arXiv subjects

M. Dutra

Publications and source records attributed to M. Dutra.

At least 19 recordsLinked to original sources

arXiv2026

Colossal Terahertz Magnetoresistance from Magnetic Polarons in EuZn$_2$P$_2$

Magnetic polarons can generate colossal magnetoresistance in magnetic semiconductors, yet their terahertz electrodynamics remain largely unexplored. Here we report magneto-terahertz spectroscopy of the Eu-based Zintl antiferromagnet EuZn$_2$P$_2$. The low-frequency conductivity shows pronounced non-Drude behavior consistent with an evolution from isolated to overlapping magnetic polarons upon cooling. The polaron relaxation time reaches a maximum near the N\'eel temperature at zero field and exhibits a strong magnetic-field dependence. This polaron-driven reshaping of the conductivity leads to a strongly frequency-dependent magnetoresistance that becomes colossal in the terahertz range, reaching about 90~\% at 1.5~THz, roughly three times larger than the zero-frequency limit value. These results demonstrate that magnetic polarons strongly govern the low-energy electrodynamics and highlight the sensitivity of terahertz spectroscopy to polaronic magnetotransport in correlated magnetic semiconductors.

cond-mat.str-el↗

arXiv2025

Engineering a Correlated Narrow-Gap Semiconductor: Effects of Ga Substitution in EuZn$_2$P$_2$

The effect of Ga substitution on the electronic, magnetic, and low-energy responses of the Zintl phase EuZn$_2$P$_2$ is investigated by electrical transport, electron spin resonance (ESR), and terahertz time-domain spectroscopy (THz-TDS). Incorporating Ga into EuZn$_2$P$_2$ (EuZn$_{1.8}$Ga$_{0.2}$P$_2$) reduces the electrical resistivity, indicating enhanced free-carrier density and a narrowed semiconducting gap. ESR confirms the persistence of Eu$^{2+}$ moments while showing a crossover from a Lorentzian to a Dysonian lineshape, consistent with reduced skin depth, increased carrier density, and the emergence of diffusive contributions. Ga-substituted compound display pronounced negative magnetoresistance linked to magnetic-polaron formation. THz-TDS reveals strong low-frequency absorption and a notable enhancement of the Drude conductivity in the substituted material, together with an increased carrier scattering time and enhanced carrier-density--to--effective-mass ratio. These results demonstrate that Ga substitution tunes charge transport, carrier dynamics, and short-range magnetic correlations in EuZn$_2$P$_2$, establishing EuZn$_{1.8}$Ga$_{0.2}$P$_2$ as a promising platform for engineering correlated narrow-gap magnetic semiconductors with enhanced electronic and spin-dependent functionalities.

cond-mat.mtrl-sci↗

arXiv2025

Pressure tuning of putative quantum criticality on YbV6Sn6

YbV$_6$Sn$_6$ is a recently discovered heavy-fermion compound that orders at T$_N\approx 0.4$ K and exhibits a magnetic field-tuned quantum critical point at $H \approx 10$ kOe. In this work, we have grown YbV$_6$Sn$_6$ single crystals by the self-flux method, to investigate their physical properties at ambient pressure and their electrical transport properties under hydrostatic pressure. At higher temperatures, we observed a decrease in the Kondo temperature, accompanied by the appearance of a local minimum followed by a local maximum, associated with the onset of the coherent Kondo regime. Power law fitting at low temperatures indicated a recovery of the Fermi-liquid regime for pressures below 1 GPa. Above 1 GPa, a reentrance of non-Fermi-liquid behavior is suggested by a decrease in the exponent $n$, accompanied by a substantial increase in the parameter $A$, indicating the approach of a new quantum criticality tuned by hydrostatic pressure. The broad range of interactions present in YbV$_6$Sn$_6$, including RKKY, crystalline electric field (CEF), and Kondo lattice effects, appears to lead to a complex phase diagram. We present a putative phase diagram featuring double quantum criticality tuned by both magnetic field and hydrostatic pressure.

