arXiv subjects

Danilo Puggioni

Publications and source records attributed to Danilo Puggioni.

25 records · Page 2Linked to original sources

arXiv2016

Magneto-electric coupling in type-I multiferroic ScFeO$_3$

We investigate the electronic structure and the ferroelectric properties of the recently discovered multiferroic ScFeO$_3$ by means of ab-initio calculations. The $3d$ manifold of Fe in the half-filled configuration naturally favors an antiferromagnetic ordering, with a theoretical estimate of the antiferromagnetic Néel temperature in good agreement with the experimental values. We find that the inversion symmetry-breaking is driven by the off-centering of Sc atoms, which results in a large ferroelectric polarization of $\sim$105\,$μ$C/cm$^{2}$. Surprisingly the ferroelectric polarization is sensitive to the local magnetization of the Fe atoms resulting in a large negative magnetoelectric interaction. This behavior is unexpected in type-I multiferroic materials because the magnetic and ferroelectric orders are of different origins.

cond-mat.mtrl-sci↗

arXiv2015

Electronic correlations and screening effects in the Hund's polar metal SrEuMo$_2$O$_6$

Using a first-principles approach based on density functional theory and dynamical mean field theory, we study the electronic properties of a new candidate polar metal SrEuMo$_2$O$_6$. Its electronic structure shares similarities with centrosymmetric SrMoO$_3$ and EuMoO$_3$, from which it may be considered an ordered derivative, but ferroelectric-like distortions of the divalent cations and oxygen anions lift inversion symmetry mediated by an anharmonic lattice interaction in the metallic state. We find that Hund's coupling promotes the effects of electronic correlations owing to the Mo$^{4+}$ $d^{2}$ electronic configuration, producing a correlated metallic phase far from the Mott state. The contraindication between metallicity and polar distortions is thereby alleviated through the renormalized quasiparticles, which are unable to fully screen the ordered local dipoles.

cond-mat.str-el↗

arXiv2015

Design of a Mott Multiferroic from a Non-Magnetic Polar Metal

We examine the electronic properties of newly discovered "ferroelectric" metal LiOsO$_3$ combining density-functional and dynamical mean-field theories. We show that the material is close to a Mott transition and that electronic correlations can be tuned to engineer a Mott multiferroic state in 1/1 superlattice of LiOsO$_3$ and LiNbO$_3$. We use electronic structure calculations to predict that the (LiOsO$_3$)$_1$/(LiNbO$_3$)$_1$ superlattice is a type-I multiferroic material with a ferrolectric polarization of 41.2~$μ$C cm$^{-2}$, Curie temperature of 927\,K, and Néel temperature of 671\,K. Our results support a route towards high-temperature multiferroics, \emph{i.e.}, driving non-magnetic \emph{polar metals} into correlated insulating magnetic states.

cond-mat.mtrl-sci↗

arXiv2014

Designing a robustly metallic noncenstrosymmetric ruthenate oxide with large thermopower anisotropy

The existence of approximately 30 noncentrosymmetric metals (NCSM) suggests a contraindication between crystal structures without inversion symmetry and metallic behavior. Those containing oxygen are especially scarce. Here we propose and demonstrate a design framework to remedy this property disparity and accelerate NCSM-oxide discovery: The primary ingredient relies on the removal of inversion symmetry through displacements of atoms whose electronic degrees of freedom are decoupled from the states at the Fermi level. Density functional theory calculations validate this crystal--chemistry strategy, and we predict a new polar ruthenate exhibiting robust metallicity. We demonstrate that the electronic structure is unaffected by the inclusion of spin-orbit interactions (SOI), and that cation ordered SrCaRu$_2$O$_6$ exhibits a large thermopower anisotropy ($\left|Δ\mathcal{S}_\perp\right|\sim6.3 μ\textrm{V K}^{-1}$ at 300 K) derived from its polar structure. Our findings provide chemical and structural selection guidelines to aid in the search of new NCS metals with enhanced thermopower anisotropy.

cond-mat.mtrl-sci↗

arXiv2012

Ordering and multiple phase transitions in ultra-thin nickelate superlattices

We interpret via advanced ab initio calculations the multiple phase transitions observed recently in ultra-thin LaNiO$_{3}$/LaAlO$_{3}$ superlattices. The ground state is insulating, charge-ordered, and antiferromagnetic due to concurrent structural distortion and weak valency disproportionation. We infer distinct transitions at 40 K and 150 K, respectively, from antiferromagnetic order to moment disorder, and from structurally-dimerized insulator to an undistorted metallic Pauli paramagnet (exhibiting a cuprate-like Fermi surface). The results are in satisfactory agreement with experiment.

cond-mat.mtrl-sci↗

arXiv2009

Fermi-surface pockets in magnetic underdoped cuprates from first principles

Using an innovative first-principles band theory enabling the exploration of Mott-insulating magnetic cuprates, we study the Fermi surface of underdoped Y$_{1-x}$Ca$_x$Ba$_2$Cu$_3$O$_6$ in a selection of magnetically ordered and polaronic states. All phases exhibit qualitatively similar, hole-like nodal-point small pockets. Their properties (area, masses, mass sign) only partially match those extracted from recent quantum-oscillation experiments. Ab initio calculations, therefore, do not straightforwardly support a magnetic origin of quantum oscillations.

cond-mat.supr-con↗

arXiv2009

Fermi-surface pockets in $YBa_2Cu_3O_{6.5}$ : A comparison of ab initio techniques

We study the Fermi surface of metallic, non-magnetic \textit{ortho}-II YBa$_2$Cu$_3$O$_{6.5}$ using three different density-functional-based band-structure techniques (GGA, GGA+U, PSIC). The calculated Fermi surface exhibits no pockets in GGA+U and PSIC, a minor one in GGA. Upon shifting the Fermi level in the vicinity of the calculated value, we instead observe several pocket structures. We calculate their cross-sectional areas and cyclotron masses. Overall, our calculations show no solid evidence of the existence of electron-like --nor, in fact, of any-- Fermi surface pockets in this phase. This suggests that the origin of the pockets should be sought for in other, different phases.

cond-mat.supr-con↗