Heat Flow Control : from Thermal Transistor to Thermal Logic Gate

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Heat Flow Control from Thermal Transistor to
Thermal Logic Gate
Wang Lei
Department of Physics, Renmin University of
China, Department of Physics and Centre for
Computational Science and Engineering, National
University of Singapore
Transmission of Information and Energy in
Nonlinear and Complex Systems (TIENCS) 2008
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Motivation
When it comes to transporting energy, nature
has two vital tools conduction by heat and by
electricity. Electricity, by way of the
electronic transistor and other devices that
control the flow of charge, has enabled
technological developments that have improved
many aspects of our lives. But similar devices
that allow the flow of heat to be controlled
are still not available.
To make thermal devices that control heat flow
just like what we have done for electric charge
flow.
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Outline
1 Negative Differential Thermal Resistance 2
Model of Thermal transistor 3 Thermal Logic Gate
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1 Negative Differential Thermal Resistance (NDTR)
1.1 WAHT is Negative Differential Thermal
Resistance
When temperature difference exists, heat flows
from high temperature to low temperature,
Normally larger the temperature difference,
larger the heat current J, namely positive R.
Is the negative R, i.e., lower temperature
difference higher heat flow, possible?
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A water pipe
High pressure, high flow.
Low pressure, low flow.
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Pressure dependent valve
high pressure
high flow
?
narrow valve
low flow
low pressure
low flow
?
broad valve
high flow
Two factors compete, negative differential
resistance is thus possible!
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1.2 How to Make a Negative Differential Thermal
Resistance
Make a smart thermal valve.
Match and mismatch of the power spectra of
coupled materials
Resonance phenomenon
Then, the response
?
?0
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As the frequency of the external driven force
equals the own frequency of the linear
oscillator, the response reaches its maximum.
As the power spectra of two systems match each
other, energy can easily flow from one to the
other.
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Suppose the power spectra of one of the two
coupled segments is temperature dependent.
TL
TLltTR
TR
Smaller TL larger ?T
Large TL smaller ?T
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In principal power spectra of any nonlinear
system is temperature dependent.
Our choice Frenkel-Kontorova (FK) model
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Sensitive temperature dependence
Low frequency
When the energy of particles is more or less the
critical value, the temperature dependence
reaches its maximum. Then we can see clear NDTR.
High frequency
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(No Transcript)
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1.3 Why do we need a Negative Differential
Thermal Resistance?
Thermal transistor
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2 Model of Thermal transistor
2.1 Field-Effect-Transistor (FET)
VD()
D(Drain)
ID
IG
?
VG
G(Gate)
IS
S(Source)
VS(-)
IG 0
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Segment D
Segment S
JS
JD
O
TST-
TDT
TO
TgtT-
At steady state JSJD
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current amplification factor
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Normal situation RS,RDgt0 Therefore alt1
The transistor does NOT work!!
If either RS or RD is negative, acan be greater
than 1 thus the thermal transistor works.
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RG is negligible thus TOTG
Heat flow switch
At the three crosses, JG0.
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Heat flow modulator
In the working region TG 0.05 0.135
JD5e-52e-4 While JG-1e-51e-5
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3 Thermal Logic Gate
3.0 standard voltages (temperature)
Transistor-transistor logic (TTL) Vhigh5.0 v,
Vlow0.0 v
Here we use Ton and Toff as the two standard
temperatures.
3.1 Thermal repeater
A repeater standardize the input, when it is
slightly different from Ton /Toff.
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suppose TG is slightly greater than Ton, then
JSgtJD, thus JG gt0
suppose RG is taken into account, Then TOltTG,
thus is closer to Ton.
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As TG is closer to Ton/Toff, TO is always even
closer, i.e., Ton and Toff are two stable fixed
points of the function TO(TG)
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If we connect them in series, the final output
will be closer and closer to that of an ideal
repeater.
Output of a six-transistor repeater
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3.2 Thermal NOT gate
Notice as Tin increases, Tout however decreases.
Question can we cool down one part of a system
by warming up another part?!
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This is in fact possible.
Lets study TO(TO).
TO increases
JD increases, RD is nearly fixed
Temperature drop in segment D ( TD-TO ) increases
TD is fixed, thus TO decreases
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VoutVR2/(R1R2)
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3.3 Thermal AND/OR gate
AND/OR gate is a three terminal ( two inputs one
output) device.
If two inputs are the same, the output of AND/OR
gate follows, otherwise AND/OR gate output
off/on.
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It is clear that when the two inputs are the
same, the output must follow.
By adjusting some parameters e.g., the critical
temperature of the repeater, it is also easy to
output off/on, thus a AND/OR gate is realized.
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Summary
Based on the novel physical phenomenon
Negative Differential Thermal Resistance, thermal
transistor that control heat flow becomes
possible. By combining thermal transistor in
different ways, one can also build up thermal
logic gates that realize all the basic logic
operations. Although at this moment these are
only pure theoretical (toy) models, this still
opens the possibility that, heat energy already
present in abundance in electronic devices, can
be used to process information and even to do
computation.
Phononics
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References
Baowen Li, Lei Wang, and Giulio Casati, Appl.
Phys. Lett. 88, 143501 (2006) Lei Wang and
Baowen Li, Phys. Rev. Lett. 99, 177208
(2007) Lei Wang and Baowen Li, Physics World
21, no.3, 27 (2008).
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Acknowledgement
Collaborators
Prof. Baowen LI (NUS) Prof. Giulio CASATI
(NUS/Como, Italy) Dr. Jinghua LAN (NUS,
IHPC/ASTAR) Dr. Nianbei LI (NUS) Mr. Nuo YANG
(NUS) Mr. Weichung LO (NUS, IHPC/ASTAR) ...... Ot
her members in CCSE.
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Renmin University of China
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Renmin ?? peoples
??????? Peoples Republic of China
Our university is basically a social science
university.
We are building a department of physics in a
social science university.
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Groups in our department
1, theoretical physics 2, condensed matter
experiment 3, material computation and
simulation 4, computational physics 5, atomic and
molecular physics 6, complex systems statistical
physics, finance physics, bio-physics etc.
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A young department needs your support Welcome to
Renmin University Welcome to our department
Wang Lei phywanglei_at_ruc.edu.cn
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thanks