cond-mat.str-el↗

arXiv2025

Spin Dynamics and Light-Induced Effects in EuZn$_2$P$_2$

The magnetic spin dynamics and optical properties of EuZn$_2$P$_2$ are studied. Single crystals grown by the Sn-flux method crystallize in the $P\overline{3}m1$ (No.~164) space group and order antiferromagnetically at $T_N=23.5$~K. $^{151}$Eu M\"ossbauer spectroscopy confirms the presence of the Eu$^{2+}$ oxidation state only and the magnetic moment angle relative to the $c$-axis is $\theta=46(3)$\textdegree. Temperature-dependent electron spin resonance (ESR) measurements reveal that spin-spin interactions predominantly govern the spin relaxation mechanisms, as evidenced by the linewidth behavior ($\Delta H$). Positive $g$-shifts ($\Delta g)$ for $H \parallel ab$ indicate the presence of local electron polarization. The ESR data support the formation of anisotropic magnetic polarons, which trap spin carriers and contribute to increased electrical resistance. Angular-dependent ESR spectra at room temperature display anisotropic behavior in both $\Delta g(\phi)$ and $\Delta H(\phi)$, with a dominant three-dimensional component $C_{3D}$, indicative of robust interlayer coupling and antiferromagnetic fluctuations. Under light illumination, a small broadening of $\Delta H$ is observed. Furthermore, a photovoltaic effect is identified in EuZn$_2$P$_2$, with photodetector performance metrics suggesting promising capabilities for future optoelectronic devices.

cond-mat.str-el↗

arXiv2025

Holographic hybrid stars with slow phase transitions

The $D_3$-$D_7$ holographic model is used to describe the core of the hybrid star, composed by quark matter, while its crust is modeled from a hadronic relativistic mean field (RMF) model capable of reproducing low-energy nuclear physics data as well as some astrophysical observations. The $D_3$-$D_7$ brane configuration and the RMF model lead to an equation of state that is used to solve the Tolman-Oppenheimer-Volkoff equations. For different model parameters, the mass-radius diagram is presented. The conditions for the dynamic stability of stellar configurations are discussed, considering the radial oscillation criterion for hybrid stars with slow phase transitions. Strikingly, it is shown that the models generate stable star configurations with a core of quarks. We compare our results with NICER observational data for the pulsars PSR J0030+0451 and PSR J0740+6620 and show that the compact stars generated from this method fall within the corresponding observational regions.

nucl-th↗

arXiv2024

Supernova Remnants with Mirror Dark Matter and Hyperons

For the first time, we use relativistic mean-field (RMF) approximation with density-dependent couplings, adjusted by the DDME2 parameterization, to investigate the effects of dark matter on supernova remnants. We calculate the nuclear equation of state for nuclear and dark matter separately, under the thermodynamic conditions related to the evolution of supernova remnants. A mirrored model is adopted for dark matter, and its effect on remnant matter is studied using a two-fluid scenario. At each stage of the remnant evolution, we assume that dark and ordinary matter have the same entropy and lepton fraction, and a fixed proportion of dark matter mass fraction is added to the stellar matter to observe its effects on some microscopic and macroscopic properties of the star. We observe that dark matter in the remnant core reduces the remnant's maximum mass, radius, and tidal deformability. Moreover, dark matter heats the remnant matter and alters particle distributions, thereby decreasing its isospin asymmetry and increasing the sound speed through the matter.

hep-ph↗

arXiv2024

Gravitational wave asteroseismology of dark matter hadronic stars

The influence of the dark matter mass~($M_{\chi}$) and the Fermi momentum~($k_{F}^{\dm}$) on the $f_0$-mode oscillation frequency, damping time parameter, and tidal deformability of hadronic stars are studied by employing a numerical integration of hydrostatic equilibrium, nonradial oscillation, and tidal deformability equations. The matter inside the hadronic stars follows the NL3* equation of state. We obtain that the influence of $M_{\chi}$ and $k_F^{\dm}$ is observed in the $f_0$-mode, damping tome parameter, and tidal deformability. Finally, the correlation between the tidal deformability of the GW$170817$ event with $M_{\chi}$ and $k_F^{\dm}$ are also investigated.

hep-ph↗

arXiv2023

Bayesian analysis of a relativistic hadronic model constrained by recent astrophysical observations

