Optimal Quantum Key Distribution Networks in npj Quantum information

ISC researchers C. Castellano, V.Brosco and L. Pilozzi coauthored an interesting work published in npj quantum information.

Optimal quantum key distribution networks: capacitance versus security

L. Cirigliano, V.Brosco, C. Castellano, C. Conti, L. Pilozzi,  npj Quantum Information 10, 44 (2024)

Abstract

The rate and security of quantum communications between users placed at arbitrary points of a quantum communication network depend on the structure of the network, on its extension and on the nature of the communication channels.

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Superconducting Qubit Based on Twisted Cuprate Van der Waals Heterostructures in Physical Review Letters

ISC researcher Valentina Brosco coauthored an interesting research proposing a novel superconduting qubit desigm. The work has been selected for an Editor’s Suggestion in Physical Review Letters, see Superconducting Qubit Based on Twisted Cuprate Van der Waals Heterostructures V. Brosco, G. Serpico, V. Vinokur, N. Poccia and U. Vool, Phys. Rev. Lett. 132, 017003 (2024).

Abstract

Van-der-Waals assembly enables the fabrication of novel Josephson junctions featuring an atomically sharp interface between two exfoliated and relatively twisted Bi2Sr2CaCu2O8+x (Bi2212) flakes.

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Enhanced Critical Field at an Oxide Interface in Nano Letters

Almost uncharged and non-magnetic electrons explain resilience to magnetic fields in exotic superconductors

ISC Director, J. Lorenzana, coauthored an interesting work on Nano Letters, Enhanced Critical Field of Superconductivity  at an Oxide Interface, Athby H. Al-Tawhid
A. H. Al-Tawhid, S. J. Poage, S. Salmani-Rezaie, A. Gonzalez, S. Chikara, D. A. Muller, D. P. Kumah, Maria N. Gastiasoro, J. Lorenzana, and K.… Read the rest

2D High-Temperature Superconductor Integration in Contact Printed Circuit Boards in ACS Applied Materials and Interfaces

ISC researcher Valentina Brosco coauthored an interesting research article published in ACS Applied Materials and Interfaces, C. Saggau et al.2D High-Temperature integration in Contact Printed Circuit Boards, ACS Appl. Mater. Interfaces 44, 51558 (2023).  The work paves the way to the realization of novel  printed circuits and devices integrating atomically thin high-Tc superconducting  films.

2D High-Temperature Superconductor Integration in Contact Printed Circuit Boards

Inherent properties of superconducting Bi2Sr2CaCu2O8+x films, such as the high superconducting transition temperature Tc, efficient Josephson coupling between neighboring CuO layers, and fast quasiparticle relaxation dynamics, make them a promising platform for advances in quantum computing and communication technologies.

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Waveguide QED with Quadratic Light-Matter Interactions – PRX Quantum

ISC researcher S. Felicetti is the lead author of a research article now published in PRX Quantum, in collaboration with Aalto University (Helsinki) and the Institute of Fundamental Physics IFF-CSIC (Madrid): U. Alushi, T. Ramos, J.-J. G.-Ripoll, R. Di Candia, and S. Felicetti PRX Quantum 4, 030326 (2023).

Quadratic light-matter interactions are nonlinear couplings such that quantum emitters interact with photonic or phononic modes exclusively via the exchange of excitation pairs.… Read the rest

Mechanism for fluctuating pair density wave in Nature Communications

ISC researcher L. Fanfarillo coauthored an interesting article now published in Nature Communications, C. Setty, L. Fanfarillo and P. J. Hirschfeld Nat. Comm.  3181 (2023).

In weakly coupled BCS superconductors, only electrons within a tiny energy window around the Fermi energy, EF, form Cooper pairs. This may not be the case in strong coupling superconductors such as cuprates, FeSe, SrTiO3 or cold atom condensates where the pairing scale, EB, becomes comparable or even larger than EF.

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Heat flow on the nanoscale in La Rivista del Nuovo Cimento (2023)

ISC researcher Stefano Lepri and ISC associate Roberto Livi coauthored an interesting review article  showing how heat flow is different on the nanoscale.

G. Benenti, D. Donadio, S. Lepri and R. Livi, Non Fourier heat transport in nanosystems, La Rivista del Nuovo Cimento (2023)

Energy transfer in small nano-sized systems can be very different from that in their macroscopic counterparts due to reduced dimensionality, interaction with surfaces, disorder, and large fluctuations.

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Ionic liquids: a spectroscopic investigation

Ionic liquids (IL) are salts formed by organic cations, like imidazolium, pyrrolidinium, ammonium or alkyl phosphonium, and organic/inorganic anions, like hexafluorophosphate, tetrafluoroborate, triflate, dicyanamide, tetracyanamethanide or bis(trifluoromethanesulfonyl)imide (TFSI). The presence of such bulky and asymmetric ions decreases the ion-ion interactions and lowers the melting point with respect to more classical salts, reaching values as low as -20°C.

ILs posses many peculiar properties, such as an extremely low vapor pressure, a high ionic conductivity, a high thermal, chemical and electrochemical stability, a high thermal capacity and a good solvent capability.… Read the rest

Solid state hydrogen storage

Hydrogen is attracting renewed interest as an energy carrier, due to the necessity of finding ecological energy media which may decrease the environmental pollution from fossil fuels. Hydrogen storage represents a nodal point for the development of a hydrogen economy.

