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We report on the effects of visible light on the low temperature electronic properties of the spin-polarized two dimensional electron system (2DES) formed at the interfaces between LaAlO 3 , EuTiO 3 and (001) SrTiO 3 . A strong, persistent modulation of both longitudinal and transverse conductivity was obtained using light emitting diodes (LEDs) with emissions at different wavelengths in the visible spectrum range. In particular, Hall effect data show that visible light induces a non-volatile electron filling of bands with mainly 3d x z , y z character, and at the same time an enhancement of the anomalous Hall effect associated to the magnetic properties of the system. Accordingly, a suppression of the weak-anti localization corrections to the magneto-conductance is found, which correlates with an enhancement of the spin-polarization and of the ferromagnetic character of 2DES. The results establish the LED-induced photo-doping as a viable route for the control of the ground state properties of artificial spin-polarized oxide 2DES.

The versatility of properties displayed by two‐dimensional electron gases (2DEGs) at oxide interfaces has fostered intense research in hope of achieving exotic electromagnetic effects in confined systems. Of particular interest is the recently discovered superconducting state appearing in (111)‐oriented KTaO3 interfaces, with a critical temperature Tc≈2 K, almost 10 times higher than that of SrTiO3‐based 2DEGs. Just as in SrTiO3‐based 2DEGs, fabricating devices in this new system is a technical challenge due to the fragility of the 2DEG and the propensity of bulk KTaO3 to become conducting outside the devices upon adventitious oxygen vacancy doping. Here, three different techniques are presented for patterning Hall bars in AlOx/KTaO3 (111) heterostructures. The devices show superconducting transitions ranging from 1.3 to 1.78 K, with limited degradation from the unpatterned thin film, and enable an efficient tuning of the carrier density by electric field effect. The array of techniques allows for the definition of channels with a large range of dimensions for the design of various kinds of devices to explore the properties of this system down to the nanoscale.

Multiferroics are compounds in which at least two ferroic orders coexist, typically ferroelectricity and some form of magnetism. While magnetic order can arise in both insulating and metallic compounds, ferroelectricity is in principle only allowed in insulators, although ferroelectric metals have been proposed and several two-dimensional systems have been reported to behave in this way. However, their combination with and coupling to magnetic order have not been realized thus far. Here we show the coexistence of ferroelectricity and magnetism in an oxide-based two-dimensional electron gas. We report a modulation of the Ti–O polar displacements depending on the ferroelectric polarization direction, and a voltage-induced hysteresis of the sheet resistance that is reminiscent of the ferroelectric polarization loop. The transport properties of the electron gas display an anomalous Hall effect and magnetoresistance that can both be modulated and cycled by switching the remanent polarization, demonstrating a magnetoelectric coupling. Our findings provide new opportunities in quantum matter that stem from the interplay between ferroelectricity, ferromagnetism, metallicity and Rashba spin–orbit coupling.Materials that simultaneously display ferroelectricity and magnetism, and are metallic, are very rare. Now, the two-dimensional electron gas in an oxide heterostructure brings all of this behaviour together.

The insertion of a few unit-cell-thick EuTiO 3 layers at the interface between LaAlO 3 and SrTiO 3 leads to the formation of an electric-field-tunable quasi-two-dimensional electron system where ferromagnetism and superconductivity coexist. Advances in growth technology of oxide materials allow single atomic layer control of heterostructures. In particular delta doping, a key materials’ engineering tool in today’s semiconductor technology, is now also available for oxides. Here we show that a fully electric-field-tunable spin-polarized and superconducting quasi-2D electron system (q2DES) can be artificially created by inserting a few unit cells of delta doping EuTiO 3 at the interface between LaAlO 3 and SrTiO 3 oxides 1 , 2 . Spin polarization emerges below the ferromagnetic transition temperature of the EuTiO 3 layer ( T FM = 6–8 K) and is due to the exchange interaction between the magnetic moments of Eu-4 f and of Ti-3 d electrons. Moreover, in a large region of the phase diagram, superconductivity sets in from a ferromagnetic normal state. The occurrence of magnetic interactions, superconductivity and spin–orbit coupling in the same q2DES makes the LaAlO 3 /EuTiO 3 /SrTiO 3 system an intriguing platform for the emergence of novel quantum phases in low-dimensional materials.

High-resolution focused ion beam lithography has been used to fabricate YBa2Cu3O7-x (YBCO) wires with nanometric lateral dimensions. In the present work, we investigate Flux-flow instabilities in nanowires of different widths, showing sudden voltage switching jumps from the superconducting to the normal state. We present an extensive study on the temperature and field dependence of the switching characteristics which reveal that voltage jumps become less abrupt as the temperature increases, and disappear at the vortex-liquid state. On the contrary, the current distribution at the critical point becomes narrower at high temperatures. Sharp voltage switchings very close to the critical current density can be obtained by reducing the width of the nanowires, making them very appealing for practical applications.

