Vibrating suspended carbonnanotube Josephson junctions Han Keijzers Ciprian Padurariu, Sergey Frolov...
Vibrating suspended carbon nanotube Josephson junctions T<<hf/kB (130mK)114 Q~60.000I (pA) ~50mK ...
Vibrating suspended carbon nanotube Josephson junctions T<<hf/kB (130mK)114 Q~60.000I (pA) ~50mK ...
Macroscopic quantum resonators6.1GHz 7.5GHz 3.7GHzn<0.07 n=0.34 ...
Nanotube quantum resonator?• Large spring constant & small mass: high frequencies ! 2 = k=m ...
Delft nanotube resonators Steele et al. Laird et al. Science 325, 2009 Nano Lett. 12, 2012• CNTs...
Superconductivity & Nanomechanics in CNTs• Nanomechanics: • Shapiro stepsOur group: Science 325,...
First dataset measured: 1 dV/dI(kΩ)I (nA) 0 ...
Josephson mixing??? � 𝑦 � 𝑞 ...
Outline• Fabrication and preselection procedure• Origin of the measured signal – Is it a peculiar non linearity of the sy...
Design• 48 trenches / cell• 25 cells on a 19x19mm2 wafer• 1200 trenches / wafer
Trench fabrication process• 200nm and 250nm trenches: f=1…2GHz
• High yield trench fabrication• Ultraclean CNTs grown at last fabrication step
Low device yield… • position • # across trench ...
Characterization at room temperature April 2010: Vincent Mourik ...
Dipstick characterization 21 17 13 9 V=100μV ...
Dipstick characterization 30Imeas (nA) Device 4 V=750μV ...
Dilution fridge setup• Filtering is important 4 cells/ cooldown RC filters Cu powder filters
1GHz mechanics + 1nA Supercurrent d I/dfdVG (a.u.) 930 ...
Mixing signal on resonance -68 919.140MHz dV/dI(kΩ)P(dBm) ...
Mixing signal on resonance 34 919.175MHz 919.172MHz world record!...
Mixing with Josephson harmonics -58.2dBmNormal contacts ...
Mixing with Josephson harmonics -58.2dBmNormal contacts ...
Is it Josephson mixing?let’s kill superconductivity.
Quench superconductivity: Current bias• Strong bias dependence below Bc Shapiro step ...
Quench superconductivity: Temperature • Signal drops 2 orders of magnitude above Tc T(K) R(kΩ) ∆V(nV) 8.5...
Quench superconductivity: B field 160 1 peaks up peaks down ...
Is it a p- junction?? 𝐼 𝑆 = 𝐼 𝐶 sin 𝜑 + 𝜋 = − 𝐼 𝐶 sin 𝜑 +π -• Noth...
p- junctions 0-junction π-junctionΨ Ψ x ...
p- junctions 0-junction π-junction Zeeman 0-π junctionΨ Ψ ...
2nd device 50 0-state π-state (?) 0V (nV) ...
Is there a smoking gun? let‘s look for the Josephson forceThe Effect of Mechanical Resonance on Josephson Dynamics ...
Mixing and Josephson force 𝐹 𝐽 = −𝛻𝐸 𝐽 Width of 1st Shapiro stepJosephson force ...
Extracting mixing current • Measure resonance peak and IV 1 919.018MHz V(uV) ...
Josephson force: we don’t see it. dV/dI (a.u.) dV (a.u.) dI (a.u....
Conclusion• In our devices there is strong mixing current that can be attributed to Josephson mixing.• We have found Zeem...
