Kavli Affiliate: Darrell G. Schlom
| First 5 Authors: Mohamed Nawwar, Mohamed Nawwar, , ,
| Summary:
This study reports the observation of phonon-drag thermopower polarity
reversal in Ba-doped KTaO3 thin films, mediated by electron-phonon Umklapp
scattering. Epitaxial films with distinct carrier concentrations (3.7 x 10^20
cm^-3 and 4.9 x 10^19 cm^-3) were grown via molecular-beam epitaxy. In heavily
doped samples, where the Fermi surface spans 80% of the Brillouin zone, the
Umklapp condition is satisfied, reversing electron momentum. This manifests as
a sign-reversal in the thermopower around 80 K upon cooling despite the sample
having only n-type carriers. On the other hand, the lightly doped sample (4.9 x
10^19 cm^-3) exhibits only a negative thermopower down to 2 K. These results
advance the understanding of Umklapp electron-phonon drag in oxides and
highlight KTaO3’s potential for engineering unconventional thermoelectric
materials.
| Search Query: ArXiv Query: search_query=au:”Darrell G. Schlom”&id_list=&start=0&max_results=3