The effect of disorder in superfluid double layer graphene

Dellabetta, Brian; Gilbert, Matthew J.

doi:10.1088/0953-8984/23/34/345302

Cited by 5 publications

(4 citation statements)

References 66 publications

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“…This work 19 provides a comprehensive study on the effect of short-range scatterers in double layer graphene systems that must be taken into account for this system to be experimentally realized. Unfortunately, room temperature condensation is subject not only to defects in fabrication, but also carrier-phonon interactions.…”

Section: Final Scientific Accomplishments: Dipolar Superfluids In mentioning

confidence: 99%

Progress Report for Grant Number W911NF-09-1-0347 (University of Illinois - Urbana)

Gilbert¹

2012

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Section: Final Scientific Accomplishments: Dipolar Superfluids In mentioning

confidence: 99%

Progress Report for Grant Number W911NF-09-1-0347 (University of Illinois - Urbana)

Gilbert¹

2012

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“…First, the critical temperature (T c ) may simply be too small (i.e., much lower than the optimistic mean-field theoretic predictions for ideal systems) and therefore the condensate is destroyed by simple thermal fluctuations. Second, it is possible that disorder in the form of electron-impurity scattering, 8,9 scattering from vacancy sites in the lattice, 10 or from the presence of inhomogeneity in the charge density distribution 11 is suppressing formation of the condensate. In this work, we examine the last of these possibilities.…”

Section: Introductionmentioning

confidence: 99%

Interlayer excitonic superfluidity in graphene

et al. 2013

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We discuss the conditions under which the predicted (but not yet observed) zero-field interlayer excitonic condensation in double layer graphene has a critical temperature high enough to allow detection. Crucially, disorder arising from charged impurities and corrugation in the lattice structure -invariably present in all real samples -affects the formation of the condensate via the induced charge inhomogeneity. In the former case, we use a numerical Thomas-Fermi-Dirac theory to describe the local fluctuations in the electronic density in double layer graphene devices and estimate the effect these realistic fluctuations have on the formation of the condensate. To make this estimate, we calculate the critical temperature for the interlayer excitonic superfluid transition within the mean-field BCS theory for both optimistic (unscreened) and conservative (statically screened) approximations for the screening of the interlayer Coulomb interaction. We also estimate the effect of allowing dynamic contributions to the interlayer screening. We then conduct similar calculations for double quadratic bilayer graphene, showing that the quadratic nature of the low-energy bands produces pairing with critical temperature of the same order of magnitude as the linear bands of double monolayer graphene.

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“…After the system passes the interlayer voltage corresponding to the critical current, the interlayer current plummets as the system can no longer sustain the condensate phase and interlayer tunneling becomes dominated by single-particle tunneling [16], [23]. We plot the interlayer current-voltage characteristic calculated for two values of gate voltage in Fig.…”

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confidence: 99%

Phonon limited transport in graphene pseudospintronic devices

Estrada

Dellabetta

Gilbert

2012

70th Device Research Conference

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Abstract-A predicted room-temperature phase transition from Fermi liquid to dissipationless Bose-Einstein exciton superfluid suggests that graphene pseudospin devices may have the potential to far outperform traditional CMOS devices. When examining the possibility of a room-temperature exciton condensate, it is important to consider scattering of charge carriers by phonons in each of the constituent graphene monolayers. Using the nonequilibrium Green's function formalism, we examine the effect that carrier-phonon scattering has on device performance. We find that the effect of carrier-phonon scattering has strong dependence on the device coherence length. As such, for large gate voltages, the effect of phonons on interlayer transport is negligible.Index Terms-Critical current, nanoelectronics, phonons, tunneling. IT IS generally accepted that MOSFET scaling cannot continue unabated. In light of this, one of the most active areas of semiconductor electronics research is post-CMOS device technology. A variety of post-CMOS devices are under active consideration. In an effort to reach the smallest possible dimensions, molecular electronics has gained serious attention. While molecular electronics offers high device density and lowpower operation, issues surrounding the molecule-electrode coupling, low yield, and three-terminal device fabrication [1] plague development. Improvements in nanoscale fabrication techniques have sparked interest in replacing CMOS with nanoelectromechanical systems (NEMSs). NEMSs offer small leakage current and a large on-off ratio [2]; however, highfrequency switching speed and reliability remain unsolved challenges. Beyond these relatively exotic solutions, the tunnel field-effect transistor (TFET), whose operation is based on band-to-band tunneling [3], has shown much recent progress. TFETs showcase a low OFF-state current and a subthreshold slope experimentally demonstrated to be less than 60 mV/dec for carbon nanotube TFETs. However, TFETs also possess a low ON-state current, which must be significantly improved if these devices are to be implemented in information processing technologies. Graphene-based pseudospintronic (G-PsS) devices are predicted to exhibit a high ON-state current with low-power dissipation [4]- [6]. It has been proposed that G-PsS devices could outperform traditional CMOS as they operate based on coherent interlayer transport rather than on the principle of source injected charge based on thermionic emission. In some works, graphene-based pseudospin devices have been predicted to possess a room-temperature phase transition from normal Fermi liquid behavior to a Bose-Einstein condensate of indirectly bound excitons formed when electrons present in one layer bind with an equal number of holes in the other layer [7]-[9]. The transition temperature has not been theoretically resolved [10], and other works predict an orders-of-magnitude lower transition temperature [11]. Still, recent Coulomb drag experiments have provided evidence of the interlayer interactions which ...

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The effect of disorder in superfluid double layer graphene

Cited by 5 publications

References 66 publications

Progress Report for Grant Number W911NF-09-1-0347 (University of Illinois - Urbana)

Progress Report for Grant Number W911NF-09-1-0347 (University of Illinois - Urbana)

Interlayer excitonic superfluidity in graphene

Phonon limited transport in graphene pseudospintronic devices

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