Download presentation

Presentation is loading. Please wait.

Published byIsaac Smith Modified over 4 years ago

1
Exciton formation in graphene bilayer PHYSICAL REVIEW B 78, 045401 (2008) Raoul Dillenschneider, and Jung Hoon Han Presented by Wan-Ju Li 02/25/2009 PHYSICAL REVIEW B 78, 121401(R) (2008)

2
Outline Introduction Main work Summary and Conclusion Assumptions and Comments Excitonic Superfluidity

3
Introduction Exciton: Bound state of an electron and an hole in an insulator or semiconductor ; Coulomb-correlated electron-hole pair. Exciton in bilayer systems(semiconductors): J. P. Eisenstein and A. H. MacDonald, Nature London 432, 691 (2004) 1.Strong magnetic field 2.All electrons reside in the lowest Landau Level 3.Electron-hole pairs form because of Coulomb attraction

4
Introduction(cont.) Why Graphene? 1. It is atomically two dimensional. 2. Perfect particle-hole symmetry 1.Lecture note 1 of phy570X; 2.2. E. McCann, D.S.L. Abergel, and Vladimir I. Falko,European Physical Journal-special topics 148, (2007)

5
Main work The possibility of an excitonic instability in the biased graphene bilayer in the framework of Hartree-Fock theory Bernal stacking

6
Main work (cont.) :The bare kinetic energy within the monolayer

7
Main work-nearest (U1)

8
Main work-nearest (U1)(cont.)

9
Main work-second nearest(U2)

10
Main work-(U2)(cont.)

11
Summary and Conclusion The short-ranged Coulomb interaction was introduced for both nearest U1 and second nearest U2 between the two layers. The critical strength is U1c / t ~3.5 for a bias V/t~1; U2c / t~1.5 at V/ t~1. Doping by applying the voltage difference between the bilayer can control the excitonic properties of the graphene bilayer. intercalation of nondoping and insulating atomic layers between the carbon layers could reduce significantly in such a way that the screened Coulomb interaction U obeys the condition U>Uc and excitons could form.

12
Assumptions and Comments Band truncation (Low energy approximation) short-range Coulomb interaction: up to second nearest neighbor Same-spin electron-hole exciton Interlayer distance? Consider U1 and U2 separately Using different order parameters in the calculations for U1 and U2 cases Exciton formation and BEC

13
Superfluidity Bose-Einstein Condensation of Excitons Room-temperature superfluidity in Graphene bilayer system 1. Hongki Min, Rafi Bistritzer, Jung-Jung Su, and A. H. MacDonald, Physical Review B 78, 121401(R) (2008); 2. J. P. Eisenstein and A. H. MacDonald, Nature 432, 691 (2004); 3. Jung-Jung Su and A. H. MacDonald,Nature Physics 4, 799 (2008)

Similar presentations

OK

Coulomb excitations in AA- and AB-stacked bilayer graphites.

Coulomb excitations in AA- and AB-stacked bilayer graphites.

© 2018 SlidePlayer.com Inc.

All rights reserved.

To make this website work, we log user data and share it with processors. To use this website, you must agree to our Privacy Policy, including cookie policy.

Ads by Google

Ppt on nitrogen cycle and nitrogen fixation definition Ppt on central limit theorem in statistics Ppt on pre ignition symptoms Ppt on biodiversity in india Ppt on building construction process Ppt on network theory sociology Ppt on water softening methods Download free ppt on environment Ppt on misuse of science and technology Ppt on amplitude shift keying block