this measurement, we heat one side of the device and record the thermoelectric voltage arising across the device in response to this temperature difference. We then scan the electrically biased tip above the surface while recording this signal (fig.1b and fig.1d). Surprisingly, SGTM unveils much greater details than SGM, making it very promising to study the thermoelectric properties of various quantum electronic devices at the local scale.

Fig.1: a,b) SGM and SGTM images in the vicinity of a GaAs/AlGaAs quantum point contact, exhibiting nterference fringes spaced by λ_F/2. c,d) SGM and SGTM images on a InAlAs/InGaAs network. SGTM higlights ingle electron charging events, appearing as concentric rings around a local charge trap.

References:
[1] M.A Topinka et al., Nature 2001, 416, 183-186
[2] B. Hackens et al., Nat. Com 2010, 1, 39
[3] B. Brun et al., Nat. Com. 2014, 5, 4290