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Excitons in Electrostatic Lattices Flipbook PDF
Excitons in Electrostatic Lattices M. Remeika 1, L.V. Butov ,M. Hanson 2, A.C. Gossard2 1University of California San Di
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Excitons in Electrostatic Lattices M. Remeika1, L.V. Butov1 , M. Hanson2, A.C. Gossard2 1University
of California San Diego, Department of Physics 2University of California, Santa Barbara, Materials Department
CLEO:QELS 2012
Indirect Excitons d
Bound pair of an electron and a hole confined to separate quantum wells Long lifetime
Can cool down below temperature of quantum degeneracy
Indirect Exciton Energy is controlled by applied voltage:
More about indirect excitons: Transport of Indirect Excitons in a Potential Energy Gradient QM1G.7 Y. Kuznetsova, Monday, 9:45am, A7
Spontaneous Coherence of Indirect Excitons in a Trap QTu3D.3 A. High, Tuesday , 5:15pm, A4.
Spontaneous coherence in a cold exciton gas QTh4E.4 A. High, Thursday, 5:15pm, A5.
Excitons in Electrostatic Lattices
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Electrostatic Lattices for Indirect Excitons Depth controlled in-situ by voltage • High speed control
Structure determined by electrode pattern • Arbitrary lattice structures • Compatible with semiconductor technology
Exciton number controlled by laser power • Selective loading to individual lattice sites
Other controlled parameters • • • •
Interaction strength Effective mass Exciton lifetime Exciton temperature
Excitons in lattices – a condensed matter system with controllable parameters
Another system with controllable parameters: cold atoms in optical lattices • Cold particles • Tunable lattice depth • Used for emulation of condensed matter systems
Excitons in Electrostatic Lattices
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Electrostatic Lattice Design Linear Lattices
Two Dimensional Lattices • Different lattice structures Square
Triangular
Honeycomb
Uex High
Low Excitons in Electrostatic Lattices
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Two Dimensional Lattice Design Applied to a Lattice Potential: • Lattice structure determined by electrode design • Independently controlled lattice depth and base energy • Electrode pattern fabricated in a single lithography step Exciton
Method of Potential Control by Electrode Density Snowflake trap
V2=-2V V1=-4V
Energy
-22meV Parabolic Potential
Y. Y. Kuznetsova, A. A. High, L. V. Butov, APL 97, 201106 (2010)
V2 V1
2μm -34meV Excitons in Electrostatic Lattices
Slide 5/10
Proof of Principle for 2D Lattices for Excitons
ħ (meV) I (arb. unit)
• Realized 2D lattice for indirect excitons • Excitons collect to lattice sites • Lattice potential is in agreement with simulation
1.0 0.9
0.02 0.01 0.00
Simulation
-3
-2
-1
0
x (m)
1
2
3
M. Remeika, M. M. Fogler, L. V. Butov, M. Hanson, A. C. Gossard, APL 100,061103 (2012) Excitons in Electrostatic Lattices
Slide 6/10
Exciton localization Linear
Square
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)
at loc-deloc transition
Interaction energy
M. Remeika, M. M. Fogler, L. V. Butov, M. Hanson, A. C. Gossard, APL 100,061103 (2012)
Lattice depth
Excitons in Electrostatic Lattices
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Superfluid – Mott Insulator Transition for Excitons in an Electrostatic Lattice 0.8
2
0.35
Inter-site hopping
Exciton mass
0.12
On-site interaction
Lattice constant T = 50 mK b = 200 nm Experimentally accessible!
Superfluid – Mott insulator transition for atoms in an optical lattice M. Greiner, O. Mandel, T. Esslinger, T.W. Hansch, I. Bloch, Nature 415, 39 (2002)
M. Remeika, M. M. Fogler, L. V. Butov, M. Hanson, A. C. Gossard, APL 100,061103 (2012) Excitons in Electrostatic Lattices
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Work in Progress: Exciton Coherence in a Lattice • Spatially resolved coherence measurement using Mach–Zehnder interferometer. • Long-range coherence. CCD Signal
Lattice lines
1
2
Interference fringes
Excitons in Electrostatic Lattices
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Conclusions • Developed a method to create 2D electrostatic lattices for excitons. • Demonstrated 2D lattices for excitons. • Realized coherent exciton gas in a lattice.
Excitons in Electrostatic Lattices
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