Of the three possible ways to store hydrogen, i.e. as high pressure gas, as a liquid (~20 K at atmospheric pressure), or as hydrides in solids, the latter one appears as the most promising, due to the high mass and volume density and safety.… Read the rest

Volume collapse transition in Ce

Crystalline Ce has a remarkable phase diagram in that is the solid state analogue of a Van der Walls system with a line of discontinuous transitions ending at a critical point.

The two phases alpha and gamma have the same cubic symmetry and differ only on density just like water and vapor but in the solid state!.

However unlike water and vapor the critical exponents close to the critical point are not three dimensional Ising critical exponents, as one would naively guess from symmetries, but  classical (Gaussian) exponents.… Read the rest

Polarons in strongly correlated systems

In system with strong electron-phonon interaction, the carriers loose mobility, ultimately acquiring polaronic character. A polaron is a state in which the phonon and electron degrees of freedom are strongly entangled, and the presence of an electron is associated to a finite lattice distortion, which in turn bind

Phonon distribution function P(n) and magnetic polaron size Lp as function of the exchange coupling J, signalizing the formation of the spin/lattice polaron

s the electron leading to the so-called self-trapping effect.… Read the rest

Graphene and carbon-based new materials

The investigation of the electronic properties of graphene (single hexagonal layer of carbon atoms) has attracted a renewed interest after the development of recent techniques which permit to produce and manage single-layer (and also multilayer) samples of this materials. Nowadays truly atomic single-layer isolated samples are available as well as epitaxially grown graphene on substrates.

Fig. 1: electronic structure of graphene and Dirac-like dispersionA large interest, for its potential technological applications, concerns the investigation of optical and transport properties of both single-layer and multi-layered graphene, which are dominated by its so-called relativistic Dirac-like electronic structure (see Figure on the right).

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Competing orders in Iron based superconductors

In January 2008 a new family of superconductors has been discovered with FeAs layers. Iron is a magnetic ion and in traditional superconductors small amounts of magnetic impurities kill superconductivity so an iron based superconductor is at first sight surprising.

Tc has grow rapidly beyond 50K opening a new gate to high-Tc superconductivity. In addition the phase diagram has some similarities with the cuprates which suggest that understanding the superconductors from this new iron age can help to solve the mistery of the supercundoctors from the copper age.… Read the rest

Frustrated Phase Separation

A large variety of systems with competing short and long range interactions self-organizes in domain patterns as reviewed by Seul and Andelman. Examples range from magnetic systems (left figure A) to organic systems (left figure B).

Inhomogeneous states display a simple set of predominant morphologies like circular droplets and stripes in two-dimensional (2D) systems, and layers, cylindrical rods and spherical droplets in three-dimensional (3D) systems.… Read the rest

Polarons in organic single crystal FET’s

Organic field effect transistors (OFETs) are providing exciting prospects for potential applications in electronics. The active elements of these devices use “plastic” semiconductors, based on carbon and hydrogen. Among the advantages compared to classical silicon transistors, this new generation of components should combine mechanical flexibility, low weight, transparency and low cost. Enormous progress has been made to improve the performance of these devices through optimising the synthesis processes, drastically reducing the concentration of impurities present.… Read the rest

Unconventional antiferromagnetism due to Dzyaloshinskii-Moriya interactions

The relevance of antisymmetric superexchange interactions in spin Hamiltonians describing quantum antiferromagnetic (AF) systems has been acknowledged long ago by Dzyaloshinskii. Soon after, Moriya showed that such interactions arise naturally in perturbation theory due to the spin-orbit coupling in magnetic systems with low symmetry. Nowadays, a number of AF systems are known to belong to the class of Dzyaloshinskii-Moriya (DM) magnets, such as ?-Fe… Read the rest

Strongly Correlated Superconductivity: how can repulsion enhance Tc?

In conventional superconductors, the repulsive interaction between electrons opposes to phonon-mediated pairing. We have shown that even phonon-mediated superconductivity can be favoured by repulsion under suitable conditions which are realized in fullerenes.

Trivalent alkali-doped fullerenes are almost certainly electron-phonon superconductors, and their critical temperature can reach around 40K. There are however many experimental evidences that seem to exclude a simple BCS (or Migdal-Eliashberg) scenario, since electron-electron correlations are likely to play a central role.… Read the rest

Spin-orbit interaction and spintronics

One of the new frontiers in condensed matter physics is development and engineering of electronic devices which carrier “bit” informations in the spin degree of freedom of the electronc instead of their charge. This research line is called indeed “spintronics”. Within this context the spin-or

Rashba band-spilling and spin ordering: from J. Sinova et al., Phys. Rev. Lett. 92, 126603 (2004).

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Inhomogeneities in Cuprates

If the mechanism of high-Tc superconductivity is electronic, to understand the electronic excitation spectrum is as important as to understand phonons was important to develop BCS theory. In this regard charge and spin inhomogeneous states, often found in strongly correlated systems, are interesting because they can support new collective modes, “electronic phonons”, that would not be present in a weakly interacting fluid.… Read the rest

Unconventional electron-phonon interaction and nonadiabatic effects

The conventional understanding of the electron-phonon phenomenology in condensed matter strongly relies on the adiabatic assumption, i.e. that nuclei dynamics is much slower than the electron one. In solid crystals the validity of this assumption is usually related to the comparison of the phonon frequencies  with the Fermi energy EF. In conventional systems , assuring thus the reliability of the adiabatic assumption.… Read the rest