Nearly quantum limited nanoSQUIDs based on cross-type Nb/AlO<i><sub>x</sub></i>/Nb junctions

Schmelz, M.; Zakosarenko, V.; Schönau, Thomas; Anders, S.; Linzen, S.; Stolz, R.; Meyer, H.‐G.

doi:10.1088/0953-2048/30/1/014001

Cited by 18 publications

(10 citation statements)

References 41 publications

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“…Finally, furthermore improvements will be possible with the adoption of superconducting materials with wider energy-gap, such as lead, niobium and niobium nitride. This will extend the magnetometer working operation at higher temperatures, allowing SQUIPT applications at temperatures accessible with the technology of 4 He cryostats, in order to try to compete with the state of the art nanoSQUID 46 , 47 (flux resolution ).…”

Section: Discussionmentioning

confidence: 99%

High operating temperature in V-based superconducting quantum interference proximity transistors

Ligato

Marchegiani

Virtanen

et al. 2017

Sci Rep

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Here we report the fabrication and characterization of fully superconducting quantum interference proximity transistors (SQUIPTs) based on the implementation of vanadium (V) in the superconducting loop. At low temperature, the devices show high flux-to-voltage (up to 0.52 mV/Φ0) and flux-to-current (above 12 nA/Φ0) transfer functions, with the best estimated flux sensitivity ~ 2.6 μΦ0/(Hz)1/2 reached under fixed voltage bias, where Φ0 is the flux quantum. The interferometers operate up to T bath 2 K, with an improvement of 70% of the maximal operating temperature with respect to early SQUIPTs design. The main features of the V-based SQUIPT are described within a simplified theoretical model. Our results open the way to the realization of SQUIPTs that take advantage of the use of higher-gap superconductors for ultra-sensitive nanoscale applications that operate at temperatures well above 1 K.

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Section: Discussionmentioning

confidence: 99%

High operating temperature in V-based superconducting quantum interference proximity transistors

Ligato

Marchegiani

Virtanen

et al. 2017

Sci Rep

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“…Beyond that, a reduction of the SQUID noise is necessary which could potentially be achieved by utilizing submicrometer Josephson junctions. 20 Apart from the superior noise performance it should be noted that the high bandwidth makes this system well suited for many applications also outside biomagnetism. We intend to use this system, amongst other, for ULF MRI and in particular for the realization of current density imaging and neuronal current imaging.…”

mentioning

confidence: 99%

An ultra-sensitive and wideband magnetometer based on a superconducting quantum interference device

Storm

Hömmen

Drung

2017

Applied Physics Letters

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The magnetic field noise in superconducting quantum interference devices (SQUIDs) used for biomagnetic research such as magnetoencephalography or ultra-low-field nuclear magnetic resonance is usually limited by instrumental dewar noise. We constructed a wideband, ultra-low noise system with a 45 mm diameter superconducting pick-up coil inductively coupled to a current sensor SQUID. Thermal noise in the liquid helium dewar is minimized by using aluminized polyester fabric as superinsulation and aluminum oxide strips as heat shields, respectively. With a magnetometer pick-up coil in the center of the Berlin magnetically shielded room 2 (BMSR2) a noise level of around 150 aT Hz −1/2 is achieved in the white noise regime between about 20 kHz and the system bandwidth of about 2.5 MHz. At lower frequencies, the resolution is limited by magnetic field noise arising from the walls of the shielded room. Modeling the BMSR2 as a closed cube with continuous µ-metal walls we can quantitatively reproduce its measured field noise.Biomagnetism aims at the detection of magnetic fields generated by the human body. As these fields are typically in the range of femtotesla to picotesla when detected outside the human body, high sensitivity magnetometry is required. Traditionally, the preferred detectors are low critical temperature (low-T c ) superconducting quantum interference devices (SQUIDs) operated at liquid helium (LHe) temperatures. Owing to their exquisite sensitivity SQUIDs facilitated the measurements of magnetic fields of the brain, and commercial multichannel systems for magnetoencephalography (MEG) are available with a field noise of about 2 fT Hz −1/2 . SQUID performance is usually limited by the LHe dewar due to Johnson noise in the superinsulation comprised of aluminized foils and the thermal radiation shields made from copper mesh.

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“…The measured white noise level of the nanoSQUIDs is one of the lowest achieved with SQUIDs so far and in this way continues the quest for quantum limited SQUIDs started already several decades ago. 5,11,[24][25][26] Notably, the measured white noise is just a factor four larger than the quantum noise limit given as [h/(2p)ÁL SQ ] 1/2 % 13 nU 0 /Hz 1/2 for this device.…”

mentioning

confidence: 70%

3D nanoSQUID based on tunnel nano-junctions with an energy sensitivity of 1.3 h at 4.2 K

Schmelz

Vettoliere

Zakosarenko³

et al. 2017

Applied Physics Letters

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We report the performance of a reliable three-dimensional nanometer-sized Superconducting QUantum Interference Device (SQUID). The use of superconductor-isolator-superconductor Nb/ Al-AlO x /Nb Josephson tunnel junctions together with small SQUID loop dimensions permits a high modulation depth of the SQUID's critical current and thus leads to very low intrinsic flux noise of the device. In particular, we present electrical characterization including detailed noise investigations. At 4.2 K, two-stage noise measurements with a SQUID as a low noise preamplifier result in a white flux noise of 51 nU 0 /Hz 1/2 , which is equivalent to an energy resolution of 1.3 h, with h being Planck's constant. Simulation of spin sensitivities results in about 1 l B /Hz 1/2 for an electron spin positioned directly above the SQUID ring. Published by AIP Publishing.

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Nearly quantum limited nanoSQUIDs based on cross-type Nb/AlO_x/Nb junctions

Cited by 18 publications

References 41 publications

High operating temperature in V-based superconducting quantum interference proximity transistors

High operating temperature in V-based superconducting quantum interference proximity transistors

An ultra-sensitive and wideband magnetometer based on a superconducting quantum interference device

3D nanoSQUID based on tunnel nano-junctions with an energy sensitivity of 1.3 h at 4.2 K

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Nearly quantum limited nanoSQUIDs based on cross-type Nb/AlOx/Nb junctions

Cited by 18 publications

References 41 publications

High operating temperature in V-based superconducting quantum interference proximity transistors

High operating temperature in V-based superconducting quantum interference proximity transistors

An ultra-sensitive and wideband magnetometer based on a superconducting quantum interference device

3D nanoSQUID based on tunnel nano-junctions with an energy sensitivity of 1.3 h at 4.2 K

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Product

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Nearly quantum limited nanoSQUIDs based on cross-type Nb/AlO_x/Nb junctions