Calorimetric evidence for two phase transitions in Calorimetric evidence for two phase transitions in Ba1−xKxFe2As2 with fermion pairing and quadrupling statesNational Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, 305-8568, Japan.
Tsung-Dao Lee Institute, Shanghai Jiao Tong University, Shanghai, 201210, China.
Tsung-Dao Lee Institute, Shanghai Jiao Tong University, Shanghai, 201210, China.
Tsung-Dao Lee Institute, Shanghai Jiao Tong University, Shanghai, 201210, China.
Tsung-Dao Lee Institute, Shanghai Jiao Tong University, Shanghai, 201210, China.
Tsung-Dao Lee Institute, Shanghai Jiao Tong University, Shanghai, 201210, China; School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, 200240, China.
Institute for Metallic Materials, Leibniz-IFW Dresden, D-01069, Dresden, Germany.
Institute for Solid State and Materials Physics, Technische Universität Dresden, D-01069, Dresden, Germany.
University of Genoa, Via Dodecaneso 33, 16146, Genoa, Italy; Consiglio Nazionale delle Ricerche (CNR)-SPIN, Corso Perrone 24, 16152, Genova, Italy.
University of Genoa, Via Dodecaneso 33, 16146, Genoa, Italy; Consiglio Nazionale delle Ricerche (CNR)-SPIN, Corso Perrone 24, 16152, Genova, Italy; Institute for Solid State Research, Leibniz-IFW Dresden, D-01069, Dresden, Germany.
Tsung-Dao Lee Institute, Shanghai Jiao Tong University, Shanghai, 201210, China; School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, 200240, China.
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2023 (English)In: Nature Communications, E-ISSN 2041-1723, Vol. 14, no 1, article id 6734Article in journal (Refereed) Published
Abstract [en]
Materials that break multiple symmetries allow the formation of four-fermion condensates above the superconducting critical temperature (T c). Such states can be stabilized by phase fluctuations. Recently, a fermionic quadrupling condensate that breaks the Z 2 time-reversal symmetry was reported in Ba1−xKxFe2As2. A phase transition to the new state of matter should be accompanied by a specific heat anomaly at the critical temperature where Z 2 time-reversal symmetry is broken (TcZ2>Tc). Here, we report on detecting two anomalies in the specific heat of Ba1−xKxFe2As2 at zero magnetic field. The anomaly at the higher temperature is accompanied by the appearance of a spontaneous Nernst effect, indicating the breakdown of Z 2 symmetry. The second anomaly at the lower temperature coincides with the transition to a zero-resistance state, indicating the onset of superconductivity. Our data provide the first example of the appearance of a specific heat anomaly above the superconducting phase transition associated with the broken time-reversal symmetry due to the formation of the novel fermion order.
Place, publisher, year, edition, pages
Nature Research , 2023. Vol. 14, no 1, article id 6734
National Category
Condensed Matter Physics Subatomic Physics
Identifiers
URN: urn:nbn:se:kth:diva-339045DOI: 10.1038/s41467-023-42459-0PubMedID: 37872158Scopus ID: 2-s2.0-85174605964OAI: oai:DiVA.org:kth-339045DiVA, id: diva2:1815271
Note
QC 20231128
2023-11-282023-11-282024-02-29Bibliographically approved