arXiv subjects

G. De Luca

Publications and source records attributed to G. De Luca.

5 recordsLinked to original sources

arXiv2026

Spin-to-charge-current conversion in altermagnetic candidate RuO$_2$ probed by terahertz emission spectroscopy

Using the THz emission spectroscopy, we investigate ultrafast spin-to-charge current conversion in epitaxial thin films of the altermagnetic candidate RuO$_2$. We perform a quantitative analysis of competing effects that can contribute to the measured anisotropic THz emission. These include the anisotropic inverse spin splitter and spin Hall effects in RuO$_2$, the anisotropic conductivity of RuO$_2$, and the birefringence of the TiO$_2$ substrate. We observe that the leading contribution to the measured signals comes from the anisotropic inverse spin Hall effect, with an average spin-Hall angle of $2.4\times 10^{-3}$ at room temperature. In comparison, a possible contribution from the altermagnetic inverse spin-splitter effect is found to be approximately $2-4\times 10^{-4}$. Our work stresses the importance of carefully disentangling spin-dependent phenomena that can be generated by the unconventional altermagnetic order, from the effects of the relativistic spin-orbit coupling.

cond-mat.mes-hall↗

arXiv2024

The environmental low-frequency background for macro-calorimeters at the millikelvin scale

Many of the most sensitive physics experiments searching for rare events, like neutrinoless double beta ($0νββ$) decay and dark matter interactions, rely on cryogenic macro-calorimeters operating at the mK-scale. Located underground at the Gran Sasso National Laboratory (LNGS), in central Italy, CUORE (Cryogenic Underground Observatory for Rare Events) is one of the leading experiments for the search of $0νββ$ decay, implementing the low-temperature calorimetric technology. We present a novel multi-detector analysis to correlate environmental phenomena with the low-frequency noise of low-temperature calorimeters. Indeed, the correlation of marine and seismic data with data from a pair of CUORE detectors indicates that cryogenic detectors are sensitive not only to intense vibrations generated by earthquakes, but also to the much fainter vibrations induced by marine microseisms in the Mediterranean Sea due to the motion of sea waves. Proving that cryogenic macro-calorimeters are sensitive to such environmental sources of noise opens the possibility of studying their impact on the detectors physics-case sensitivity. Moreover, this study could pave the road for technology developments dedicated to the mitigation of the noise induced by marine microseisms, from which the entire community of cryogenic calorimeters can benefit.

physics.ins-det↗

arXiv2024

Strain-Tuned Magnetic Frustration in a Square Lattice $J_1$-$J_2$ Material

Magnetic frustration is a route that can lead to the emergence of novel ground states, including spin liquids and spin ices. Such frustration can be introduced through either the geometry of lattice structures or by incompatible exchange interactions. Identifying suitable strategies to control the degree of magnetic frustration in real systems is an active field of research. In this study, we devise a design principle for the tuning of frustrated magnetism on the square lattice through the manipulation of nearest (NN) and next-nearest neighbor (NNN) antiferromagnetic (AF) exchange interactions. By studying the magnon excitations in epitaxially-strained La$_2$NiO$_4$ films using resonant inelastic x-ray scattering (RIXS) we show that, in contrast to the cuprates, the dispersion peaks at the AF zone boundary. This indicates the presence of an AF-NNN spin interaction. Using first principles simulations and an effective spin-model, we demonstrate the AF-NNN coupling to be a consequence of the two-orbital nature of La$_2$NiO$_4$. Our results demonstrate that compressive strain can enhance this coupling, providing a design principle for the tunability of frustrated magnetism on a square lattice.

cond-mat.str-el↗

arXiv2021

Robust ferromagnetism in insulating La$_2$NiMnO$_6$ thin films

The field of oxide spintronics can strongly benefit from the establishment of robust ferromagnetic insulators with near room-temperature Curie temperature. Here we investigate the structural, electronic, and magnetic properties of atomically-precise epitaxially-strained thin films of the double perovskite La$_2$NiMnO$_6$ (LNMO) grown by off-axis radio-frequency magnetron sputtering. We find that the films retain both a strong insulating behavior and a bulk-like Curie temperature in the order of 280 K, nearly independently from epitaxial strain conditions. These results suggest a prospective implementation of LNMO films in multi-layer device architectures where a high-temperature ferromagnetic insulating state is a prerequisite.

cond-mat.mtrl-sci↗

arXiv2016

First Results of GINGERino, a deep underground ringlaser

Large ring-laser gyroscopes are capable of measuring angular rotations with a precision well below fractions of $prad/s$, not far from $10^{-14}$ $rad/s$, the accuracy required for General Relativity tests, this is what the GINGER (Gyroscope-IN-GEneral-Relativity) experiment is aiming for. These features do not guarantee the possibility of measuring the General Relativity Lense--Thirring effect, that manifests itself as a tiny ($\approx 10^{-9} \times Ω_E$) perturbation of the Earth rotation rate. An underground location being in principle less affected by external local disturbances represents a good candidate for housing such a challenging experiment. GINGERino is a test apparatus to investigate the residual local disturbances in the most inner part of the underground international laboratory of the GranSasso (LNGS). It consists of a square ring laser with a $3.6$ m side. The instrument has been tailored to be the larger allowed by the particular location inside the laboratory. Its main objective is to measure the very low frequency rotational motions, in order to prove that LNGS is a suitable location for very low noise measurements and, possibly, General Relativity tests. Aside this main goal, GINGERino will provide unique data for geodesy and geophysics. Its installation has been completed during 2015. Since then, several long set of data have been collected, and the apparatus has been continuously running unattended for more than one week. The typical power spectrum sensitivity was a few $ 10^{-10} rad/s/\sqrt(Hz)$, with integration time not longer than tens of seconds. Improvements of the apparatus are ongoing in order to improve the integration time.

physics.ins-det↗