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5 results on '"Jonathan Frassineti"'

1. Electron-hole asymmetry in the phase diagram of carrier-tuned CsV3Sb5

Author

Andrea N. Capa Salinas, Brenden R. Ortiz, Calvin Bales, Jonathan Frassineti, Vesna F. Mitrović, and Stephen D. Wilson

Subjects
charge density waves, superconductivity, kagome lattice, carrier doping, topological metal, Electrical engineering. Electronics. Nuclear engineering, TK1-9971
Abstract

In this work, we study the effect of electron doping on the kagome superconductor CsV3Sb5. Single crystals and powders of CsV3Sb5−xTex are synthesized and characterized via magnetic susceptibility, nuclear quadrupole resonance, and x-ray diffraction measurements, where we observe a slight suppression of the charge density wave transition temperature and superconducting temperature with the introduction of electron dopants. In contrast to hole doping, both transitions survive relatively unperturbed up to the solubility limit of Te within the lattice. A comparison is presented between the electronic phase diagrams of electron- and hole-tuned CsV3Sb5.

Published
2023
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2. Microscopic nature of the charge-density wave in the kagome superconductor RbV_{3}Sb_{5}

Author

Jonathan Frassineti, Pietro Bonfà, Giuseppe Allodi, Erick Garcia, Rong Cong, Brenden R. Ortiz, Stephen D. Wilson, Roberto De Renzi, Vesna F. Mitrović, and Samuele Sanna

Subjects
Physics, QC1-999
Abstract

The recently discovered vanadium-based Kagome metals AV_{3}Sb_{5} (A = K, Rb, Cs) undergo a unique phase transition into charge-density wave (CDW) order which precedes both unconventional superconductivity and time-reversal symmetry breaking. Therefore the essential first step in building a full understanding of the role of CDW in establishing these unconventional phases is to unveil the symmetries and the microscopic nature of the charge-ordered phase. Here, we determine the exact structure of the 2×2×2 superlattice that develops below the charge-density wave ordering temperature (T_{CDW}) in RbV_{3}Sb_{5}. We present a comprehensive set of ^{51}V, ^{87}Rb, and ^{121}Sb nuclear magnetic resonance (NMR) measurements and density functional theory simulations of NMR observables to provide a unique site-selective view into the local nature of the charge-ordered phase. The combination of these experimental results with simulations provides compelling evidence that the CDW structure prevailing below 103 K in RbV_{3}Sb_{5} is the so-called inverse Star of David pattern, π-shifted along the c axis. These findings put severe constraints on the topology of these Kagome compounds and thus provide essential guidance for the development of an appropriate theoretical framework for predicting properties of exotic electronic orders arising within the CDW phase.

Published
2023
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5. UNDI: An open-source library to simulate muon-nuclear interactions in solids

Author

Ifeanyi John Onuorah, Jonathan Frassineti, Muhammad Maikudi Isah, Pietro Bonfà, Samuele Sanna, Bonfa P., Frassineti J., Isah M.M., Onuorah I.J., and Sanna S.

Subjects
Physics, Muon, Magnetic moment, Spin polarization, Magnetism, Spin Hamiltonian, General Physics and Astronomy, Data analysi, Muon spin spectroscopy, 01 natural sciences, 010305 fluids & plasmas, Computational physics, Hardware and Architecture, Electric field, 0103 physical sciences, Python 3, Muon spin rotation and relaxation spectroscopy, 010306 general physics, Magnetic dipole, Density Functional Theory, Electric field gradient
Abstract

We present UNDI, an open-source program to analyze the time dependent spin polarization of an isolated muon interacting with the surrounding nuclear magnetic dipoles in the context of standard muon spin rotation and relaxation spectroscopy experiments. The code can perform both exact and approximated estimates of the muon polarization function in presence of external fields and electric field gradients on the nuclei surrounding the muon. We show that this tool, combined to ab initio estimations of the electric field gradient at the nuclei interacting with the muon, can become a valuable complement to supercell based identifications of muon sites in crystals when large nuclear magnetic moments are present in the sample. In addition, it allows to properly investigate physical properties influenced by the presence of a non-negligible electric field gradient such as avoided level crossing resonance, nature of the ground state, disentanglement of electronic and nuclear magnetic moments or charge ordered states. The efficiency and effectiveness of this method is shown along the lines of three realistic examples. Program summary Program Title: UNDI CPC Library link to program files: http://dx.doi.org/10.17632/grp8njy6gz.1 Developer’s repository link: https://github.com/bonfus/undi Code Ocean capsule: https://codeocean.com/capsule/8365303 Licensing provisions: GPLv3 Programming language: Python Nature of problem: To simplify and potentially automate the analysis of the nuclear contribution to muon polarization functions in crystalline materials. Solution method: A python library that provides a set of tools to efficiently solve the spin Hamiltonian describing the interaction between the muon and its neighboring nuclei. The code provides the time development of the spin polarization of the muon subject to external fields and accounts for quadrupolar interactions at the nuclear sites. The solution is sought at quantum level accuracy and Hilbert spaces with dimension up to one million can be handled, thus providing accurate results for all standard experimental conditions.

Published
2021

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