arXiv subjects

Gicela Saucedo Salas

Publications and source records attributed to Gicela Saucedo Salas.

7 recordsLinked to original sources

arXiv2026

Origin of High-Temperature Antiferromagnetic Order in a van der Waals Material

While Van der Waals (vdW) itinerant antiferromagnets with high Neel temperatures (TN) are highly desirable for spintronics, they remain relatively scarce. Here, we unravel the physical origin of the unusually high TN (= 250 K) in the newly identified vdW compound (Fe0.65Co0.35)4GeTe2. The substitution of Co in Fe4GeTe2 induces layer-selective Fe-Co ordering and stabilizes a robust antiferromagnetic (AFM) state primarily driven by Co moments. The AFM order is further strengthened by enhanced electronic correlations of quasi-localized Co 3d-states at the Fermi level, giving rise to an itinerant-localized duality of the 3d electrons. This interplay generates strong magnetic correlations well above TN and stabilizes low-temperature spin canting with a possible nontrivial Berry curvature. Our results establish (Fe0.65Co0.35)4GeTe2 as a rare material bridging fundamental magnetic interactions with potential applications in AFM spintronics.

cond-mat.mtrl-sci↗

arXiv2026

Field-direction sensitivity of Kondo hybridization in UTe$_2$

Neutron scattering experiments on the spin-triplet superconductor UTe$_2$ have established that the dominant low-energy magnetic response is along Brillouin zone boundaries, resembling the magnetic susceptibility of narrow-gap interband excitations. We report a study of the sensitivity of these excitations to magnetic field along the crystallographic $\hat{a}$-axis. Up to fields of $μ_0 H$=13 T, the maximal inelastic neutron spectral weight increases in energy transfer, with a pronounced increase in $d\hbarω_{peak}/dH$ near $μ_0 H$=7 T. This behavior parallels the field and temperature dependent features of the electrical resistivity that are associated with Kondo hybridization. Our measurements suggest that $\hat{a}$-axis fields near $μ_0 H$=7~T induce a change in the hybridization between heavy $f$-electrons and the bare conduction band.

cond-mat.str-el↗

arXiv2026

Limited coincidence between ultrahigh-field superconductivity and line of metamagnetic endpoints in UTe$_2$

The field-dependent magnetization of UTe$_2$ was measured through the metamagnetic transition at a variety of field angles, tracking how the step in magnetization evolves with fields tilted away from the $b$ axis. For fields oriented within the $ab$ plane, jumps in both $M_a$ and $M_b$ vanish approximately 18° away from the $b$ axis. From contactless conductivity measurements, we find that the halo-like high-field superconducting region extends to the $ab$ plane, where it exists only within a very narrow ($<$1°) angular range near the termination of the metamagnetic phase boundary and extends beyond the highest measured field of 73 T. As the field orientation tilts towards the $c$ axis, the superconducting and metamagnetic phase boundaries no longer coincide and exhibit distinct trends.

cond-mat.supr-con↗

arXiv2025

High-Field Superconducting Halo in UTe$_2$

Heavy fermion UTe$_2$ is a promising candidate for topological superconductivity that also exhibits multiple high-field superconducting phases. The SC$_{\rm{FP}}$ phase has only been observed in off-axis magnetic fields in the $bc$ plane at fields greater than 40 teslas, a striking scale given its critical temperature of only 2 kelvins. Here, we extend measurements of this unique superconducting state outside of the $bc$ plane and reveal its core structure. The SC$_{\rm{FP}}$ phase is not confined to fields in the $bc$ plane and in fact wraps around the $b$ axis in a halo-like fashion. In other words, this superconducting state, which exists in fields above 73 teslas, is stabilized by a field component perpendicular to the magnetic easy axis. These remarkable field scales further underscore UTe$_2$'s unique magnetophilic superconducting tendencies and suggest an underlying pairing mechanism that is qualitatively distinct from known theories for field-enhanced superconductivity. Phenomenological modeling points to a two-component, non-unitary spin triplet order parameter with finite orbital momentum of the Cooper pairs as a natural explanation for the field-angle dependence of the upper critical field of the SC$_{\rm{FP}}$ phase.

cond-mat.supr-con↗

arXiv2024

Connection between f-electron correlations and magnetic excitations in UTe2

The detailed anisotropy of the low-temperature, low-energy magnetic excitations of the candidate spin-triplet superconductor UTe$_2$ is revealed using inelastic neutron scattering. The magnetic excitations emerge from the Brillouin zone boundary at the high symmetry $Y$ and $T$ points and disperse along the crystallographic $\hat{b}$-axis. In applied magnetic fields to at least $μ_0 H=11$~T along the $\hat{c}-$axis, the magnetism is found to be field-independent in the $(hk0)$ plane. The scattering intensity is consistent with that expected from U$^{3+}$/U$^{4+}$ $f$-electron spins with preferential orientation along the crystallographic $\hat{a}$-axis, and a fluctuating magnetic moment of 2.3(7) $μ_B$. These characteristics indicate that the excitations are due to intraband spin excitons arising from $f$-electron hybridization.

cond-mat.str-el↗

arXiv2024

Itinerant A-type Antiferromagnetic Order in Co$_{0.25}$TaSe$_2$

We present the magnetic behavior and resulting transport properties of TaSe$_2$ when intercalated by magnetically active cobalt cations. Acting as the layered host, TaSe$_2$ is a transition metal dichalcogenide (TMD) that adopts the 2H-polytype. We find through our single crystal and powder diffraction studies that we can prepare the stoichiometry Co$_{0.25}$TaSe$_2$, which crystallizes in the centrosymmetric space group $P6_3/mmc$. From magnetic susceptibility and x-ray photoelectron spectroscopy measurements, we find a transition consistent with antiferromagnetic order below the temperature $T_N$ = 173 K and Co$^{2+}$ in the high-spin state. Neutron powder diffraction and specific heat measurements, however, point to a much smaller than anticipated ordered moment in this sample. From the neutron results, the magnetic structure can be described as an A-type antiferromagnet with an ordered moment size of 1.35(11) $μ_B$ per Co cation. The direction of the moments are all long the c-axis, which is consistent with the magnetization and susceptibility studies showing this direction to be the easy axis. Interestingly, we find that a weak and subtle ferromagnetic component appears to exist along the $ab$-plane of the Co$_{0.25}$TaSe$_2$ crystals. We place the results of this work in the context of other magnetic-ion intercalated TMDs, especially those of Ta and Nb.

cond-mat.str-el↗

arXiv2023

Orphan High Field Superconductivity in Non-Superconducting Uranium Ditelluride

Reentrant superconductivity is a phenomenon in which the destructive effects of magnetic field on superconductivity are mitigated, allowing a zero-resistance state to survive under conditions that would otherwise destroy it. Typically, the reentrant superconducting region derives from a zero-field parent superconductor. Here, we show that in specifically-prepared UTe$_2$ crystals, extremely large magnetic field gives rise to an unprecedented high field superconductor that lacks a zero-field parent phase. This orphan superconductivity exists at fields between 37 T and 52 T, over a smaller angular range than observed in superconducting UTe$_2$. The stability of field-induced orphan superconductivity is a challenge to existing theoretical explanations, and underscores the likelihood of a field-induced modification of the electronic structure of UTe$_2$.

cond-mat.supr-con↗