Superconducting spin reorientation in spin-triplet multiple superconducting phases of UTe
            <sub>2</sub>

Kinjo, Katsuki; Fujibayashi, Hiroki; Matsumura, Hiroki; Hori, Fumiya; Kitagawa, Shunsaku; Ishida, K.; Tokunaga, Y.; Sakai, Hironori; Kambe, S.; Nakamura, Ai; Shimizu, Yusei; Homma, Yoshiya; Li, Dexin; Honda, Fuminori; Aoki, Dai

doi:10.1126/sciadv.adg2736

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Kinjo

2024

Springer Theses

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Theoretical Studies on Off-Axis Phase Diagrams and Knight Shifts in UTe$$_2$$: Tetra-Critical Point, d-Vector Rotation, and Multiple Phases

Machida

2024

J Low Temp Phys

1

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Inspired by recent remarkable sets of experiments on UTe$$_2$$ 2 : discoveries of the fourth horizontal internal transition line running toward a tetra-critical point (TCP) at H = 15 T, the off-axis high-field phases, and abnormally large Knight shift (KS) drop below $$T_\textrm{c}$$ T c for $$H \parallel a$$ H ‖ a -magnetic easy axis, we advance further our theoretical work on the field (H)-temperature (T) phase diagram for $$H \parallel b$$ H ‖ b -magnetic hard axis which contains a positive sloped $$H_\textrm{c2}$$ H c2 departing from TCP. A nonunitary spin-triplet pairing with three components explains these experimental facts simultaneously and consistently by assuming that the underlying normal electron system with a narrow bandwidth characteristic to the Kondo temperature $$\sim$$ ∼ 30 K unsurprisingly breaks the particle-hole symmetry. This causes a special invariant term in Ginzburg–Landau (GL) free energy functional which couples directly with the 5f magnetic system, giving rise to the $$T_\textrm{c}$$ T c splitting and ultimately to the positive sloped $$H_\textrm{c2}$$ H c2 and the horizontal internal transition line connected to TCP. The large KS drop can be understood in terms of this GL invariance whose coefficient is negative and leads to a diamagnetic response where the Cooper pair spin is antiparallel to the applied field direction. The present scenario also accounts for the observed d-vector rotation phenomena and off-axis phase diagrams with extremely high $$H_\textrm{c2}$$ H c2 $$\gtrsim$$ ≳ 70 T found at angles in between the b- and c-axes and between the bc-plane and a-axis, making UTe$$_2$$ 2 a fertile playground for a possible topological superconductor.

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Enhanced triplet superconductivity in next-generation ultraclean UTe ₂

Wu,

Weinberger,

Chen

et al. 2024

Proc. Natl. Acad. Sci. U.S.A.

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The unconventional superconductor UTe 2 exhibits numerous signatures of spin-triplet superconductivity—a rare state of matter which could enable quantum computation protected against decoherence. UTe 2 possesses a complex phase landscape comprising two magnetic field-induced superconducting phases, a metamagnetic transition to a field-polarized state, along with pair- and charge-density wave orders. However, contradictory reports between studies performed on UTe 2 specimens of varying quality have severely impeded theoretical efforts to understand the microscopic origins of the exotic superconductivity. Here, we report a comprehensive suite of high magnetic field measurements on a generation of pristine quality UTe 2 crystals. Our experiments reveal a significantly revised high magnetic field superconducting phase diagram in the ultraclean limit, showing a pronounced sensitivity of field-induced superconductivity to the presence of crystalline disorder. We employ a Ginzburg–Landau model that excellently captures this acute dependence on sample quality. Our results suggest that in close proximity to a field–induced metamagnetic transition the enhanced role of magnetic fluctuations—that are strongly suppressed by disorder—is likely responsible for tuning UTe 2 between two distinct spin-triplet superconducting phases.

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Superconducting spin reorientation in spin-triplet multiple superconducting phases of UTe ₂

Cited by 9 publications

References 44 publications

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Results

Theoretical Studies on Off-Axis Phase Diagrams and Knight Shifts in UTe$$_2$$: Tetra-Critical Point, d-Vector Rotation, and Multiple Phases

Enhanced triplet superconductivity in next-generation ultraclean UTe ₂

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Superconducting spin reorientation in spin-triplet multiple superconducting phases of UTe 2

Cited by 9 publications

References 44 publications

Results

Results

Theoretical Studies on Off-Axis Phase Diagrams and Knight Shifts in UTe$$_2$$: Tetra-Critical Point, d-Vector Rotation, and Multiple Phases

Enhanced triplet superconductivity in next-generation ultraclean UTe 2

Contact Info

Product

Resources

About

Superconducting spin reorientation in spin-triplet multiple superconducting phases of UTe ₂

Enhanced triplet superconductivity in next-generation ultraclean UTe ₂