You are cordially invited to the SCL online seminar of the Center for the Study of Complex Systems, which will be held on Thursday, 24 June 2021 at 14:00 on Zoom. The talk entitled

Electron-hole superfluidity and strongly correlated excitonic phases in double layer systems

will be given by Dr. Sara Conti (Department of Physics, University of Antwerp, Belgium). Abstract of the talk:

In recent years there have been a lot of theoretical and experimental studies in double electron-hole layers. Systems include GaAs double quantum wells (DQW) [1] and, more recently, double graphene bilayers (DBLG) [2], double transition metal dichalcogenides (DTMD) [3] and Ge-Si heterostructures [4]. A big motivation for the studies has been that a Coulomb interaction generate bound states of electron-hole pairs in these solids. These may condense into a superfluid/BEC at low temperatures, and there is now experimental evidence that this indeed happens. In this talk we will discuss the efforts done in these systems to maximize the strength of the electron-hole pairing with the aim to increase the critical temperature for superfluidity [5, 6].

To study electron-hole superfluidity, most of the attention has focused on minimizing the layer separation. However, the full zero-temperature phase diagram that encompasses very large values of separation also is extraordinarily rich. The phases include coupled electron-hole plasma liquid, electron-hole superfluid, exciton supersolid, and coupled electron-hole Wigner crystals. The second significant parameter of the phase space is the average spacing between the electrons or holes within their layers, that can be experimentally tuned by controlling the density. We will present the unified phase diagram for systems with equal carrier densities and equal masses, and map out the phase boundaries.

[1] S. Saberi-Pouya et al., Phys. Rev. B 101, 140501(R) (2020).
[2] A. Perali, et al., Phys. Rev. Lett. 110, 146803 (2013); S. Conti et al., Phys.  Rev. B 99, 144517 (2019).
[3] S. Conti et al., Phys. Rev. B 89, 060502(R) (2020).
[4] S. Conti et al., npj Quantum Materials 6, 41 (2021).
[5] S. Conti et al., Condens. Matter 5, 22 (2020).
[6] M. Van der Donck et al., Phys. Rev. B 102, 060503(R) (2020).

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