Research informational site · ute2.ai / ute2.si

Uranium ditelluride (UTe₂)

An orthorhombic heavy-fermion compound that becomes superconducting near 1.6–2.1 K. Claims of spin-triplet pairing, huge upper critical fields, field-reentrant and high-field “halo” phases, and topological superconductivity are active research topics—not settled facts. This site summarizes what primary papers actually report, and where they disagree.

~1.6–2.1 KTc (CVT → MSF)
>40–73 Textreme Hc2 / SCFP
Immmorthorhombic, centrosymmetric
contestedTRSB / chirality

Start with the open questions

Crystal structure & growth

Immm structure to 2.7 K; CVT vs molten-salt flux; why sample quality rewrote conclusions.

Phase diagram

Ambient SC, metamagnetism ~34–35 T, field-reentrant SC, high-field halo, pressure.

Pairing symmetry

Odd-parity evidence, Knight shift, Josephson selection rules, full-gap vs nodes.

TRS & chirality

Hayes Kerr vs Ajeesh null result; μSR; what “chiral” claims still stand on.

STM & spectroscopy

Step-edge states, PDW, microwave, thermal conductivity debates.

Topology & quantum computing

Weyl/Majorana proposals vs what has been measured. No qubit demonstration.

Groups & methods

Where crystals and high-field data come from; how methods bias conclusions.

What is solid vs contested

Comparatively solid

  • Bulk superconductivity near 1.6 K (early CVT) up to ~2.1 K (MSF), independently found in 2019.
  • Extremely large, anisotropic upper critical fields, far beyond the simple Pauli limit for Tc~1.6 K.
  • No magnetic order in the ambient normal state down to Tc; strong ferromagnetic fluctuations along a.
  • Crystal structure remains Immm through the superconducting regime (neutron diffraction to 2.7 K).
  • Sample quality (U vacancies, residual γ, RRR) strongly affects Tc, residual heat capacity, and some “exotic” signals.

Actively contested

  • Intrinsic time-reversal symmetry breaking / chiral order at ambient pressure (Kerr disagreement).
  • Whether ambient-pressure double specific-heat transitions are multicomponent order or inhomogeneity.
  • Full gap (Au-like) vs point nodes, depending on crystal quality and probe.
  • Precise irreducible representation (B1u, Au, multicomponent nonunitary…).
  • Any near-term topological quantum-computing utility (none demonstrated).
UTe2 single crystals from NIST
UTe₂ single crystals (NIST public-domain image). Early discovery crystals were CVT-grown; later MSF crystals reach Tc≈2.1 K with much smaller residual specific heat.

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