We use Bayesian analysis in order to constrain the equation of state for nuclear matter from astrophysical data related to the recent measurements from the NICER mission, LIGO/Virgo collaboration, and probability distributions of mass and radius from other 12 sources, including thermonuclear busters, and quiescent low-mass X-ray binaries. For this purpose, we base our study on a relativistic hadronic mean field model including an $\omega-\rho$ interaction. Our results indicate optimal ranges for some bulk parameters at the saturation density, namely, effective mass, incompressibility, and symmetry energy slope ($L_0$). For instance, we find $L_0 = 50.79^{+15.16}_{-9.24}$ MeV (Case 1) and $L_0 = 75.06^{+8.43}_{-4.43}$ MeV (Case 2) in a $68\%$ confidence interval for the 2 cases analyzed (different input ranges for $L_0$ related to the PREX-II data). The respective parametrizations are in agreement with important nuclear matter constraints, as well as observational neutron star data, such as the dimensionless tidal deformability of the GW170817 event. From the mass-radius curves obtained from these best parametrizations, we also find the ranges of $11.97 \mbox{ km}\leqslant R_{1.4}\leqslant 12.73 \mbox{ km}$ (Case 1) and $12.34 \mbox{ km}\leqslant R_{1.4}\leqslant 13.06 \mbox{ km}$ (Case 2) for the radius of the $1.4M_\odot$ neutron star.

nucl-th↗

arXiv2023

Recent astrophysical observations reproduced by a short-range correlated van der Waals-type model?

We perform an improvement in a van der Waals-type model by including it effects of short-range correlations (SRC). Attractive and repulsive parts of the nucleon-nucleon interaction are assumed to be density-dependent functions, more specifically, we adopt the Carnahan-Starling (CS) method for the latter, and a suitable expression for the former in order to reproduce the structure of the Clausius (C) real gas model. The parametrizations of the resulting model, named as CCS-SRC model, are shown to be capable of reproducing the flow constraint at the high-density regime of symmetric nuclear matter for incompressibility values inside the range of $K_0=(240\pm 20)$ MeV. In the context of stellar matter, our findings point out a good agreement of the CCS-SRC model with recent astrophysical observational data, namely, mass-radius contours and dimensionless tidal deformability regions and values, coming from gravitational waves data related to the GW170817 and GW190425 events, and from the NASA's Neutron star Interior Composition Explorer (NICER) mission. Furthermore, the values for the symmetry energy slope of the model ($L_0$) are in agreement with a recent range found for this quantity, claimed to be consistent with results reported by the updated lead radius experiment (PREX-2) collaboration. In this case, higher values of $L_0$ are favored, while the opposite scenario does not allow simultaneous compatibility between the model and the astrophysical data.

nucl-th↗

arXiv2023

Dark matter effects in modified teleparallel gravity

This work investigates dark matter (DM) effects in compact objects in modified teleparallel gravity (MTG) in which a modification of Teleparallel Equivalent to General Relativity is used. We applied a tetrad to the modified field equations where a set of relations is found. The conservation equation allows us to rewrite our Tolman-Oppenheimer-Volkoff equations with an effective gravitational coupling constant. As input to these new equations, we use a relativistic mean-field (RMF) model with dark matter content included, obtained from a Lagrangian density with both, hadronic and dark particle degrees of freedom, as well as the Higgs boson, used as a mediator in both sectors of the theory. Through numerical calculations, we analyze the mass-radius diagrams obtained from different parametrizations of the RMF-DM model, generated by assuming different values of the dark particle Fermi momentum and running the free parameter coming from the MTG. Our results show that it is possible for the system simultaneously support more DM content, and be compatible with recent astrophysical data provided by LIGO and Virgo Collaboration, as well as by NASA's Neutron star Interior Composition Explorer (NICER).

gr-qc↗

arXiv2023

Neutron Stars in Modified Teleparallel Gravity

We investigate compact objects in modified teleparallel gravity with realistic equations of state. We propose a modification of Teleparallel Equivalent to General Relativity, then an appropriate tetrad is applied to the field equations. A specific set of relations showing an equivalency between our gravitational model and the New General Relativity is found. The conservation equation implies that our Tolman-Oppenheimer-Volkoff equations are presented with an effective gravitational coupling constant. Numerical analysis using realistic equations of state is made, and the behavior of mass, radius, and the relation mass-radius as functions of a free parameter of our model is also investigated.

gr-qc↗

arXiv2022

Dark particle mass effects on neutron star properties from a short-range correlated hadronic model

