arXiv subjects

Federico Caglieris

Publications and source records attributed to Federico Caglieris.

23 records · Page 2Linked to original sources

arXiv2020

Evolution of the nematic susceptibility in LaFe$_{1-x}$Co$_x$AsO

The identification of electronic nematicity across series of iron-based superconductors raises the question of its relationship with superconductivity and other ordered states. Here, we report a systematic elastoresistivity study on LaFe$_{1-x}$Co$_x$AsO single crystals, which have well separated structural and magnetic transition lines. All crystals show Curie-Weiss-like nematic susceptibility in the tetragonal phase. The extracted nematic temperature is monotonically suppressed upon cobalt doping, and changes sign around the optimal doping level, indicating a possible nematic quantum critical point beneath the superconducting dome. The amplitude of nematic susceptibility shows a peculiar double-peak feature. This could be explained by a combined effect of different contributions to the nematic susceptibility, which are amplified at separated doping levels of LaFe$_{1-x}$Co$_x$AsO.

cond-mat.supr-con↗

arXiv2020

A hydrodynamical description for magneto-transport in the strange metal phase of Bi-2201

High temperature superconductors are strongly coupled systems which present a complicated phase diagram with many coexisting phases. This makes it difficult to understand the mechanism which generates their singular transport properties. Hydrodynamics, which mostly relies on the symmetries of the system without referring to any specific microscopic mechanism, constitutes a promising framework to analyze these materials. In this paper we show that in the strange metal phase of the cuprates, a whole set of transport coefficients are described by a universal hydrodynamic framework once one accounts for the effects of quantum critical charge density waves. We corroborate our theoretical prediction by measuring the DC transport properties of Bi-2201 close to optimal doping, proving the validity of our approach. Our argument can be used as a consistency check to understand the universality class governing the behavior of high temperature cuprate superconductors.

cond-mat.str-el↗

arXiv2019

Topological electronic structure and intrinsic magnetization in MnBi$_4$Te$_7$: a Bi$_2$Te$_3$-derivative with a periodic Mn sublattice

Combinations of non-trivial band topology and long-range magnetic order hold promise for realizations of novel spintronic phenomena, such as the quantum anomalous Hall effect and the topological magnetoelectric effect. Following theoretical advances material candidates are emerging. Yet, a compound with a band-inverted electronic structure and an intrinsic net magnetization remains unrealized. MnBi$_2$Te$_4$ is a candidate for the first antiferromagnetic topological insulator and the progenitor of a modular (Bi$_2$Te$_3$)$_n$(MnBi$_2$Te$_4$) series. For $n$ = 1, we confirm a non-stoichiometric composition proximate to MnBi$_4$Te$_7$ and establish an antiferromagnetic state below 13 K followed by a state with net magnetization and ferromagnetic-like hysteresis below 5 K. Angle-resolved photoemission experiments and density-functional calculations reveal a topological surface state on the MnBi$_4$Te$_7$(0001) surface, analogous to the non-magnetic parent compound Bi$_2$Te$_3$. Our results render MnBi$_4$Te$_7$ as a band-inverted material with an intrinsic net magnetization and a complex magnetic phase diagram providing a versatile platform for the realization of different topological phases.

cond-mat.mtrl-sci↗

arXiv2019

Berry curvature unravelled by the Nernst effect in Mn$_3$Ge

The discovery of topological quantum materials represents a striking innovation in modern condensed matter physics with remarkable fundamental and technological implications. Their classification has been recently extended to topological Weyl semimetals, i.e., solid state systems which exhibit the elusive Weyl fermions as low-energy excitations. Here we show that the Nernst effect can be exploited as a sensitive probe for determining key parameters of the Weyl physics, applying it to the non-collinear antiferromagnet Mn$_3$Ge. This compound exhibits anomalous thermoelectric transport due to enhanced Berry curvature from Weyl points located extremely close to the Fermi level. We establish from our data a direct measure of the Berry curvature at the Fermi level and, using a minimal model of a Weyl semimetal, extract for the first time the Weyl point energy and their distance in momentum-space.

cond-mat.str-el↗

arXiv2018

Evidence of the isoelectronic character of F doping in SmFeAsO(1-x)F(x): a first-principles investigation

We study the electronic structure of the SmFeAsO(1-x)F(x) alloy by means of first-principle calculations. We find that, contrary to common believe, F-doping does not change the charge balance between electrons and holes free-carriers in SmFeAsO(1-x)F(x). For energies within a narrow energy range across E_F, the effect of F-doping on the band structure dispersion is tiny in both the paramagnetic and stripe antiferromagnetic phase. The charge balance between the conducting FeAs-layer and the SmO(1-x)F(x) charge reservoir layer is not influenced by the compositional change. The additional charge carried by fluorine, with respect to the oxygen, is compensated by a change in the oxidation state of the Sm ion from 3+ to 2+. A comparison with the SmFe(1-x)Co(x)AsO system shows that such charge compensation by the Sm ion is not shared by donors substituting at the Fe site.

cond-mat.supr-con↗