1. No category

Highly resistive superconducting
resonators: why and how?
Teun Klapwijk
Kavli Institute of Nanoscience
Delft University of Technology
Astronomical detectors based on
superconductivity
• Photon-assisted tunneling (Herschel Space
telescope and ALMA)
• Thermometer; TES: transition edge sensor +
absorber (SCUBA-II and Spica-Safari)
• Pair-breaking detectors
– STJ’s: tunneljunction readout of excess qp’s (obsolete)
– Create qp’s: look at microwave response: resonators
(talk of the town)
Herschel Space telescope
silicon
germanium
NTD Ge
NTD Ge
Photon-assisted tunneling
N
S
EF
0
V0 + Vω cos ωt
40 GHz
Tien & Gordon, Phys. Rev.129, 647 (1963)
Tunnel-detection elements
Dusted with submillimeter galaxies.
SPIRE-image:
Richards’ First Law
Semiconductor bolometers
Superconducting detectors
CSO and CCAT
Astro2010 Decadal Survey:
• CCAT only project recommended in its class
• Recommended for immediate start
The future
N=106
2022
10’ @ 350 µm
N=105
N=50k
2017
CCAT plan
Titanium Nitride Direct-Absorption MKIDs
CPS feedline
• Cardiff style lumped element resonator
• 90% inductor area, 10% capacitor area
• TiN film on Silicon substrate
t = 40 nm, Rs ~ 20 Ω/□
• High resistivity enables efficient optical
absorption:
a
λ(optical) ~ 350 microns
a ≈ Fλ = 1mm
IRMMW-2010, Rome, 5-10 Sept 2010
18
Figure of merit for LEKID
di ss
α sc τ m ax Qi ,m ax / N 0 Vsc
F =
In addit ion, t he gap parame
• Kinetic induction fraction is high
• Quality factor is high
• Generation-recombination time comparable
Generation-recombination noise
Quasi-particle density:
Recombination rate:
Wilson & Prober 2004
Sergeev et al, APL 80, 817 (2002)
5/13/2011
UCSB Lunchtalk Martinis' group
20
Residual dilute quasiparticle concentration at 100 mK
5/13/2011
UCSB Lunchtalk Martinis' group
21
21
Quality factors
L = µ 0(h + 2λ sc )/ w
2λ sc
α ms =
h + 2λ sc
The magic of TiN
Why TiN ?
• High resistivity (~100 µΩ cm)
– Efficient far-IR absorption with 20-50 nm thick
films and reasonable area filling fraction
– High kinetic inductance fraction
• Tc varies with stoichiometry, 0 - 4.5 K
• Reasonable qp lifetime
– Maximum lifetime varies as ~ Tc2
• Extremely high quality factors, > 107
• Improved figure of merit:
Optical fiber para-amp
• Intensity dependent refractive index
from Hansryd et al. (2002)
Parametric
Versionamplifier
0.1
• 0.8 m NbTiN CPW line
1um
1um
50nm
Utilizing nonlinear kinetic inductance
TiN (NbTiN) Films
• TiN films sputtered (EE-TU Delft); evaluated by
Pascale Diener at SRON
• TiN films sputtered (SRON)
• TiN films from JPL; evaluated by Pascale D.
• TiN ALD films (Delft)
• TiN films sputtered (Delft: Nordiko)
• NbTiN sputtered (Delft)
Teun Klapwijk
TiN-KISS MidYear Program Review May
26th 2011
27
Long range phase coherence
• Quasi-particle excitations (common BCS story)
• Quantum phase fluctuations (Competition
between Coulomb blockade and Josephson
coupling)
• Thermal phase fluctuations (Vortex-antivortex unbinding: Berezinskii-KosterlitzThouless phase transition)
5/13/2011
UCSB Lunchtalk Martinis' group
28
Tunneling experiments in highly resistive
aluminium
Dynes et al, PRL 53, 2437 (1984)
Teun Klapwijk
Labeled: lifetime-effects. Correct?
TiN-KISS MidYear Program Review May
26th 2011
29
“Old” data of Pieter de Visser
and Rami Barends
‘regular’
’ film: D21 C3, sputtered NbTiN (Nordiko)
50 nm, Tc = 13.6 K (∆ = 2057 µeV), ρ = 141 µΩ—cm
Γ = 17 µeV (0.83%), α = 0.39
Teun Klapwijk
TiN-KISS MidYear Program Review May
26th 2011
31
Recent data of Pieter de Visser
‘highly disordered’
’ film: D20, sputtered NbTiN
50 nm, Tc = 11.9 K (∆ = 1800 µeV), ρ = 506 µΩ—cm
Γ = 25 µeV (1.4%), α = 1.23
Teun Klapwijk
TiN-KISS MidYear Program Review May
26th 2011
32
Complete set for NbTiN
200
20
withdynes
nodynes
data
0
Fit error (%)
5
δ f0 / f0 * 10
0
-200
-400
-600
-800
-20
-40
-60
-80
0
0.5
1
1.5
2
2.5
3
-100
3.5
0
0.5
1
1.5
T (K)
2
2.5
3
3.5
T (K)
0
withdynes
nodynes
data
withdynes
nodynes
data
5
10
-20
Qi
δ f0 / f0 * 105
-10
4
10
-30
-40
0.4
0.6
0.8
1
1.2
1.4
T (K)
1.6
1.8
2
2.2
2.4
0.5
1
1.5
2
T (K)
2.5
3
3.5
-4
x 10
5
data
calculation with dynes
calculation nodynes
3
-5
10
d(1/Qi)
d(1/Qi)
4
2
data
calculation with dynes
calculation nodynes
1
-10
10
0
0
Teun Klapwijk
1
2
3
df/f
4
5
-4
6
-3
10
-3
x 10
TiN-KISS MidYear Program Review May
26th 2011
10
df/f
33
Plot for TiN (see Pieter-Jan Coumou’s
poster)
Teun Klapwijk
TiN-KISS MidYear Program Review May
26th 2011
34
Coherent vs incoherent pairing
Sacepe et al,
Nature Physics
7, 239 (2011)
High disorder
Low disorder
Teun Klapwijk
InOx
TiN-KISS MidYear Program Review May
26th 2011
35
Theoretical justification of Gamma?
• Fitting-exercise to smooth out the singularity?
• Lifetime-broadening: ‘old’; obsolete?
• Breakdown of longe range superconducting
coherence: ‘new’
• Most data-taking focuses on tunneling
• New: our use in the complex impedance
Teun Klapwijk
TiN-KISS MidYear Program Review May
26th 2011
36
Physics questions
• Despite high resistivity a very high Q: low
dissipation due to ‘insulator’?
• Saturation of Q at low temperatures?
• Deviations from Mattis-Bardeen accomodated
through ‘gamma’; justification?
• Recombination times: quasi-particles
recombining to Cooper pairs?
• After Oleg’s talk: resonators of InOx?