Non-Trivial Superconductivity in the Semimetal EuAuBi
© The Physical Society of Japan
This article is on
Superconductivity in a Magnetic Rashba Semimetal EuAuBi
(JPSJ Editors' Choice)
J. Phys. Soc. Jpn. 92, 013701 (2023).
Magnetic order and superconductivity coexist in a noncentrosymmetric topological semimetal, EuAuBi. EuAuBi exhibits a large, anisotropic critical field with Rashba spin–orbit coupling, which can help develop superconducting spintronic materials.

In conventional s-wave superconductivity described by the Bardeen–Cooper–Schrieffer (BCS) theory, superconducting Cooper pairs are mediated by phonons, and these pairs (spin singlet) exhibit time-reversal and space-inversion symmetries. Therefore, magnetism and polarity that break these symmetries are generally incompatible with s-wave superconductivity. By contrast, superconductivity in systems without time-reversal and space-inversion symmetry has recently attracted attention as unconventional superconductivity. In particular, systems without space inversion symmetry exhibit a mixture of singlet and triplet pairing states. Furthermore, topological materials with surface states demonstrate spatial inversion symmetry breaking at the crystal interface, thereby providing a possibility for developing materials with unusual surface superconductivity.
In this study, we successfully synthesized a single crystal of the topological semimetal EuAuBi, which has a layered structure comprising magnetic Eu triangle and conducting Au-Bi honeycomb layers. The synthesized crystal demonstrated antiferromagnetic and superconducting transitions at 4 and 2.4 K, respectively. The polar structure of this material is responsible for the alternating displacement of Au and Bi ions, resulting in a unique system that exhibits magnetic ordering and superconductivity with a polar structure.
To investigate the superconducting properties of this material, changes in the superconducting transition temperature were measured down to as low as 0.1 K by applying an in-plane and an inter-plane magnetic field. Consequently, a superconducting critical field of 10 T, considerably greater than the Pauli limit expected for conventional superconductivity, was observed in the inter-plane field, while the critical field was only 3 T in the in-plane field. First-principles calculations revealed that Rashba spin splitting and a topological band structure are realized owing to the polar structure and strong spin–orbit coupling of Bi p orbitals. Therefore, the large critical field above the Pauli limit and its anisotropy may reflect a Rashba-type band structure and surface superconductivity, suggesting the realization of unconventional superconductivity.
For the first time, we unveiled superconducting properties in the topological semimetal EuAuBi, which exhibits magnetic order and polar structure. The coexistence of large magnetization and superconductivity in this system may accelerate the development of spintronic materials that exhibit a novel external field response.
(written by H. Takahashi on behalf of all the authors. )
Superconductivity in a Magnetic Rashba Semimetal EuAuBi
(JPSJ Editors' Choice)
J. Phys. Soc. Jpn. 92, 013701 (2023).
Share this topic
Fields
Related Articles
-
Antisymmetric Exchange Interaction Selects the Cycloidal Helicity: Observation by Resonant X-ray Diffraction
Magnetic properties in condensed matter
2023-9-5
The unique sense of rotation of the cycloidal magnetic order was clarified in noncentrosymmetric EuIrGe3 by using circularly polarized resonant x-ray diffraction.
-
Exploring Vortex Dynamics in a Multi-band Superconductor
Superconductivity
2023-8-22
We measured the microwave flux-flow Hall effect in FeSe, where the cancellation of holes and electrons was observed. This is a novel effect of multi-band superconductors.
-
Double Superconductivity in Nodal Line Material NaAlSi; Coexistence of Bulk and 2D Superconductivities
Superconductivity
Electronic structure and electrical properties of surfaces and nanostructures
2023-7-26
Unique diamagnetic torque signals are found in the nodal line material NaAlSi, which suggests the presence of double superconductivity; i.e., bulk superconductivity and 2D superconductivity on the crystal surface.
-
Self-Energy Singularity Explains High-Temperature Superconductivity in Cuprates
Superconductivity
Electron states in condensed matter
2023-7-18
A new review discusses the high-temperature superconductivity mechanisms in copper oxides, explaining the various phases observed in these materials based on a nonperturbative effect called self-energy singularity.
-
Ultra Purification Unveils the Intrinsic Nature in Spin-Triplet Superconductor UTe2
Superconductivity
Magnetic properties in condensed matter
2023-7-5
Microscopic spin-susceptibility measurements in ultra-pure UTe2 samples reveal that superconducting symmetry is analogous to the superfluidity of the 3He B-phase and that U deficiency has a significant impact on superconducting properties.