The versatility of properties displayed by two‐dimensional electron gases (2DEGs) at oxide interfaces has fostered intense research in hope of achieving exotic electromagnetic effects in confined systems. Of particular interest is the recently discovered superconducting state appearing in (111)‐oriented KTaO 3 interfaces, with a critical temperature T c ≈2 K, almost 10 times higher than that of SrTiO 3 ‐based 2DEGs. Just as in SrTiO 3 ‐based 2DEGs, fabricating devices in this new system is a technical challenge due to the fragility of the 2DEG and the propensity of bulk KTaO 3 to become conducting outside the devices upon adventitious oxygen vacancy doping. Here, three different techniques are presented for patterning Hall bars in AlO x /KTaO 3  (111) heterostructures. The devices show superconducting transitions ranging from 1.3  to 1.78 K, with limited degradation from the unpatterned thin film, and enable an efficient tuning of the carrier density by electric field effect. The array of techniques allows for the definition of channels with a large range of dimensions for the design of various kinds of devices to explore the properties of this system down to the nanoscale.

We describe the behavior of a beam balance used for the measurement of small forces, in macroscopic samples, in tens of mHz frequency band. The balance, which works at room temperature, is the prototype of the cryogenic balance of the Archimedes experiment, aimed at measuring the interaction between electromagnetic vacuum fluctuations and the gravitational field. The balance described has a 50-cm aluminum arm and suspends an aluminum sample of 0.2 Kg and a lead counterweight. The read-out is interferometric, and the balance works in closed loop. It is installed in the low seismic noise laboratory of SAR-GRAV (Sardinia—Italy). Thanks to the low sensing and actuation noise and finally thanks to the low environmental noise, the sensitivity in torque τ n ~ is about τ n ~ ≈ 2 ∗ 10 - 12 Nm / Hz at 10 mHz and reaches a minimum of about τ n ~ ≈ 7 ∗ 10 - 13 Nm / Hz at tens of mHz, corresponding to the force sensitivity F n ~ of F n ~ ≈ 3 ∗ 10 - 12 N/ Hz . The achievement of this sensitivity, which turns out to be compatible with thermal noise estimation, on the one hand, demonstrates the correctness of the optical and mechanical design and on the other paves the way to the completion of the final balance. Furthermore, since the balance is equipped with weight and counterweight made of different materials, it is sensitive to the interaction with dark B-L photons. A first very short run made to evaluate constraints on B-L dark photon coupling shows encouraging results that will be discussed in view of next future scientific runs.

In this paper we study the Casimir energy of a sample made by N cavities, with N ≫ 1 , across the transition from the metallic to the superconducting phase of the constituting plates. After having characterised the energy for the configuration in which the layers constituting the cavities are made by dielectric and for the configuration in which the layers are made by plasma sheets, we concentrate our analysis on the latter. It represents the final step towards the macroscopical characterisation of a “multi-cavity” (with N large) necessary to fully understand the behaviour of the Casimir energy of a YBCO (or a GdBCO) sample across the transition. Our analysis is especially useful to the Archimedes experiment, aimed at measuring the interaction of the electromagnetic vacuum energy with a gravitational field. To this purpose, we aim at modulating the Casimir energy of a layered structure, the multi-cavity, by inducing a transition from the metallic to the superconducting phase. After having characterised the Casimir energy of such a structure for both the metallic and the superconducting phase, we give an estimate of the modulation of the energy across the transition.

High-resolution focused ion beam lithography has been used to fabricate YBa₂Cu₃O (YBCO) wires with nanometric lateral dimensions. In the present work, we investigate Flux-flow instabilities in nanowires of different widths, showing sudden voltage switching jumps from the superconducting to the normal state. We present an extensive study on the temperature and field dependence of the switching characteristics which reveal that voltage jumps become less abrupt as the temperature increases, and disappear at the vortex-liquid state. On the contrary, the current distribution at the critical point becomes narrower at high temperatures. Sharp voltage switchings very close to the critical current density can be obtained by reducing the width of the nanowires, making them very appealing for practical applications.

We report the tilt sensitivity reached by the ARCHIMEDES tiltmeter in the 2–20 Hz frequency region, where seismic noise is expected to give an important limitation to the sensitivity in the next future Gravitational Waves detection, particularly through Newtonian noise. The tilt noise level θ ~ ( f ) is about 10 - 12 rad / Hz in most of the band, reaching the minimum of θ ~ = 7 · 10 - 13 rad / Hz around 9 Hz. The tiltmeter is a beam balance with a 0.5 m suspended arm and interferometric optical readout, working in closed loop. The results have been obtained by a direct measurement of the ground tilt at the Sos Enattos site (Sardinia, Italy). This sensitivity is a requirement to use the tiltmeter as part of an effective Newtonian noise reduction system for present Gravitational Waves detectors, and also confirms that Sos Enattos is among the quietest sites in the world, suitable to host the third-generation Gravitational Waves detector Einstein Telescope.