Stability of Sarma phases in density imbalanced electron-hole bilayer systems

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Subaşı, Ahmet Levent and Pieri, P. and Senatore, G. and Tanatar, B. (2010) Stability of Sarma phases in density imbalanced electron-hole bilayer systems. Physical Review B, 81 (7). ISSN 1098-0121

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Official URL: http://dx.doi.org/10.1103/PhysRevB.81.075436


We study excitonic condensation in an electron-hole bilayer system with unequal layer densities at zero temperature. Using mean-field theory we solve the Bardeen-Cooper-Schrieffer (BCS) gap equations numerically and investigate the effects of intralayer interactions. The electron-hole system evolves from BCS in the weak coupling limit to Bose-Einstein condensation (BEC) in the strong coupling limit. We analyze the stability of the Sarma phase with k,-k pairing by calculating the superfluid mass density and also by checking the compressibility matrix. We find that with bare Coulomb interactions the superfluid density is always positive in the Sarma phase, due to a peculiar momentum structure of the gap function originating from the singular behavior of the Coulomb potential at zero momentum and the presence of a sharp Fermi surface. Introducing a simple model for screening, we find that the superfluid density becomes negative in some regions of the phase diagram, corresponding to an instability toward a Fulde-Ferrel-Larkin-Ovchinnikov-type superfluid phase. Thus, intralayer interaction and screening together can lead to a rich phase diagram in the BCS-BEC crossover regime in electron-hole bilayer systems.

Item Type:Article
Additional Information:Article Number: 075436
Subjects:Q Science > QC Physics > QC1 General
ID Code:15080
Deposited By:Ahmet Levent Subaşı
Deposited On:08 Nov 2010 14:40
Last Modified:29 Jul 2019 10:52

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