Abstract
In this letter, we have examined the superconducting ground state of the HfV$_2$Ga$_4$ compound using resistivity, magnetization, zero-field (ZF) and transverse-field (TF) muon-spin relaxation and rotation ($\mu$SR) measurements. Resistivity and magnetization unveil the onset of bulk superconductivity with $T_{\bf c}\sim$ 3.9~K, while TF-$\mu$SR measurements show that the temperature dependence of the superfluid density is well described by a nodal two-gap $s$+$d$-wave order parameter model. In addition, ZF muon relaxation rate increases with decreasing temperature below 4.6 K, indicating the presence of weak spin fluctuations. These observations suggest an unconventional multiband nature of the superconductivity possibly arising from the distinct $d$-bands of V and Hf ions with spin fluctuations playing an important role. To better understand these findings, we carry out first-principles electronic-structure calculations, further highlighting that the Fermi surface consists of multiple disconnected sheets with very different orbital weights and spin-orbit coupling, bridging the way for a nodal multiband superconductivity scenario. In this vein, therefore, HfV$_2$Ga$_4$-family stands out as an open avenue to novel unexplored unconventional superconducting compounds, such as ScV$_2$Ga$_4$ and ZrV$_2$Ga$_4$, and other many rare earths based materials.
Highlights
Rapid CommunicationsV-based superconductors [8,9] are usually mediated by an electron-phonon coupling mechanism, showing a conventional BCS behavior without expressive spin-fluctuation manifestations
3Materials Engineering Department (Demar), Escola de Engenharia de Lorena, Universidade de São Paulo (EEL-USP), Lorena-SP, Brazil 4ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX, United Kingdom. In this Rapid Communication, we have examined the superconducting ground state of the HfV2Ga4 compound using resistivity, magnetization, zero-field (ZF), and transverse-field (TF) muon-spin relaxation and rotation measurements
The ZF muon relaxation rate increases with decreasing temperature below 4.6 K, suggesting the presence of weak spin fluctuations. These observations pointed to an unconventional multiband nature of the superconducting ground state. To better understand these findings, we carry out first-principles electronic-structure calculations, further highlighting multiple disconnected sheets with very different orbital weights and spin-orbit coupling composing the Fermi surface, bridging the way for a nodal multiband superconductivity scenario
Summary
V-based superconductors [8,9] are usually mediated by an electron-phonon coupling mechanism, showing a conventional BCS behavior without expressive spin-fluctuation manifestations In this Rapid Communication, we present unambiguous evidence of two-gap superconductivity in HfV2Ga4 using transverse-field (TF) muon-spin rotation (μSR) measurement. In opposition to what was expected for V-based superconductors and from previous experimental and theoretical attempts, we have discovered an unconventional, and uncommon, superconducting order parameter with (s + d )-wave pairing symmetry and experimental indications of spin fluctuations These experimental findings are further supported by density functional theory (DFT) calculations. Several compounds within the HfV2Ga4 family, such as ScV2Ga4, ZrV2Ga4 [6,7], and many rareearth-based materials, stand out as an open avenue and an
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