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Nanoscience seminar Grenoble March 2012

Published on: Mar 3, 2016
Source: www.slideshare.net


Transcripts - Nanoscience seminar Grenoble March 2012

  • 1. Vibrating suspended carbonnanotube Josephson junctions Han Keijzers Ciprian Padurariu, Sergey Frolov, Gary Steele, Yuli Nazarov, Leo Kouwenhoven
  • 2. Vibrating suspended carbon nanotube Josephson junctions T<<hf/kB (130mK)114 Q~60.000I (pA) ~50mK z.p.m~0.5pm Han Keijzers106 Han Keijzers Ciprian Padurariu, Vincent Mourik, Ciprian Padurariu, Sergey Frolov, Gary Steele, Sergey Frolov, 2.832 Gary Kouwenhoven2.834 2.833 Yuli Nazarov, LeoSteele, Yuli Nazarov, Leo Kouwenhoven Frequency (GHz)
  • 3. Vibrating suspended carbon nanotube Josephson junctions T<<hf/kB (130mK)114 Q~60.000I (pA) ~50mK z.p.m~0.5pm Han Keijzers 10106 Han Keijzers RN=8.7kΩ Ciprian Padurariu, Vincent Mourik, ISW=845pA Ciprian Padurariu, Sergey Frolov, V (µ V) Gary Steele, Sergey Frolov, 2.832 Steele, Yuli Nazarov, Leo Kouwenhoven Gary Kouwenhoven2.834 0 2.833 Yuli Nazarov, Leo Frequency (GHz) ISWRN=7.9μV -10 -1 0 1 I (nA)
  • 4. Macroscopic quantum resonators6.1GHz 7.5GHz 3.7GHzn<0.07 n=0.34 n=0.85Q=260 Q=3.3*105 Q=105AlN resonator coupled Al membrane Si nanobeam in cavityto a sc. qubit dilution fridge laser cooling 20K downdilution fridge 1012 atoms in flow cryostatO’Connel et al. xzpf=4.1fm xzpf=2.7fmNature 464, 2010 Teufel et al. Chan et al. Nature 475, 2011 Nature 478, 2011
  • 5. Nanotube quantum resonator?• Large spring constant & small mass: high frequencies ! 2 = k=m x2 = ~=(2m!) very large zero point motion zpm• Lack of structural / surface defects: high QHuettel et al. Nano Lett. 9 2009: L=800nm, f=300MHz, x_zpm=2pm, Q=140k • Ideal for QD/SET or Josephson junctions
  • 6. Delft nanotube resonators Steele et al. Laird et al. Science 325, 2009 Nano Lett. 12, 2012• CNTs are very sensitive high Q resonators and their motion can be detected at 40GHz
  • 7. Superconductivity & Nanomechanics in CNTs• Nanomechanics: • Shapiro stepsOur group: Science 325, 2009, Here (Wernsdorfer): PRL 99, 2007Nano Lett. 12, 2012 3GHz ± 100MHz to 40GHz
  • 8. First dataset measured: 1 dV/dI(kΩ)I (nA) 0 7 6 5 4 3 -1 2 1 251.5 252.5 253.5 f (MHz) May 2010
  • 9. Josephson mixing??? � 𝑦 � 𝑞 10 Shapiro steps ωRF VSD µ V) VSD 0 ( VG -10 -1 0 1 I (nA)The Effect of Mechanical Resonance on Josephson Dynamics arXiv:1112.5807
  • 10. Outline• Fabrication and preselection procedure• Origin of the measured signal – Is it a peculiar non linearity of the system? – Is it Josephson mixing? – Is there a smoking gun? Josephson force?• Conclusion
  • 11. Design• 48 trenches / cell• 25 cells on a 19x19mm2 wafer• 1200 trenches / wafer
  • 12. Trench fabrication process• 200nm and 250nm trenches: f=1…2GHz
  • 13. • High yield trench fabrication• Ultraclean CNTs grown at last fabrication step
  • 14. Low device yield… • position • # across trench • bandgap ~5 working devices on 1 chip with 1200 trenches• Make 4800 potential devices in 48h• Do a lot of preselection
  • 15. Characterization at room temperature April 2010: Vincent Mourik April/May/June 2011:
  • 16. Dipstick characterization 21 17 13 9 V=100μV 6 5I (nA) 9 13 5 Device 1 1 1 0 0.8 16 20 24 2 34 12 5 8I (nA) 1 0.4 Device 2 0 0.4I (nA) 0.2 Device 3 0 -6 0 6 VG (V)
  • 17. Dipstick characterization 30Imeas (nA) Device 4 V=750μV 0 -8 -4 0 4 8 VG (V) 30 dI/dV (μS) 60 VBIAS(mV) 0 40 20 -30 -8 -4 0 4 8 VG (V)
  • 18. Dilution fridge setup• Filtering is important 4 cells/ cooldown RC filters Cu powder filters
  • 19. 1GHz mechanics + 1nA Supercurrent d I/dfdVG (a.u.) 930 2 920 1 f(MHz) 0 910 mechanics -1 -2 2 -3 supercurrent Ic(nA) 1 0 -12 -6 0 6 12 VG (V)
  • 20. Mixing signal on resonance -68 919.140MHz dV/dI(kΩ)P(dBm) 30 20 10 world record! -34.5 919.200 Q=518k 4 -39dBm dV/dI(kΩ)f(MHz) ∆ V(nV) 919.180 10 2 8 6 4 0 919.139 -2 -.19 919.18 +.19 f(MHz)
  • 21. Mixing signal on resonance 34 919.175MHz 919.172MHz world record! 32 Q=518k 4V (μV) ∆ V(nV) 2 ΔV~200nV 30 0 -2 -.19 919.18 +.19 f(MHz) 28 4 4.4 4.8 I(nA)
  • 22. Mixing with Josephson harmonics -58.2dBmNormal contacts 961.7 ωRF 1ωr V (µV) Signal power f (MHz) 0.4 0 961.1 -43dBm -0.2 0 ωG ω 480.9 ωSD 1/2ωr dV/dF ωCNT max f (MHz)Superconducting contacts 0 ωRF 480.5 -30dBm min Signal power 320.6 1/3ωr dV/dF max f (MHz) 0 0 ωG ω 1ωJ 2ωJ 3ωJ min ωCNT 320.4 -40 0 40 ΔVG(mV)
  • 23. Mixing with Josephson harmonics -58.2dBmNormal contacts 961.7 ωRF 1ωr V (µV) Signal power f (MHz) 0.4 0 961.1 -43dBm -0.2 ω Could also be ωG 0 a peculiar (perhaps boring) dV/dF ωSD 480.9 1/2ωr ωCNT max non-linearity of the system. f (MHz)Superconducting contacts 0 ωRF 480.5 -30dBm min Signal power 320.6 1/3ωr dV/dF max f (MHz) 0 0 ωG ω 1ωJ 2ωJ 3ωJ min ωCNT 320.4 -40 0 40 ΔVG(mV)
  • 24. Is it Josephson mixing?let’s kill superconductivity.
