Daniele Torsello

Daniele Torsello
Politecnico di Torino | polito · DISAT - Department of Applied Science and Technology

PhD
I focus mostly on high-frequency superconductivity, HTS, IBS, and particle-irradiation-induced disorder.

About

51
Publications
2,493
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Introduction
My research is focused on the effects of structural disorder on the electromagnetic properties of superconductors both for fundamental and technological studies. The materials are investigated by comparing measurements obtained for the pristine materials and after irradiation. The samples are characterized by a coplanar waveguide resonator technique that yields the London penetration depth, critical temperature and quasiparticle conductivity. One of the open issues concerning iron-based superconductors is whether they are characterized by the s± wave model for the order parameter. To address this issue experimental data is compared to calculations made on the basis of multiband Eliashberg equations.
Additional affiliations
November 2019 - present
Politecnico di Torino
Position
  • Research Associate
Description
  • Study of the electromagnetic properties of Iron based superconductors and their engineering through ion irradiation
November 2016 - October 2019
Politecnico di Torino
Position
  • PhD Student
Description
  • Influence of disorder on the fundamental properties of Iron Based Superconductors
September 2014 - October 2016
Università degli Studi di Torino
Position
  • Master's Student
Description
  • Role of oxygen knock-out in the change of the electrical properties of Bi- 2212 induced by synchrotron radiation nanoprobes
Education
November 2016 - March 2020
Politecnico di Torino
Field of study
  • Physics
September 2014 - October 2016
Università degli Studi di Torino
Field of study
  • theoretical physics
September 2010 - July 2013
Università degli Studi di Milano-Bicocca
Field of study
  • materials science

