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1. Tuning magnetic confinement of spin-triplet superconductivity

   https://doi.org/10.1038/s41535-020-00270-w  

   Lin, Wen-Chen; Campbell, Daniel J.; Ran, Sheng; Liu, I-Lin; Kim, Hyunsoo; Nevidomskyy, Andriy H.; Graf, David; Butch, Nicholas P.; Paglione, Johnpierre (December 2020, npj Quantum Materials)

   null (Ed.)

   Abstract Electrical magnetoresistance and tunnel diode oscillator measurements were performed under external magnetic fields up to 41 T applied along the crystallographic b axis (hard axis) of UTe 2 as a function of temperature and applied pressures up to 18.8 kbar. In this work, we track the field-induced first-order transition between superconducting and magnetic field-polarized phases as a function of applied pressure, showing suppression of the transition with increasing pressure until the demise of superconductivity near 16 kbar and the appearance of a pressure-induced ferromagnetic-like ground state that is distinct from the field-polarized phase and stable at zero field. Together with evidence for the evolution of a second superconducting phase and its upper critical field with pressure, we examine the confinement of superconductivity by two orthogonal magnetic phases and the implications for understanding the boundaries of triplet superconductivity. 

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2. Odd-parity quasiparticle interference in the superconductive surface state of UTe2

   https://doi.org/10.1038/s41567-025-03000-w  

   Wang, Shuqiu; Zhussupbekov, Kuanysh; Carroll, Joseph P; Hu, Bin; Liu, Xiaolong; Pangburn, Emile; Crepieux, Adeline; Pepin, Catherine; Broyles, Christopher; Ran, Sheng; et al (October 2025, Nature Physics)

   Abstract Although no known material exhibits intrinsic topological superconductivity, where a spin-triplet electron pairing potential has odd parity, UTe₂is now the leading candidate. Generally, the parity of a superconducting order parameter can be established using Bogoliubov quasiparticle interference imaging. However, odd-parity superconductors should support a topological quasiparticle surface band at energies within the maximum superconducting energy gap. Quasiparticle interference should then be dominated by the electronic structure of the quasiparticle surface band and only reveal the characteristics of the bulk order parameter indirectly. Here we demonstrate that at the (0–11) cleave surface of UTe₂, a band of Bogoliubov quasiparticles appears only in the superconducting state. Performing high-resolution quasiparticle interference measurements then allows us to explore the dispersion of states in this superconductive surface band, showing that they exist only within the range of Fermi momenta projected onto the (0–11) surface. Finally, we develop a theoretical framework to predict the quasiparticle interference signatures of this surface band at the (0–11) surface. Its predictions are consistent with the experimental results if the bulk superconducting order parameter exhibits time-reversal conserving, odd-parity,a-axis nodal,B_3usymmetry. 

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3. Giant transverse magnetic fluctuations at the edge of re-entrant superconductivity in UTe2

   https://doi.org/10.1038/s41467-026-71899-7  

   Zambra, Valeska; Nathwani, Amit; Nauman, Muhammad; Lewin, Sylvia K; Frank, Corey E; Butch, Nicholas P; Shekhter, Arkady; Ramshaw, B J; Modic, K A (April 2026, Nature Communications)

   Abstract UTe₂exhibits the remarkable phenomenon of re-entrant superconductivity, whereby the zero-resistance state reappears above 40 tesla after being suppressed with a field of around 10 tesla. One potential pairing mechanism, invoked in the related re-entrant superconductors UCoGe and URhGe, involves transverse fluctuations of a ferromagnetic order parameter. However, the requisite ferromagnetic order—present in both UCoGe and URhGe—is absent in UTe₂, and neutron scattering shows instead that the magnetic susceptibility is peaked at an antiferromagnetic wavevector. Here, we measure the magnetotropic susceptibility of UTe₂across two field-angle planes. This quantity is sensitive to the magnetic susceptibility in a direction transverse to the applied magnetic field—a quantity that is not accessed in conventional magnetization measurements. We observe a very large decrease in the magnetotropic susceptibility over a broad range of field orientations, indicating a large increase in the transverse magnetic susceptibility. Because our technique probes the magnetic susceptibility in the long wavelength (q = 0) limit, this suggests that the strong transverse susceptibility arises from ferromagnetic spin fluctuations. These ferromagnetic fluctuations are likely important for understanding the pairing mechanism in UTe₂, as all three superconducting phases of UTe₂surround this region of enhanced susceptibility in the field-angle phase diagram. 

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4. Orphan high field superconductivity in non-superconducting uranium ditelluride

   https://doi.org/10.1038/s41467-024-47090-1  

   Frank, Corey E.; Lewin, Sylvia K.; Saucedo Salas, Gicela; Czajka, Peter; Hayes, Ian M.; Yoon, Hyeok; Metz, Tristin; Paglione, Johnpierre; Singleton, John; Butch, Nicholas P. (April 2024, Nature Communications)

   Abstract Reentrant superconductivity is an uncommon 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 superconducting phase. Here, we show that in UTe₂crystals extreme applied magnetic fields give rise to an unprecedented high-field superconductor that lacks a zero-field antecedent. This high-field orphan superconductivity exists at angles offset between 29^oand 42^ofrom the crystallographicbtocaxes with applied fields between 37 T and 52 T. The stability of field-induced orphan superconductivity presented in this work defies both empirical precedent and theoretical explanation and demonstrates that high-field superconductivity can exist in an otherwise non-superconducting material. 

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5. Asymmetric phase diagram and dimensional crossover in a system of spin- $\frac{1}{2}$ dimers under applied hydrostatic pressure

   https://doi.org/10.1103/PhysRevB.108.224431  

   Coak, M J; Curley, S_P M; Hawkhead, Z; Tidey, J P; Graf, D; Clark, S J; Sengupta, P; Manson, Z E; Lancaster, T; Goddard, P A; et al (December 2023, Physical Review B)

   Kancharla, S (Ed.)

   We present the magnetic and structural properties of [Cu(pyrazine)0.5(glycine)]ClO4 under applied pressure. As previously reported, at ambient pressure this material consists of quasi-two-dimensional layers of weakly coupled antiferromagnetic dimers which undergo Bose-Einstein condensation of triplet excitations between two magnetic field-induced quantum critical points (QCPs). The molecular building blocks from which the compound is constructed give rise to exchange strengths that are considerably lower than those found in other S = 1/2 dimer materials, which allows us to determine the pressure evolution of the entire field-temperature magnetic phase diagram using radio-frequency magnetometry. We find that a distinct phase emerges above the upper field-induced transition at elevated pressures and also show that an additional QCP is induced at zero field at a critical pressure of pc = 15.7(5) kbar. Pressure-dependent single-crystal x-ray diffraction and density functional theory calculations indicate that this QCP arises primarily from a dimensional crossover driven by an increase in the interdimer interactions between the planes. While the effect of quantum fluctuations on the lower field-induced transition is enhanced with applied pressure, quantum Monte Carlo calculations suggest that this alone cannot explain an unconventional asymmetry that develops in the phase diagram. 

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