Excitons in Electrostatic Lattices M. Remeika 1 , L.V. Butov 1 , M. Hanson 2 , A.C. Gossard 2 1 University of California San Diego, Department of Physics 2 University of California, Santa Barbara, Materials Department APS March Meeting 2011
Indirect Excitons More about indirect excitons: d Bound pair of an Excitons in moving lattices electron and a hole confined to separate J. Leonard, 10:24 AM, Wednesday quantum wells Room C144, P32 Excitation energy dependence of the exciton inner ring Y. Kuznetsova, 12:39 AM, Friday, Room D163, Z22 Indirect Exciton Spin Texture in a Cold Exciton Energy is Gas controlled by applied voltage: A. High, 10:48 AM, Friday, �� � ��� � Room D171, Y15 Excitons in Electrostatic Lattices Slide 2/9
Electrostatic Lattice for Indirect Excitons Depth controlled in-situ by Other controlled parameters voltage • Interaction strength • High speed control • Effective mass Structure determined by • Exciton lifetime electrode pattern • Exciton temperature • Arbitrary lattice structures Excitons can cool down below temperature of quantum degeneracy • Compatible with Another system with many semiconductor processing controllable parameters: cold technology atoms in optical lattices Exciton number controlled by • Cold particles laser power • Tunable lattice depth • Selective loading to individual lattice sites • Could emulate properties of condensed matter systems Excitons in Electrostatic Lattices Slide 3/9
Excitons in an Electrostatic Lattice Linear Lattice M. Remeika, J. C. Graves, A. T. Hammack, A. D. Meyertholen, M. M. Fogler, L. V. Butov, M. Hanson, A. C. Gossard PRL , 102,186803 (2009) Excitons in Electrostatic Lattices Slide 4/9
Two Dimensional Lattice Design Two Dimensional Lattice Linear • Different lattice structures Lattice • Onsite interaction (dipole blockade – Coulomb blockade) Square Triangular Honeycomb U ex High Low Excitons in Electrostatic Lattices Slide 5/9
Two Dimensional Lattice Design Applied to a Lattice Potential: Method of Potential • Lattice structure determined by electrode Control by Electrode design Density • Independently controlled lattice depth and base energy Snowflake • Electrode pattern fabricated in a single trap lithography step Exciton V 2 =-2V V 1 =-4V Energy -22meV Parabolic Potential Y. Y. Kuznetsova, A. A. High, V 2 2μm L. V. Butov APL, 97, 201106 (2010) V 1 -34meV Excitons in Electrostatic Lattices Slide 6/8
SEM Images 5μm Square Triangular Honeycomb Excitons in Electrostatic Lattices Slide 7/9
Preliminary Data on Excitons in a 2D Lattice Work in progress 0 meV High Energy 1.550 Emission Energy (eV) 0.8 meV Emission 1.7 meV 2.5 meV 1.545 3.4 meV 4.2 meV Low Energy 1.540 Emission 1.535 1 10 100 1000 Laser Power ( W) Linear lattice Measured by Measured by Controlled by Controlled by exciton exciton voltage voltage energy shift energy shift Excitons in Electrostatic Lattices Slide 8/9
Conclusions • Developed a method to create 2D electrostatic lattices for excitons. • Realized square, triangular, and honeycomb lattices. • Analysis of exciton localization-delocalization transition as a function of exciton density and lattice amplitude is in progress. Excitons in Electrostatic Lattices Slide 9/9
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