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Register a new userOn-chip SQUID measurements in the presence of high magnetic fields
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We report a low temperature measurement technique and magnetization data of a quantum molecular spin, by implementing an on-chip SQUID technique. This technique enables the SQUID magnetometery in high magnetic fields, up to 7 Tesla. The main challenges and the calibration process are detailed. The measurement protocol is used to observe quantum tunneling jumps of the S=10 molecular magnet, Mn12-tBuAc. The effect of transverse field on the tunneling splitting for this molecular system is addressed as well.
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We report development and microwave characterization of rf SQUID (Superconducting QUantum Interference Device) qubits, consisting of an aluminium-based Josephson junction embedded in a superconducting loop patterned from a thin film of TiN with high kinetic inductance. Here we demonstrate that the systems can offer small physical size, high anharmonicity, and small scatter of device parameters. The hybrid devices can be utilized as tools to shed further light onto the origin of film dissipation and decoherence in phase-slip nanowire qubits, patterned entirely from disordered superconducting films.
Scanning nanoscale superconducting quantum interference devices (SQUIDs) are gaining interest as highly sensitive microscopic magnetic and thermal characterization tools of quantum and topological states of matter and devices. Here we introduce a novel technique of collimated differential-pressure magnetron sputtering for versatile self aligned fabrication of SQUID on tip (SOT) nanodevices, which cannot be produced by conventional sputtering methods due to their diffusive, rather than the required directional point-source, deposition. The new technique provides access to a broad range of superconducting materials and alloys beyond the elemental superconductors employed in the existing thermal deposition methods, opening the route to greatly enhanced SOT characteristics and functionalities. Utilizing this method, we have developed MoRe SOT devices with sub-50 nm diameter, magnetic flux sensitivity of 1.2 $muPhi_0/Hz^{1/2}$ up to 3 T at 4.2 K, and thermal sensitivity better than 4 $mu K/Hz^{1/2}$ up to 5 T, about five times higher than any previous report, paving the way to nanoscale imaging of magnetic and spintronic phenomena and of dissipation mechanisms in previously inaccessible quantum states of matter.
Spectroscopy is a powerful tool to probe physical, chemical, and biological systems. Recent advances in microfabrication have introduced novel, intriguing mesoscopic quantum systems including superconductor-semiconductor hybrid devices and topologically non-trivial electric circuits. A sensitive, general purpose spectrometer to probe the energy levels of these systems is lacking. We propose an on-chip absorption spectrometer functioning well into the millimeter wave band which is based on a voltage-biased superconducting quantum interference device. We demonstrate the capabilities of the spectrometer by coupling it to a variety of superconducting systems, probing phenomena such as quasiparticle and plasma excitations. We perform spectroscopy of a microscopic tunable non-linear resonator in the 40-50 GHz range and measure transitions to highly excited states. The Josephson junction spectrometer, with unprecedented frequency range, sensitivity, and coupling strength will enable new experiments in linear and non-linear spectroscopy of novel mesoscopic systems.
Scanning superconducting quantum interference device (SQUID) microscopy is a magnetic imaging technique combining high-field sensitivity with nanometer-scale spatial resolution. State-of-the-art SQUID-on-tip probes are now playing an important role in mapping correlation phenomena, such as superconductivity and magnetism, which have recently been observed in two-dimensional van der Waals materials. Here, we demonstrate a scanning probe that combines the magnetic and thermal imaging provided by an on-tip SQUID with the tip-sample distance control and topographic contrast of a non-contact atomic force microscope (AFM). We pattern the nanometer-scale SQUID, including its weak-link Josephson junctions, via focused ion beam milling at the apex of a cantilever coated with Nb, yielding a sensor with an effective diameter of 365 nm, field sensitivity of 9.5 $text{nT}/sqrt{text{Hz}}$ and thermal sensitivity of 620 $text{nK}/sqrt{text{Hz}}$, operating in magnetic fields up to 1.0 T. The resulting SQUID-on-lever is a robust AFM-like scanning probe that expands the reach of sensitive nanometer-scale magnetic and thermal imaging beyond what is currently possible.
We designed and fabricated a new type of superconducting quantum interference device (SQUID) susceptometers for magnetic imaging of quantum materials. The 2-junction SQUID sensors employ 3D Nb nano-bridges fabricated using electron beam lithography. The two counter-wound balanced pickup loops of the SQUID enable gradiometric measurement and they are surrounded by a one-turn field coil for susceptibility measurements. The smallest pickup loop of the SQUIDs were 1 ${mu}m$ in diameter and the flux noise was around 1 $mu{Phi}_0/sqrt{Hz}$ at 100 Hz. We demonstrate scanning magnetometry, susceptometry and current magnetometry on some test samples using these nano-SQUIDs.
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