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140.120.11.120 1 Y. W. Suen ( 孫允武 ), a W. H. Hsieh( 謝文興 ), a,b S. Y. Chang ( 張紓語...
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Transcript of 140.120.11.120 1 Y. W. Suen ( 孫允武 ), a W. H. Hsieh( 謝文興 ), a,b S. Y. Chang ( 張紓語...
1140.120.11.120
Y. W. Suen ( 孫允武 ) ,a W. H. Hsieh( 謝文興 ),a,b S. Y. Chang ( 張紓語 ), b
L. C. Lee ( 李良箴 ) , b C. H. Kuan ( 管傑雄 ) , a B. C. Lee ( 李秉奇 ) , c and C. P. Lee ( 李建平 ) c
bDepartment of Physics, National Chung Hsing University, Taichung, Taiwan, R.O.C.
aDepartment of Electrical Engineering, National Taiwan University, Taipei, Taiwan, R.O.C.
cDepartment of Electronics Engineering, National Chiao Tung University, Sinchu, Taiwan, R.O.C
High-Frequency Dynamic Magnetotransport Properties of Quantum Wires
2140.120.11.120
OUTLINES
1. Introduction-- What is edge magnetoplasmon (EMP)?-- Previous works about EMP of low-dimensional electron systems (LDES’s).
2. Experimental setup-- Development of high-sensitive microwave vector detection system at an extremely low-power level.
3. EMP excitations in quantum-wire array
4. Conclusions
3140.120.11.120
3D plasma
restoring force field!!
charge flow
m
enp
2
D32dispersion:
2
22
10
31)(
p
Fp
must be long enough!
2
q
4140.120.11.120
2D plasma
~/|q|
qm
enp
2
2D22
When |q| decreases, the restoring force decreases too.
Ej xx
For 2DES in GaAs/AlGaAs, n2D=3x1011 cm-2, 2/|q| =10um, fp=100GHz.
5140.120.11.120
2D magnetoplasma
~/|q|
xxxx Ej
Bxyxy Ej
m
eBq
m
encp
cpmp
22
D22
222
2
The restoring force is enhanced by the magnetic field.
6140.120.11.120
Edge magnetoplasma (EMP) in a finite 2DES
B
EFE
EXB
drift
B
B
PB
EP
f
1
~
BE
Scattering between the bulk 2D and the edge may damp the oscillation.
Confinement potential may affect the group velocity of the edge electrons.
EMP is in the RF or microwave frequency range.
e-
EB
xyxx
7140.120.11.120
First Observation of EMP
Observation of Bulk and EMP in two dimensional electron fluidD. B. Mast, A. J. Dahm, and A. L. Fetter, PRL 54, 1706-1709 (1985)
A 2DES on the surface ofLiquid Helium placed in aperpendicular B-field.
B ≠ 0
B = 0
BfEMP1
8140.120.11.120
B
il
pq
B
Oql
B
EMP
xx
xy
xyEMP
/1
Field-B strongIn
.2/
,/2
,/1
)1(2
ln2
),(
0
0
JEPT Lett., 42, 557 (1985)
depend on the details of the confinement potential.
depend on the scattering and interactions.
9140.120.11.120
Quantum Hall Effect (QHE) provides a very unique platform to study EMPs. EMP is also a very unique tool for studying the edge states of QHEs.
EF
Edge Channels
c
Landau level spacing
10140.120.11.120
JEPT Lett., 57, 587 (1993)
WELE
Ej
fjiji
yx
xy
/,/
0,0
1122
21
0)(
))((22
2221212
WL
f
L
f
Wi xyxxxx
11140.120.11.120
For >>1, L>>W
22
2
2
12
22
22212
0
2/1202,1
4
,)(
)1(
xyxx
xx
xyxx
fW
L
WL
f
i
Lm
ne
Wm
ne
clowcup
2
22//
212
222//
22222
,
/,
For 1, L>>W
12140.120.11.120
Edge-magnetoplasmon excitations in GaAs-AlxGa1-xAs QWsI. Grodnensky, D. Heitmann, K. v. Klitzing, K. Ploog, A. Rudenko, and A. Kamaev
,PRB, 49, 10778-10781 (1994).
540nm×4.5mm
13140.120.11.120
Detection by Coplanar Waveguide (CPW) Sensors
The CPW is patterned by photolithography.There are about 60 alignment keys along the CPW.
Quantum wire array is patterned by e-beam lithography.
