
Key Equipment
QNS is operating three ESR-STM systems that are equipped: a) with high-frequency equipment, b) operate at low temperature, and c) in vector magnetic fields.
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• One commercial tool, nicknamed Alice, operates at 0.4 K for almost two days, after which the cooling fluids need to be replenished, which causes a downtime of about 5 hours.
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• A second system, which is home built and nicknamed Bob, uses a dilution refrigerator and is able to continuously operate at temperatures as low as 30 mK.
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• Our third ESR-STM system, nicknamed Eve, is fully home built which gives us the most flexibility to incorporate novel upgrades. It operates in continuous circulation at 1.2 K.
ALICE ESR-STM System
Commercial system
Received: December 2018
First Results: February 2019
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Key results
• First ever ESR-STM on a molecule
• Pulsed ESR-STM
• ESR double resonance on two spins
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Specifications
Temp: 0.4 K in single shot mode
1.8 K in continuous mode
Magnet: 6 T perpendicular to sample
5 T in plane
2 T vector field in any angle
ESR: Best range: 10-20 GHz

BOB ESR-STM System
Partially home-built system
Start of assembly: August 2019
First Results: March 2020
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Key results
• ESR as a function of magnetic field angle
• Spins on superconductor spectroscopy
• ESR double resonance on two spins
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Specifications
Temp: 0.01 K in continuous mode
Higher temperatures are possible
Magnet: 6 T perpendicular to sample
9 T in plane
3 T vector field at any angle
ESR: Best range: DC-35 GHz (Tip & Antenna)

EVE ESR-STM System
Fully home-built system
Start of assembly: September 2019
First Results: August 2021
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Key results
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ESR at variable temperatures (up to 10 K)
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ESR sensor attached to the STM tip
Specifications
Temp: 1.3 K in continuous mode with He-4
1.1 K in single-shot mode with He-4
Lower temperature with He-3 planned
Magnet: 4 T perpendicular to sample
6 T in plane
4 T vector field at any angle
ESR: Up to 40 GHz with antenna
ESR on tip OR on antenna

CHARLIE ESR-STM System
Fully home-built system
Start of assembly: May 2021
First Results: October 2022
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Key results
• World best vibration noise level: 20 fA/sqrt(Hz) @ 10 mV, 1 nA (Tunneling condition)
​• Measurement of Landau-Zener transition gap in picoelectron-volts
Specifications
Temp: 1.1 K in continuous mode with He-4
0.99 K in single-shot mode with He-4
Lower temperature with He-3 planned
Magnet: 0.25 T (0.1 T/s) perpendicular to sample
1 T (0.5 T/s) in-plane
ESR: Up to 30 GHz 3 RF cables