In this work we study a relativistic mean-field (RMF) hadronic model, with nucleonic short-range correlations (SRC) included, coupled to dark matter (DM) through the Higgs boson. We study different parametrizations of this model by running the dark particle Fermi momentum, and its mass in the range of $50$ GeV $\leqslant M_\chi\leqslant 500$ GeV, compatible with experimental spin-independent scattering cross-sections. By using this RMF-SRC-DM model, we calculate some neutron star quantities, namely, mass-radius profiles, dimensionless tidal deformabilities, and crustal properties. Our findings show that is possible to construct RMF-SRC-DM parametrizations in agreement with constraints provided by LIGO and Virgo collaboration (LVC) on the GW170817 event, and recent observational data from the NICER mission. Furthermore, we show that the increase of $M_\chi$ favors the model to attain data from LVC regarding the tidal deformabilities. Higher values of $M_\chi$ also induce a reduction of the neutron star crust (mass and thickness), and cause a decrease of the crustal fraction of the moment of inertia ($I_{\rm{\tiny crust}}/I$). Nevertheless, we show that some RMF-SRC-DM parametrizations still exhibit $I_{\rm{\tiny crust}}/I>7\%$, a condition that explains the glitch activity in rotation-powered pulsars such as the Vela one. Therefore, dark matter content can also be used for describing such a phenomenon.

nucl-th↗

arXiv2022

Dark matter effects on tidal deformabilities and moment of inertia in a hadronic model with short-range correlations

In this work we study the outcomes related to dimensionless tidal deformability $(\Lambda)$ obtained through a relativistic mean-field (RMF) hadronic model including short-range correlations (SRC) and dark matter (DM) content [Phys. Rev. D 105, 023008 (2022)]. As a dark particle candidate, we use the lightest neutralino interacting with nucleons through the Higgs boson exchange. In particular, we test the model against the constraints regarding the observation of gravitational waves from the binary neutron star merger GW170817 event provided by LIGO and Virgo collaboration (LVC). We show that $\Lambda$ decreases as the dark particle Fermi momentum ($k_F^{DM}$) increases. This feature favors the RMF-SRC-DM model used here to satisfy the limits of $\Lambda_{1.4}=190^{+390}_{-120}$ ($\Lambda$ of a $1.4M_\odot$ neutron star), and $\tilde{\Lambda}=300^{+420}_{-230}$ given by the LVC. We also show that as $k_F^{DM}$ increases, $\Lambda_1$ and $\Lambda_2$, namely, tidal deformabilities of the binary system, are also moved to the direction of the GW170817 observational data. Finally, we verify that the inclusion of DM in the system does not destroy the \mbox{$I$-Love} relation (correlation between $\Lambda$ and dimensionless moment of inertia, $\bar{I}$). The observation data for $\bar{I}_\star\equiv\bar{I}(M_\star)=11.10^{+3.68}_{-2.28}$, with $M_\star=1.338M_\odot$, is attained by the RMF-SRC-DM model.

nucl-th↗

arXiv2021

Dark matter component in hadronic models with short-range correlations

A relativistic mean field hadronic model with a dark matter (DM) particle coupled to nucleons including short-range correlations (SRC) is applied to study neutron stars (NS). The lightest neutralino is chosen as the dark particle candidate, which interacts with nucleons by the exchange of Higgs bosons. A detailed thermodynamical analysis shows that the contribution of the DM fermions to the energy density of the matter composed by these particles and nucleons is completely dominated by the DM kinetic terms. The model reproduces satisfactorily the constraints on the mass-radius diagram obtained from the analysis of the combined data from the NICER mission, LIGO and Virgo collaborations, and mass measurements from radio observations. We show that the SRC balance the reduction of the neutron star mass due to the DM component, and because of that the model is able to present more massive NS. We also present a study of the effect, in the NS mass-radius profiles, of the uncertainties in some bulk parameters related to the hadronic sector. We find that it is possible to generate parametrizations, with DM content, compatible with the recent astrophysical constraints and with the uncertainty in the symmetry energy slope obtained from the results reported by the updated Lead Radius EXperiment (PREX-2).

nucl-th↗

arXiv2021

PNJL model at zero temperature: three-flavor case

We propose a three-flavor version of the Polyakov-Nambu-Jona-Lasino (PNJL) model at zero temperature regime, by implementing a traced Polyakov loop ($\Phi$) dependence in the scalar, vector and 't Hooft channel strengths. We study the thermodynamics of this model, named as PNJL0, with special attention for the first order confinement/deconfinement phase transition for which $\Phi$ is the order parameter. For the symmetric quark matter case, an interesting feature observed is a strong reduction of the constituent strange quark mass ($M_s$) at the chemical potential related to point where deconfinement takes place. The emergence of $\Phi$ favors the restoration of chiral symmetry even for the strange quark. We also investigate the charge neutral system of quarks and leptons in weak equilibrium. As an application, we construct a hadron-quark phase transition with a density dependent hadronic model coupled to the SU(3) PNJL0 model. In this case, the quark side is composed by deconfined particles. This approach is used to determine mass-radius profiles compatible with recent data from the Neutron Star Interior Composition Explorer (NICER) mission.

