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Sergey Frolov Vincent Mourik Ilse van Weperen Kun Zuo Erik Bakkers, Sebastien Plissard (TU/e &TUD)
Carlo Beenakker, Anton Akmerov, Fabian Hassler, Yuli Nazarov (Leiden & Delft)
Stevan Nadj-Perge Vlad Pribiag Johan van den Berg
NanoWire Team: spin-orbit qubits and Majorana Fermions
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InSb Zinc Blende nanowires; length ~ 2-3 µm, diameter 80-120 nm
InSb
InAs stem
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normal, Au contacts
Characterization by spin-orbit qubits experiments
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Characterization using qubit techniques
few-electron quantum dots
spin-orbit level repulsion
electron spin resonance
source drain
gates
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Quantitative numbers for Rashba spin orbit strength in InSb nanowires
Eso =2
2mλso2
λso = 200nm;Eso = 50µeV
α =2
mλso= 0.02eV ⋅nm
Eso
E BSO
k
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n p n
Bia
s (m
V)
VPL(mV)
0
50
100
-50
-100
-500 -1000 -1500
gap 1h 2h 3h
d)
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-1100 -1200 -1300 -1400
-700
-8
00
-900
VLG
(m
V)
VRG (mV)
-100
0
-1500
n p p n
a)
b)
(1,1)
(0,0)
(0,1)
(1,0) (2,0)
(0,2)
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Freq
uenc
y (G
Hz)
2.5
7.5
12.5
B (mT)
-300 0 -300
I (pA
)
1.0
0
a)
b)
c)
Holes: interesting alternative for spin-qubits and Major.anas
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B
67⁰
Contact spacing = 250 nm
InSb wire Ti/NbTiN contact (10/100 nm) Global backgate
Next: superconducting contacts
NbTiN technology from Klapwijk group
Rn = 1.4 kΩ
similar data from Marcus group on InAs wires and Xu group on InSb wires.
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Supercurrents through InSb nanowires
NbTiN contacts, back gate only
Supercurrent!
I (n
A)
-2
2
I (n
A)
-2
2
I (n
A)
-1
1
Vgate (V) 20 60
B (T) 0 1 B (T) 0 0.4
nw B nw B
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Induced superconducting gap: Δ* ≈ 700 µV @ B = 0 T
4Δ*
co-tunneling spectroscopy
yellow line: EZ =±gµBB
region between 0.3 and 0.5 T with: EZ > Δ*
=> requirement for a topological superconductor
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Majorana’s using nanowires; papers from 2010
• Majorana Fermions and a Topological Phase Transition in Semiconductor-Superconductor Heterostructures Roman M. Lutchyn, Jay D. Sau, S. Das Sarma
• Helical liquids and Majorana bound states in quantum wires
Yuval Oreg, Gil Refael, Felix von Oppen • Tunneling characteristic of a chain of Majorana bound states
Karsten Flensberg • Majorana fermions in multiband semiconducting nanowires
Roman M. Lutchyn, Tudor Stanescu, S. Das Sarma • Quantized conductance at the Majorana phase transition in a disordered superconducting wire
A.R. Akhmerov, J.P. Dahlhaus, F. Hassler, M. Wimmer, C.W.J. Beenakker • Anyonic interferometry without anyons: How a flux qubit can read out a topological qubit
F. Hassler, A. R. Akhmerov, C.-Y. Hou, C. W. J. Beenakker • Non-Abelian statistics and topological quantum information processing in 1D wire networks
Jason Alicea, Yuval Oreg, Gil Refael, Felix von Oppen, Matthew P. A. Fisher • Topological quantum buses: coherent quantum information transfer between topological and conventional qubits
Parsa Bonderson, Roman M. Lutchyn • Interface Between Topological and Superconducting Qubits
Liang Jiang, Charles L. Kane, John Preskill
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First set of experiments
van Dam, Nature 2006
• tunneling – zero bias peak
• topologically protected quantized conductance
• 4π periodicity in Majorana SQUID: I = Ic sin(φ/2)
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Other zero-bias peaks
Van Wees et al., PRL 69, 510 (1992) Marmorkos, Beenakker and Jalabert, PRB 48, 2811(1993)
Reflectonless tunneling ⇒ peak at zero bias; around B = 0 up to one fluxquantum in area
Kondo effect ⇒ peak at zero bias; splits with Zeeman energy
“Nazarov peaks” ⇒ peak at zero bias; don’t stick to zero and move with B-field.
“Brouwer peaks” ⇒ Fermionic peaks at very low energy: move with B.
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peaks come and go, but never stick to zero-bias
when changing B at B ≠ 0