Translational symmetry breaking in fluid is antagonistic but can be realized insuperconductivity, which is quantum-mechanical coherent fluid formed byelectron pairs. This novel superconducting state, known as the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state, can be induced by time-reversal-symmetrybreaking magnetic field applied to spin-singlet superconductors. This stateintrinsically causes the superconducting spin smecticity, spin-density-modulatedfluidity with spontaneous translational-symmetry breaking. Detection of suchspin smecticity provides indisputable evidence for the FFLO state but itsobservation has been quite challenging. Here, we report the characteristic“double-horn” nuclear-magnetic-resonance spectrum in the layeredsuperconductor Sr2RuO4 near its upper critical field, indicating the spatialsinusoidal modulation of spin density, namely the superconducting spinsmecticity. Our work reveals that Sr2RuO4 is an ideal compound for studyingthe FFLO physics.
These findings are published in 22nd Apr. 2022 in Science.
“Superconducting spin smecticity evidencing the Fulde-Ferrell-Larkin-Ovchinnikov state in Sr2RuO4”
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