hep-ph↗

arXiv2021

Neutron star crustal properties from relativistic mean-field models and bulk parameters effects

We calculate crustal properties of neutron stars, namely, mass ($M_{\rm crust}$), radius ($R_{\rm crust}$) and fraction of moment of inertia ($\Delta I/I$) from parametrizations of hadronic relativistic mean-field (RMF) model consistent with symmetric and asymmetric nuclear matter constraints, as well as some stellar boundaries. We verify which one are also in agreement with restrictions of $\Delta I/I \geqslant 1.4\%$ and $\Delta I/I \geqslant 7\%$ related to the glitching mechanism observed in pulsars, such as the Vela one. The latter constraint explains the glitches phenomenon when entrainment effects are taken into account. Our findings indicate that these parametrizations pass in the glitching limit for a neutron star mass range of $M\leqslant 1.82M_\odot$ ($\Delta I/I \geqslant 1.4\%$), and $M\leqslant 1.16M_\odot$ ($\Delta I/I \geqslant 7\%$). We also investigate the influence of nuclear matter bulk parameters on crustal properties and find that symmetry energy is the quantity that produces the higher variations on $M_{\rm crust}$, $R_{\rm crust}$, and~$\Delta I/I$. Based on the results, we construct a particular RMF parametrization able to satisfy $\Delta I/I \geqslant 7\%$ even at $M=1.4M_\odot$, the mass value used to fit data from the softer component of the Vela pulsar X-ray spectrum. The model also presents compatibility with observational data from PSR J1614-2230, PSR J0348+0432, and MSP J0740+6620 pulsars, as well as, with data from the Neutron Star Interior Composition Explorer (NICER) mission.

nucl-th↗

arXiv2020

Neutron stars in $f(\mathcal{R,T})$ gravity using realistic equations of state in the light of massive pulsars and GW170817

In this work we investigate neutron stars (NS) in $f(\mathcal{R,T})$ gravity for the case $R+2\lambda\mathcal{T}$, $\mathcal{R}$ is the Ricci scalar and $\mathcal{T}$ the trace of the energy-momentum tensor. The hydrostatic equilibrium equations are solved considering realistic equations of state (EsoS). The NS masses and radii obtained are subject to a joint constrain from massive pulsars and the event GW170817. The parameter $\lambda$ needs to be negative as in previous NS studies, however we found a minimum value for it. The value should be $|\lambda|\lesssim0.02$ and the reason for so small value in comparison with previous ones obtained with simpler EsoS is due to the existence of the NS crust. The pressure in theory of gravity depends on the inverse of the sound velocity $v_s$. Since, $v_s$ is low in the crust, $|\lambda|$ need to be very small. We found that the increment in the star mass is less than $1\%$, much smaller than previous ones obtained not considering the realistic stellar structure, and the star radius cannot become larger, its changes compared to GR is less than $3.6\%$ in all cases. The finding that using several relativistic and non-relativistic models the variation on the NS mass and radius are almost the same for all the EsoS, manifests that our results are insensitive to the high density part of the EsoS. It confirms that stellar mass and radii changes depend only on crust, where the EoS is essentially the same for all the models. The NS crust effect implying very small values of $|\lambda|$ does not depend on the theory's function chosen, since for any other one the hydrostatic equilibrium equation would always have the dependence $1/v_s$. Finally, we highlight that our results indicate that conclusions obtained from NS studies done in modified theories of gravity without using realistic EsoS that describe correctly the NS interior can be unreliable.

astro-ph.HE↗

arXiv2020

GW170817 constraints analyzed with Gogny forces and momentum-dependent interactions

A set of equations of state obtained from finite-range Gogny forces and momentum-dependent interactions is used to investigate the recent observation of gravitational waves from the binary neutron star merger GW170817 event. For this set of interactions, we have calculated the neutron star tidal deformabilities (related to the second Love number), the mass-radius diagram, and the moment of inertia~($I$). The $I$-Love relation has been verified. We also have found strong correlations among the tidal deformability of the canonical neutron star, its radius, and the derivatives of the nuclear symmetry energy at the saturation density. Most of the obtained results are located within the constraints of the tidal deformabilities extracted from the GW170817 detection.

nucl-th↗