  • 25. Quench superconductivity: Current bias• Strong bias dependence below Bc Shapiro step range 2.4T 0.6 2.0T above Bc 1.6T below 1.2T 0.8T V(μV) 0.3 0.4T 0T 0 0 20 40 60 I(nA)
  • 26. Quench superconductivity: Temperature • Signal drops 2 orders of magnitude above Tc T(K) R(kΩ) ∆V(nV) 8.5 2.8 100 8 2 7.5 50 1.2 7 0.4 6.5 0 0 50 100 150 t(50‘’ /line)
  • 27. Quench superconductivity: B field 160 1 peaks up peaks down 80 V (nV) 0 -80 5 0 0.6 1.2 1.8 2.4 B(T) 1.8 dV/dI(kΩ) 1 100 B(T) 2 0.9 0 0.00V (nV) I(nA) 0.39 -100 3 0.79 0 250 4 1.18 5 1.57 150 -0.9 6 1.97 2.36 50 7 -1.8 0 959.391 959.4217 959.457 0 0.6 1.2 f(MHz) B (T)
  • 28. Is it a p- junction?? 𝐼 𝑆 = 𝐼 𝐶 sin 𝜑 + 𝜋 = − 𝐼 𝐶 sin 𝜑 +π -• Nothing else (that we can measure) changes sign
  • 29. p- junctions 0-junction π-junctionΨ Ψ x x Emin at φ=0 Emin at φ=0 E E φφ φφ −π π −π I π Zeeman π-junction: when B > BπIs= sin(φ+π) = -sin(φ)
  • 30. p- junctions 0-junction π-junction Zeeman 0-π junctionΨ Ψ Ψ gμB x x x Emin at φ=0 Emin at φ=0 E E↓ E E↑ E εF φφ φφ −π π −π I π gμB Zeeman π-junction: 2∆k k   1  ∆p   ∆p  when B > Bπ Ψ ( x ) ~  exp  i 2 x  h  + exp  − i  h  − x  x   exp    ξ F1 Is= sin(φ+π) = -sin(φ) diffusive junctions: gμBπ = 16ETh=16ħD/L2 (Heikkilla 2000, Yip 2000)
  • 31. 2nd device 50 0-state π-state (?) 0V (nV) -50 Bc=2.85T 1037 -100 0 0.9 1.8 2.7 3.6 B(T) 40 2.22T 2.73T 20 V (nV) 0 -20 1332.7172 1332.912 1333.1068 f (MHz)
  • 32. Is there a smoking gun? let‘s look for the Josephson forceThe Effect of Mechanical Resonance on Josephson Dynamics arXiv:1112.5807
  • 33. Mixing and Josephson force 𝐹 𝐽 = −𝛻𝐸 𝐽 Width of 1st Shapiro stepJosephson force Mixing current Josephson force 0 5 10 � 15 𝑉 20 25 arXiv:1112.5807
  • 34. Extracting mixing current • Measure resonance peak and IV 1 919.018MHz V(uV) ΔI ~10pA 600 0.5 5 ΔV ~50nV V (nV)I(nA) 0 0 520 -0.5 -5 -1 -34 -15 440 P(dBm) 5 30 55 I (a.u.) dV/dI (a.u.) dV (a.u.) dI (a.u.) -40 x x I(nA) 30 0 40 x 4 20 20 x xx 2 10 40 x 0 0 0
  • 35. Josephson force: we don’t see it. dV/dI (a.u.) dV (a.u.) dI (a.u.)T=078mK -40 x x I(nA) 30 0 40 x 4 20 20 x xx 2 10 40 x 0 0 0T=585mK -40 2 3 I(nA) 1.5 1.5 0 2 1 1 0.5 1 0.5 40 0 0T=880mK -40 T=880(5)mK 1.2 2 I(nA) 2 0 0.6 1 1 40 0.2 0 0 -49.71 -46.16 -49.71 -46.16 -49.71 -46.16 P(dBm) P(dBm) P(dBm)
  • 36. Conclusion• In our devices there is strong mixing current that can be attributed to Josephson mixing.• We have found Zeeman π-junction “like” behavior in suspended CNT devices.• Additional phase-sensitive experiments can be interesting to investigate this physics further.• Capacitive drive/detecting schemes can be more important than inductive ones.

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