14140.120.11.120
T =0.3K
Detection by Phase-Locked Loops (PLL)
Type-II PLL
Sample under detection
phase=1=11PLL system
s=ss
0 =1+ s =11
+s(B)s
0 =0=1+ s(B) =11+s(B)s
B: the parameter (magnetic field) sweeping in the experiment: phase velocity of the signal in coaxial cable
sample
known /1
15140.120.11.120
Pulsed Microwave PLL and Gated Average System
1.2.
(mixers)
Schematic of a homemade PLL system for microwave signals up to 18 GHz.
The phase resolution is about 0.001 degree even at very low average input power level (~ -100dBm).
A special designed homodyne amplitude detection scheme allows us to detect very small microwave adsorption (smaller than 0.005%).
16140.120.11.120
A homemade PLL-MW system(50M-21GHz)
17140.120.11.120
Comparing with commercial vector meters
T=0.3K
1. Better than a commercial VNA at an extremely low-power level !!
2. The resolutions achieved here are better than 0.005% (0.0087dB) for amplitude variation and 0.001
O for phase
with a very low-average power (about -100dBm) into the sample.
18140.120.11.120
0 2 4 6 8 10 0 2 4 6 8 10
0.2%
256MHz
0.2o
0.4%
548MHz
0.2o
0.1% 598MHz
0.2o
A
0.2% 831MHz
B (Tesla)
-
0.2o
B (Tesla)
Observation of EMP in a QW arrayAbout 7000 QWs (0.7μm×20μm) in the gaps of CPW
2 1 2/32 1 2/3(a) (b)Result for a 2DES
19140.120.11.120
0.2 0.4 0.6 0.8 1.0
0.5o
B-1 (Tesla-1)
0.2 0.4 0.6 0.8 1.0
0.5%
-1*
A
B-1 (Tesla-1)
1.91GHz
133MHz
Landau levelfilling factor321 4 321 4
20140.120.11.120
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
0.0 0.2 0.4 0.6 0.8 1.0
B-1 (Tesla-1)
f (G
Hz)
The peak-positions1 2 3 4 Landau Level
Filling Factor
No SdH peaks were detected in this region.
T=0.3KSdH oscillation is screened by EMP!!!
21140.120.11.120
22140.120.11.120
adsorption
phase
23140.120.11.120
Polarizability or susceptibility
22
2
)(
j
jf
m
eelectronic
2/1
2
2
0
0
2
2
)or (
E
VC
ZN
a
s
(f)j
24140.120.11.120
25140.120.11.120
0.0
0.5
1.0
1.5
2.0
0 1 2 3 4 5 6 7 8
0.0
0.5
1.0
1.5
2.0
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
A (%)
Lm3979C62004/04/14
f (G
Hz)
B (Tesla)
-1.6-1.5-1.4-1.3-1.2-1.1-1.0-0.9-0.8-0.7-0.6-0.5-0.4-0.3-0.2-0.10
A (%)
f (G
Hz)
B-1 (Tesla-1)
-1.6-1.5-1.4-1.3-1.2-1.1-1.0-0.9-0.8-0.7-0.6-0.5-0.4-0.3-0.2-0.10
22
2
2
12
22
22212
0
2/1202,1
4
,)(
)1(
xyxx
xx
xyxx
fW
L
WL
f
i
26140.120.11.120
B20m
700nm
-0.4 -0.2 0.0 0.2 0.4 -0.4 -0.2 0.0 0.2 0.4
0.5%1.8G
0.4%3.1G
0.4%6.4G
2%
A
9.9G
0.5%
13.2G
3%14.2G
0.5%
B (Tesla)
17.5G
0.04o
0.2o
0.4o
1o
1o
2o
B (Tesla)
2o
MW
Sample A
27140.120.11.120
-0.4 -0.2 0.0 0.2 0.4 -0.4 -0.2 0.0 0.2 0.4
0.2%9.05GHz
0.1%12.1GHz
0.1%12.5GHz
0.1%
A
13.5GHz
0.2%14.7GHz
0.1%
16GHz
0.5%
B (Tesla)
18GHz
0.2o
0.1o
0.5o
0.5o
1o
0.5o
B (Tesla)
0.5o
B
20m
700nm
MW
Sample B
28140.120.11.120
1. We observed EMP excitations in a QW array with a homemade very-high-sensitivity vector detection system.
2. The low-frequency part of the data can be explained by Mikhailov’s theory, while the high-frequency part exhibits a 2DES-like behavior. We mapped out the transition in between, which is not included in the simple theory.
3. We measured the polarizability of a QW array.