Topological insulators are characterized by protected gapless surface or edge states but insulating bulk states which is due to the presence of spin-orbit interactions and time-reversal symmetry. Here, an in-depth investigation of a topological nodal line semimetal PbTaSe2 via temperature, polarization dependent Raman spectroscopy, and temperature dependent single crystal X-ray diffraction (SC-XRD) measurements is reported. The analysis shows signature of electron-phonon coupling as reflected in the Fano asymmetry in line shape of M1-M4 modes and anomalous temperature variation of line-width of P3-P4 modes. Further polarization dependent phonon symmetry changes at different temperature (6K and 300K), discontinuities in bulk phonon dynamics for P2-P5 modes, and disappearance of phonon modes, i.e., M1-M5, on decreasing temperature indicates toward a thermally induced structural phase transition which is also supported by the SC-XRD results. Hence based on the findings, it is proposed that M1-M4 modes are surface phonon modes, the material undergoes a thermally induced structural phase transition from α to β phase at Tα→β ≈ 150 K or is in close proximity to the β phase and another transition below TCDW+β ≈ 100K which is possibly due to the interplay of remanent completely commensurate charge density wave (CCDW) of 1H-TaSe2 and β phase.
{"title":"Surface Phonons and Possible Structural Phase Transition in a Topological Semimetal PbTaSe2","authors":"Vivek Kumar, Pradeep Kumar","doi":"10.1002/andp.202400277","DOIUrl":"https://doi.org/10.1002/andp.202400277","url":null,"abstract":"<p>Topological insulators are characterized by protected gapless surface or edge states but insulating bulk states which is due to the presence of spin-orbit interactions and time-reversal symmetry. Here, an in-depth investigation of a topological nodal line semimetal PbTaSe<sub>2</sub> via temperature, polarization dependent Raman spectroscopy, and temperature dependent single crystal X-ray diffraction (SC-XRD) measurements is reported. The analysis shows signature of electron-phonon coupling as reflected in the Fano asymmetry in line shape of M1-M4 modes and anomalous temperature variation of line-width of P3-P4 modes. Further polarization dependent phonon symmetry changes at different temperature (6K and 300K), discontinuities in bulk phonon dynamics for P2-P5 modes, and disappearance of phonon modes, i.e., M1-M5, on decreasing temperature indicates toward a thermally induced structural phase transition which is also supported by the SC-XRD results. Hence based on the findings, it is proposed that M1-M4 modes are surface phonon modes, the material undergoes a thermally induced structural phase transition from α to β phase at T<sub>α→β</sub> ≈ 150 K or is in close proximity to the β phase and another transition below T<sub>CDW+β</sub> ≈ 100K which is possibly due to the interplay of remanent completely commensurate charge density wave (CCDW) of 1H-TaSe<sub>2</sub> and β phase.</p>","PeriodicalId":7896,"journal":{"name":"Annalen der Physik","volume":"537 2","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143389439","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Masthead: Ann. Phys. 11/2024","authors":"","doi":"10.1002/andp.202470026","DOIUrl":"https://doi.org/10.1002/andp.202470026","url":null,"abstract":"","PeriodicalId":7896,"journal":{"name":"Annalen der Physik","volume":"536 11","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/andp.202470026","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142664919","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Negative-Mass Black Holes under Antichronous Transformations
Black hole's gravitational singularities are solved by interior negative energies and masses through time transformations of relativistic quantum mechanics and antichronous transformations of the full Lorentz group, which, if taking place at event horizons, respect Einstein's equivalence principle. For further details, see article number 2400139 by Manuel Uruena Palomo.