Quantum Dots - Centre for High Energy Physics

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Quantum Dots
Arindam Ghosh
Physics research on quantum dots
What are the active areas
•
•
•
•
Understand nanoscale transport
Materials
Self-assembly of nano-structures
Paradigm shift in functional
electronics?
Singlenanostructured
Organization
Effect
New
of
electron
quantum
of large
number offor
mechanics
materials
transistors
nanostructures
Confinement
transistors:
Carbon
for next
Beyond
and
–
scalabilityforce
Coulomb
silicon?
generation?
Utilize
Nanowires
New
Spin architecture?
effects
natural
for
and
forces
Organic,magnetism
intrinsic
interconnects
Electronics
inorganic
with
or active
and
biological–systems
Disorder
elements
nanomachines?
error
optimization
New
Ferromagnetic
dielectrics:
and
logic
high-k
modeling
and
devices?
low-k
Quantum computation
Single electron transistors (SET) –
Operation of atomic switches
Quantum Dot
Gate
Source
Drain
VSD
Particle in a small box ~ 10 – 100 nm
Energy-levels are quantized
DE ~ 1/L2
Quantum effects only when DE>>kT
VSD
current
current
Drain
current
Source
-Vg
VSD
Gate voltage (Vg)
Source-drain voltage (VSD)
The top-down approach
Materials
Plus
Plus
Creates
Plan/Information
Tools
Product
The bottom-up approach
Self-Assembled
Product
Creates
Plus
Tools
Materials with stored
information
New materials and protocols
for SET
1. High-mobility two-dimensional electron
gas
2. Nano-engineering with silicon
3. Semiconductor nanoparticles and
nanowires
4. Carbon electronics with nanotubes and
graphene
5. Molecules and DNA
The two-dimensional electron gas in
semiconductor heterostructures
Si atoms
Aluminum
Gallium Arsenide
2D electrons
Gallium
Arsenide
Extremely versatile
Expensive
Incompatible to Silicon technology
Carbon nanotubes
The Carbon nanotube single electron
transistor
Source
Drain
Gate
Single electron transistor with nanotube rope
Structures of Quantum dot
Transport in single quantum dots
Constant interaction model
Coulomb blockade oscillations
The magic numbers
The Fock-Darwin Spectrum
Experiment
Excitation spectrum
Quantum dot in quantum computation
1. Spin qubit in single quantum dot
2. Charge qubit in double quantum dots
3. Varying readout schemes
Spin measurement in a quantum dot
“Spin to charge” conversion
Nature 2004
The protocol
(1) Empty, (2) inject and wait, (3) measure
Measuring spin
Experiment
2D Artificial Atoms
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