Publications

Publications (51)
Article
Full-text available
Short hemp fibers, an agricultural waste, were used for producing biochar by pyrolysis at 1000 °C. The so-obtained hemp-derived carbon fibers (HFB) were used as filler for improving the properties of an epoxy resin using a simple casting and curing process. The addition of HFB in the epoxy matrix increases the storage modulus while damping factor i...
Preprint
Full-text available
Niobium is one of the most studied superconductors, both theoretically and experimentally. It is tremendously important for applications, and it has the highest superconducting transition temperature, $T_{c}=9.33$ K, of all pure metals. In addition to power applications in alloys, pure niobium is used for sensitive magneto-sensing, radio-frequency...
Article
The analysis of the radiation damage associated with energetic neutrons is a key factor for the application of glass-ceramics as joining materials in nuclear fusion plants. Triple ion beam irradiation is, currently, the only way to emulate the displacement damage and the effects of transmutation products induced by high energy neutrons at elevated...
Article
Biochar is a novel carbon based material derived from waste that shows promising properties for several applications. In this paper we investigate its potential use as a low cost, greener alternative to commonly used aggregates employed to enhance the neutron shielding performance of concrete. Monte Carlo simulations are performed with the PHITS co...
Article
Full-text available
A microwave technique suitable for investigating the AC magnetic susceptibility of small samples in the GHz frequency range is presented. The method—which is based on the use of a coplanar waveguide resonator, within the resonator perturbation approach—allows one to obtain the absolute value of the complex susceptibility, from which the penetration...
Preprint
Full-text available
We report on the investigation of the magnetic superconductor EuFe$_{2}$(As$_{0.7}$P$_{0.3}$)$_{2}$ based on muon-spin spectroscopy and ac magnetic susceptibility ($\chi$) measurements. The dependence of the internal field at the muon site on temperature is indicative of a ferromagnetic ordering of Eu$^{2+}$ magnetic moments and only the convention...
Article
Full-text available
The 12442 compounds are a recently discovered family of iron-based superconductors, that share several features with the cuprates due to their strongly anisotropic structure, but are so far poorly understood. Here, we report on the gap structure and anisotropy of RbCa 2 (Fe 1− x Ni x ) 4 As 4 F 2 single crystals, investigated by a combination of di...
Preprint
Full-text available
The 12442 compounds are a recently discovered family of iron-based superconductors, that share several features with the cuprates due to their strongly anisotropic structure, but are so far poorly understood. Here, we report on the gap structure and anisotropy of RbCa2(Fe1-xNix)4As4F2 single crystals, investigated by a combination of directional po...
Article
Full-text available
Superconductors are strategic materials for the fabrication of magnetic shields, and within this class, MgB2 has been proven to be a very promising option. However, a successful approach to produce devices with high shielding ability also requires the availability of suitable simulation tools guiding the optimization process. In this paper, we repo...
Article
Full-text available
The development of responsive composite materials is among the most interesting challenges in contemporary material science and technology. Nevertheless, the use of highly expensive nanostructured fillers has slowed down the spread of these smart materials in several key productive sectors. Here, we propose a new piezoresistive PVA composite contai...
Article
The use of superconducting (SC) materials is crucial for shielding quasi-static magnetic fields. However, the frequent requisite of space-saving solutions with high shielding performance requires the development of a 3D modelling procedure capable of predicting the screening properties for different orientations of the applied field. In this paper,...
Chapter
This chapter deals with the effects of disorder on the properties of IBS. Structural disorder enhances charge carriers scattering, affecting the material at the fundamental level, besides yielding to other application-relevant effects, such as vortex pinning. Ion irradiation is one of the most powerful tool to introduce disorder in a controlled way...
Chapter
In this chapter we report on the microwave analysis of the interplay between magnetism and superconductivity—one of the most intriguing topics in condensed matter physics—in single crystals of EuFe2(As1-xPx)2. This material, in a narrow range of composition shows coexisting ferromagnetism and superconductivity, with magnetic ordering at temperature...
Chapter
This chapter deals with a combined experimental and theoretical analysis of the microwave-frequency electromagnetic response of different iron-based superconductor (IBS) families, namely BaFe2As2 with different substitutions (K in the Ba site, Co in the Fe site, and P in the As site) and stochiometric CaKFe4As4. Measurements, performed using a CPWR...
Chapter
In this Chapter we show how we investigated the microwave properties of MgB2 and YBa2Cu3O7-x thin films by the analysis of CPWRs made from the films themselves. Concerning MgB2, the experimental results were interpreted within the framework of a two-band model in the presence of impurity scattering. We also showed that disorder, enhancing interband...
Chapter
