Field-induced compensation of magnetic exchange as the origin of superconductivity above \texorpdfstring{40\,T}{40~T} in \texorpdfstring{\UTe}{UTe2}

The potential spin-triplet heavy-fermion superconductor \UTe exhibits signatures of multiple distinct superconducting phases. For field aligned along the $b$ axis, a metamagnetic transition occurs at $\mu_0$\Hm$\approx35\,$T. It is associated with magnetic fluctuations that may be beneficial for the field-enhanced superconductivity surviving up to \Hm. Once the field is tilted away from the $b$ towards the $c$ axis, a reentrant superconducting phase emerges just above \Hm. In order to better understand this remarkably field-resistant superconducting phase, we conducted magnetic-torque and magnetotransport measurements in pulsed magnetic fields. We determine the record-breaking upper critical field of $\mu_0$\Hc$\approx 73\,$T and its evolution with angle. Furthermore, the normal-state Hall effect experiences a drastic suppression indicative of a reduced band polarization above \Hm in the angular range around $30^\circ$ caused by a partial compensation between the applied field and an exchange field. This promotes the Jaccarino-Peter effect as a possible mechanism for the reentrant superconductivity above \Hm.Comment: Main text: 27 pages, 4 figure, supplement: 10 pages, 5 figure

Platinum Diolefin Complexes - Synthesis, Structures, and Cytotoxicity

The synthesis, spectroscopy, structures and chemical reactivity of platinum(II) diolefin complexes cis-[(vertical bar(perpendicular to)vertical bar)PtCl2], cis-[(vertical bar(perpendicular to)vertical bar)PtCl(R)] and cis-[(vertical bar(perpendicular to)vertical bar)Pt(R)(2)] [vertical bar(perpendicular to)vertical bar = chelate diolefin ligand: 1,5-cyclooctadiene (COD), 1,5-dimethylocta-1,5-diene (Me2COD), norbornadiene (NBD), 1,5-hexadiene (HEX), 3-allyloxypropene (All(2)O, diallyl ether), diallylamine (All(2)NH); R = Me, Bn, C6F5, C6F4H-4 (or -5), or CC(4-Me)Ph] have been explored. The relative exchange rates of the cis-[(vertical bar(perpendicular to)vertical bar)PtCl2] complexes towards the diimine ligand diisopropyl-1,4-diazabutadiene (iPr-DAB) increased along the series COD< Me2COD< NBD< HEX< All(2)O by a factor of 4. The presumably dimeric complex [(All(2)NH)PtCl2](2) undergoes a unique rearrangement process in dimethyl sulfoxide (DMSO) solution to yield the dimeric piperazine complex [PtCl(dmso)(C6H10N)](2), which has been characterised by single-crystal XRD. For selected platinum complexes, cytotoxic effects in HT-29 colon carcinoma and MCF-7 breast cancer cell lines were evaluated. For comparison, the dicationic complexes [(COD)Pt(Bn)(L)][PF6](2) with the very labile coligands N-methyl-4,4-bipyridinium (MQ(+)) and N-methyl-1,4-pyrazinium (Mpz(+)) were added to the study. Although the hexadiene complexes [(HEX)Pt(C6F4H-4)(2)] and [(HEX)Pt(C6F4H-5)(2)] show strong cytotoxicity, the introduction of labile diolefin ligands or the labile cationic MQ(+) or Mpz(+) coligands does not generally lead to markedly increased cytotoxicity

Field-induced compensation of magnetic exchange as the possible origin of reentrant superconductivity in UTe2

International audienceAbstract The potential spin-triplet heavy-fermion superconductor UTe 2 exhibits signatures of multiple distinct superconducting phases. For field aligned along the b axis, a metamagnetic transition occurs at μ 0 H m ≈ 35 T. It is associated with magnetic fluctuations that may be beneficial for the field-reinforced superconductivity surviving up to H m . Once the field is tilted away from the b towards the c axis, a reentrant superconducting phase emerges just above H m . In order to better understand this remarkably field-resistant superconducting phase, we conducted magnetic-torque and magnetotransport measurements in pulsed magnetic fields. We determine the record-breaking upper critical field of μ 0 H c2 ≈ 73 T and its evolution with angle. Furthermore, the normal-state Hall effect experiences a drastic suppression indicative of a reduced band polarization above H m in the angular range around 30° caused by a partial compensation between the applied field and an exchange field. This promotes the Jaccarino-Peter effect as a likely mechanism for the reentrant superconductivity above H m