Bulk signal in a symmetric crystal
Te-doped PtBi2 single crystals showed evidence of superconductivity across the selected samples, with a reported superconducting volume fraction of about 100% and a bulk transition near 2.4 K. Single-crystal X-ray diffraction identified the centrosymmetric P 3m1 space group, a structure with inversion symmetry. Here, bulk means the superconducting response was reported in magnetization and specific-heat measurements of the crystal, rather than only in a local electrical contact. The combination of a bulk transition and a centrosymmetric structure is the central finding of the report.
One composition became the focus
The researchers grew a stoichiometric-melt series of Te-doped PtBi2-xTex crystals at x values of 0, 0.02, 0.03, 0.04 and 0.05. The selected nominal composition was PtBi1.96Te0.04, corresponding to x = 0.04 in that series. One same-batch crystal was used for magnetization, heat-capacity, resistance, point-contact and EDS measurements. Two different crystals from the same batch were used for single-crystal X-ray diffraction and ARPES because of size and cleaving constraints.
The chemistry is not fully settled
The nominal formula did not settle the sample's exact chemistry. EDS measured the Pt:Bi:Te composition as 37.45:61.33:1.22 atomic percent. A second technique, ICP-OES, gave 35.6:63.0:1.4 atomic percent. Both measurements indicated a deficiency of combined Bi plus Te relative to Pt. The ICP-OES result put the Bi-plus-Te to Pt ratio near 1.81, while the Te-to-Bi ratio was about 0.02, close to the expected proportion. The physical source of the deficiency remained unresolved.
Three measurements point to the same transition
Heat capacity found a second-order superconducting anomaly with a midpoint temperature of 2.3 K, and a 2 kOe field completely removed the anomaly. That value is close to, but slightly below, the report's bulk transition estimate of about 2.4 K from magnetization and specific-heat measurements. A heat-capacity fit gave gamma = 4.3(3) mJ/mol K2, beta = 2.35(5) mJ/mol K4 and a Debye temperature of about 135 K. The estimated heat-capacity jump ratio was about 2.1, which the authors said hinted at strong-coupling superconductivity.
Electrical and magnetic tests add detail
Resistance measurements supplied a separate transition at Tc rho = 2.40 K, using a 50% resistivity criterion. Between fields of 0 and 2.4 kOe, the zero-field transition was sharp, then broadened and shifted to lower temperature as the field increased. The normal-state resistivity was about 135 micro-ohm cm, and the residual-resistivity ratio was about 1.1.
The upper critical field, the field scale used to describe the suppression of superconductivity, was extrapolated to about 6.3 kOe for a field in the plane and 4.7 kOe for a field out of the plane. The authors interpret the material as a type-II superconductor with low critical-field anisotropy, about 1.3.
Local contacts gave a higher, less uniform result
Measurements through point contacts gave a different and more variable set of transition temperatures. Across all measured contacts, the average Tc was 3.1 K, with a standard deviation of 0.8 K. The largest observed value was about 5 K, and the critical field reached up to 4 T. The enhancement varied with the contact and counterelectrode, and the report calls for additional statistics from contacts made with cobalt tips.
Because the higher values varied from contact to contact, they do not by themselves establish an intrinsic bulk transition above the approximately 2.4 K result from magnetization and heat capacity. The point-contact measurements are therefore best read as evidence of a local, contact-dependent effect that needs further testing.
A surface without Fermi arcs
Surface-sensitive ARPES measurements found a single surface termination and no Fermi arcs in the Te-doped compound. These observations describe the surface electronic structure measured in the experiment, but they do not directly determine the superconducting pairing symmetry. The authors' interpretation is correspondingly focused on bulk superconductivity in the centrosymmetric phase, rather than on a specific pairing state inferred from the ARPES result.
What the preprint leaves open
Taken together, the measurements present a consistent materials picture at the selected composition: X-ray diffraction reports the centrosymmetric P 3m1 structure, magnetic and heat-capacity measurements report roughly complete superconducting volume near 2.4 K, resistance shows a 2.40 K transition, and the upper critical fields show only modest orientation dependence. But the study does not isolate Te substitution from the measured Bi-plus-Te deficiency, and it does not establish that the higher point-contact temperatures are intrinsic bulk properties.
The detailed superconducting evidence centers on the nominal PtBi1.96Te0.04 composition, while structural and ARPES measurements were made on two other same-batch crystals. The work is identified as arXiv:2608.25093v1, dated 25 August 2026, so the supplied record describes it as a preprint rather than a completed journal publication.
Paper data and sources
Original title: Probing bulk superconductivity in centrosymmetric Te-doped PtBi$_2$ single crystals
Authors: Kilian Srowik, Pablo Pedrazzini, Soumen Ash et al.
Journal/Repository: arXiv
Status: Preprint, not yet peer-reviewed
First online: 2026-08-25
DOI: Not available
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