In this chapter we provide a brief overview of the main microwave techniques employed for the characterization of superconductors, with a focus on the use of resonant methods. Then, we report on the microwave methods we adopted to obtain the results discussed in the second part of the book, all based on the use of coplanar waveguide resonators (CPW...
Article
Ion irradiation of superconductors allows both the establishment of their radiation hardness and the modification and optimization of their properties useful for applications. In this work, we investigate the effects of proton irradiation with different energies on Fe(Se,Te) thin films grown on CaF<sub>2</sub> and on buffered YSZ substrates. These...
Article
Full-text available
We report on the microwave shielding efficiency of non-structural composites, where inclusions of biochar—a cost effective and eco-friendly material—are dispersed in matrices of interest for building construction. We directly measured the complex permittivity of raw materials and composites, in the frequency range 100 MHz-8 GHz. A proper permittivi...
Article
Full-text available
We investigate the possibility to directly write electrically conducting channels in the desired position in rutile TiO2 devices equipped with asymmetric electrodes - like in memristive devices - by means of the X-ray nanopatterning technique (XNP, i.e. intense, localized irradiation exploiting an X-ray nanobeam). Device characterization is carried...
Article
In this work, multi-functional coatings based on a UV-LED curable epoxy-acrylate resin and different loadings (namely, 1, 2.5, 5 and 10 wt.%) of carbonaceous structures having a peculiar porcupine (PuP)-like morphology were formulated and thoroughly characterized through thermal, dynamic-mechanical and electrical analyses. More specifically, biocha...
Article
Experimental data from the recently discovered iron-based superconductor (IBS) KCa2Fe4As4F2 is analyzed within a realistic five-band s± Eliashberg model with coupling provided by antiferromagnetic spin fluctuations. Fundamental parameters are deduced from available angle resolved photoemission spectoscopy (ARPES) and ab-initio density functional th...
Article
Full-text available
Static (DC) and dynamic (AC, at 14 MHz and 8 GHz) magnetic susceptibilities of single crystals of a ferromagnetic superconductor, EuFe2(As1−xPx)2 (x = 0.23), were measured in pristine state and after different doses of 2.5 MeV electron or 3.5 MeV proton irradiation. The superconducting transition temperature, Tc(H), shows an extraordinarily large d...
Preprint
Full-text available
Static (DC) and dynamic (AC, at 14 MHz and 8 GHz) magnetic susceptibilities of single crystals of a ferromagnetic superconductor, $\textrm{EuFe}_{2}(\textrm{As}_{1-x}\textrm{P}_{x})_{2}$ (x = 0.23), were measured in pristine state and after different doses of 2.5 MeV electron or 3.5 MeV proton irradiation. The superconducting transition temperature...
Article
We report on the effects of thermal treatment of biochar embedded in epoxy-based composites on their microwave electrical properties, linking such properties to the material structure investigated by Raman, X-ray photoelectron spectroscopy, and X-ray diffraction. Annealing temperatures in the range 900-1500°C and biochar concentrations in the epoxy...
Article
Full-text available
We report on ion irradiation experiments performed on compounds belonging to the BaFe2As2 family, each one involving the partial substitution of an atom of the parent compound (K for Ba, Co for Fe, and P for As), with an optimal composition to maximize the superconducting critical temperature Tc. Employed ion beams were 3.5-MeV protons, 250-MeV Au...
Article
X-ray synchrotron sources, possessing high power density, nanometric spot size and short pulse duration, are extending their application frontiers up to the exploration of direct matter modification. In this field, the use of atomistic and continuum models is now becoming fundamental in the simulation of the photoinduced excitation states and event...
Article
Full-text available
We report on the Eliashberg analysis of the electrodynamic response of Ba(Fe1−xRhx)2As2 single crystals across the disorder-induced s± to s++ transition. We previously experimentally identified the transition by its signature in the low temperature value of the penetration depth and observed a peculiar dependency of the critical temperature on diso...
Article
We report on the anisotropy of the London penetration depth of CaKFe4As4, discussing how it relates to its electronic structure and how it modifies under introduction of disorder, both chemically induced (by Ni substitution) and irradiation induced (by 3.5-MeV protons). Indeed, CaKFe4As4 is particularly suitable for the study of fundamental superco...
Article
Full-text available
Irradiation effects are often used to improve the effective pinning in superconductors, but sometimes they can reveal detrimental for superconducting properties. Fe(Se,Te) has been proven to be a very robust material against irradiation, in particular proton irradiation, thus configuring as an ideal material to work in harsh environments such as pa...
Article
Full-text available
We present the characterization and the numerical simulation of a high-temperature superconducting bolometer based on an YBa 2 Cu 3 O 7-x (YBCO) film, which is patterned in serpentine elements and selectively modified by means of micro-collimated high-energy heavy-ion irradiation. The local irradiation of YBCO yields to a controlled reduction of th...
Article
Full-text available
