Details

Autor(en) / Beteiligte

• Wang, Jinhua
• Nie, Pan
• Li, Xiaokang
• Zuo, Huakun
• Fauqué, Benoît
• Zhu, Zengwei
• Behnia, Kamran

Titel

Critical point for Bose–Einstein condensation of excitons in graphite

Ist Teil von

• Proceedings of the National Academy of Sciences - PNAS, 2020-12, Vol.117 (48), p.30215-30219

Ort / Verlag

United States: National Academy of Sciences

Erscheinungsjahr

2020

Quelle

EZB Electronic Journals Library

Beschreibungen/Notizen

• An exciton is an electron–hole pair bound by attractive Coulomb interaction. Short-lived excitons have been detected by a variety of experimental probes in numerous contexts. An excitonic insulator, a collective state of such excitons, has been more elusive. Here, thanks to Nernst measurements in pulsed magnetic fields, we show that in graphite there is a critical temperature (T = 9.2 K) and a critical magnetic field (B = 47 T) for Bose–Einstein condensation of excitons. At this critical field, hole and electron Landau subbands simultaneously cross the Fermi level and allow exciton formation. By quantifying the effective mass and the spatial separation of the excitons in the basal plane, we show that the degeneracy temperature of the excitonic fluid corresponds to this critical temperature. This identification would explain why the field-induced transition observed in graphite is not a universal feature of three-dimensional electron systems pushed beyond the quantum limit.