We report on the microwave analysis of the interplay between magnetism and superconductivity in single crystals of EuFe2(As1−xPx)2, accomplished by means of a coplanar waveguide resonator technique. The bulk complex magnetic susceptibility χm extracted through a cavity perturbation approach is demonstrated to be highly sensitive to the magnetic str...
Preprint
Full-text available
We report combined experimental and theoretical analysis of superconductivity in CaK(Fe$_{1-x}$Ni$_x$)$_4$As$_4$ (CaK1144) for $x=$0, 0.017 and 0.034. To obtain the superfluid density, $\rho=\left(1+\Delta \lambda_L(T)/\lambda_L(0) \right)^{-2}$, the temperature dependence of the London penetration depth, $\Delta \lambda_L (T)$, was measured by usi...
Article
We report combined experimental and theoretical analysis of superconductivity in CaK(Fe1−xNix)4As4 (CaK1144) for x=0, 0.017, and 0.034. To obtain the superfluid density ρ=1+ΔλL(T)/λL(0)−2, the temperature dependence of the London penetration depth ΔλL(T) was measured by using a tunnel-diode resonator (TDR) and the results agreed with the microwave...
Article
Most iron-based superconductors are characterized by the s± symmetry of their order parameter, and are expected to go through a transition to the s++ state if enough disorder is introduced. We previously reported the observation of this transition in Ba(Fe1−xRhx)2As2 through a study of the disorder dependence of the critical temperature and low-tem...
Preprint
Most iron-based superconductors are characterized by the s+- symmetry of their order parameter, and are expected to go through a transition to the s++ state if enough disorder is introduced. We previously reported the observation of this transition in Ba(Fe1-xRhx)2As2 through a study of the disorder dependence of the critical temperature and low-te...
Article
Full-text available
We report on the combined experimental and theoretical analysis of the microwave-frequency electromagnetic response of BaFe2As2 single crystals with different substitutions: K in the Ba site (hole doping), Co in the Fe site (electron doping), and P in the As site (isovalent substitution). Measurements using a coplanar resonator technique lead to th...
Article
At the present day, iron-based superconductors (IBS) can be considered as competitors of cuprates for the fabrication of su-perconducting cables for high field application in the presence of particle irradiation. In particular, it has been demonstrated that 11 IBS are very robust against proton irradiation. In this work, we analyze the effect of th...
Article
We report on a combined experimental and modelling approach towards the design and fabrication of efficient bulk shields for low-frequency magnetic fields. To this aim, MgB 2 is a promising material when its growing technique allows the fabrication of suitably shaped products and a realistic numerical modelling can be exploited to guide the shield...
Article
Full-text available
Microwave measurements of the London penetration depth and critical temperature Tc were used to show evidence of a disordered-driven transition from s± to s++ order parameter symmetry in optimally doped Ba(Fe1−xRhx)2As2 single crystals, where disorder was induced by means of 3.5 MeV proton irradiation. Signatures of such a transition, as theoretica...
Article
The electrodynamic response of Ba1-xKxFe2As2 single crystals at the microwave frequencies has been investigated by means of a coplanar resonator technique, at different values of non-magnetic disorder introduced into the samples by heavy-ion irradiation. The surface impedance Z s = R s + iX s conforms to the classical skin effect above the critical...
Article
We investigate the microscopic mechanism responsible for the change of macroscopic electrical properties of the Bi2Sr2CaCu2O8+δ high-temperature superconductor induced by intense synchrotron hard x-ray beams. The possible effects of secondary electrons on the oxygen content via the knock-on interaction are studied by Monte Carlo simulations. The ch...
Article
Full-text available
In this paper we explore the effects of 3.5 MeV proton irradiation on Fe(Se,Te) thin films grown on CaF2. In particular, we carry out a systematic experimental investigation with different irradiation fluences up to 7.30x10^16 cm^-2 and different proton implantation depths, in order to clarify whether and to what extent the critical current is enha...
Article
Full-text available
One of the open issues concerning iron-based superconductors is whether the s± wave model is able to account for the overall effects of impurity scattering, including the low rate of decrease of the critical temperature with the impurity concentration. Here we investigate Ba1−xKxFe2As2 crystals where disorder is introduced by Au-ion irradiation. Cr...

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Project
Superconductivity is a fascinating phenomenon that still eludes a comprehensive understanding, leaving room for new experiments and analysis. New materials and approaches for obtaining superconductivity are continuously being discovered, fuelling the need for fundamental investigations and theoretical studies. daniele.torsello@polito.it Deadline for manuscript submissions: 20 May 2023 mdpi.com/si/138817 Moreover, some materials are now technologically mature or close to becoming so, opening the way to paradigm shi s in several fields ranging from quantum computing and sensing to nuclear fusion technology. This Special Issue, therefore, aims to provide a space for theoretical and experimental studies in superconducting materials, as well as reports on technological advances based on exploiting superconductivity. Full articles, short communications, and review papers are welcome for submission at the link: https://www.mdpi.com/journal/materials/special_issues/OT63640BAK