Origin of a shallow electron pocket: $β$-band in Co$_{1/3}$TaS$_2$ studied by angle-resolved photoemission spectroscopy
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2026
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| author | Sas, Wojciech Boucher, Yuki Utsumi Ziabari, Seyed Ashkan Moghadam Pransu, Gaurav Ivšić, Trpimir Vobornik, Ivana Fujii, Jun Dhami, Naveen Singh Gudac, Bruno Novak, Mario Forró, László Barišić, Neven Batistić, Ivo Popčević, Petar |
| author_facet | Sas, Wojciech Boucher, Yuki Utsumi Ziabari, Seyed Ashkan Moghadam Pransu, Gaurav Ivšić, Trpimir Vobornik, Ivana Fujii, Jun Dhami, Naveen Singh Gudac, Bruno Novak, Mario Forró, László Barišić, Neven Batistić, Ivo Popčević, Petar |
| contents | We investigate the electronic structure and Fermi surface of Co$_{1/3}$TaS$_2$ using angle-resolved photoemission spectroscopy (ARPES) combined with theoretical modeling beyond standard density functional theory (DFT+U). A shallow electron pocket, the so-called $β$ feature, is observed at the Fermi level near the corner of the superlattice Brillouin zone, representing the first experimental observation of this feature in an intercalated TaS$_2$ compound. Similar pockets have been reported in $X_{1/3}$NbS$_2$ ($X$ = Co, Cr, Ni), where their surface versus bulk origin remains actively debated. Because conventional DFT+U does not capture this feature, we employ cluster perturbation theory (CPT) to incorporate an explicit treatment of strong electron correlations ($U$) on the Co sites. CPT successfully reproduces the $β$ feature, demonstrating its origin from correlation-driven bulk states rather than surface effects. To further substantiate this conclusion, we studied a reduced Co-content sample, Co$_{0.22}$TaS$_2$, where the reduced charge transfer modifies the Co-derived states near the Fermi level. Its electronic structure remains largely similar to that of pristine 2H-TaS$_2$, showing only a minor overall energy shift and lacking the $β$ feature, consistent with disrupted long-range Co ordering and modified orbital character near the Fermi level. We demonstrate that the $β$ feature arises from strong local correlations on the Co sites and requires long-range crystallographic order among intercalated Co atoms to maintain coherence. These results highlight the importance of strong electronic correlations in magnetically intercalated transition-metal dichalcogenides and provide a microscopic understanding of features not captured by conventional DFT+U. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2602_15588 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Origin of a shallow electron pocket: $β$-band in Co$_{1/3}$TaS$_2$ studied by angle-resolved photoemission spectroscopy Sas, Wojciech Boucher, Yuki Utsumi Ziabari, Seyed Ashkan Moghadam Pransu, Gaurav Ivšić, Trpimir Vobornik, Ivana Fujii, Jun Dhami, Naveen Singh Gudac, Bruno Novak, Mario Forró, László Barišić, Neven Batistić, Ivo Popčević, Petar Strongly Correlated Electrons We investigate the electronic structure and Fermi surface of Co$_{1/3}$TaS$_2$ using angle-resolved photoemission spectroscopy (ARPES) combined with theoretical modeling beyond standard density functional theory (DFT+U). A shallow electron pocket, the so-called $β$ feature, is observed at the Fermi level near the corner of the superlattice Brillouin zone, representing the first experimental observation of this feature in an intercalated TaS$_2$ compound. Similar pockets have been reported in $X_{1/3}$NbS$_2$ ($X$ = Co, Cr, Ni), where their surface versus bulk origin remains actively debated. Because conventional DFT+U does not capture this feature, we employ cluster perturbation theory (CPT) to incorporate an explicit treatment of strong electron correlations ($U$) on the Co sites. CPT successfully reproduces the $β$ feature, demonstrating its origin from correlation-driven bulk states rather than surface effects. To further substantiate this conclusion, we studied a reduced Co-content sample, Co$_{0.22}$TaS$_2$, where the reduced charge transfer modifies the Co-derived states near the Fermi level. Its electronic structure remains largely similar to that of pristine 2H-TaS$_2$, showing only a minor overall energy shift and lacking the $β$ feature, consistent with disrupted long-range Co ordering and modified orbital character near the Fermi level. We demonstrate that the $β$ feature arises from strong local correlations on the Co sites and requires long-range crystallographic order among intercalated Co atoms to maintain coherence. These results highlight the importance of strong electronic correlations in magnetically intercalated transition-metal dichalcogenides and provide a microscopic understanding of features not captured by conventional DFT+U. |
| title | Origin of a shallow electron pocket: $β$-band in Co$_{1/3}$TaS$_2$ studied by angle-resolved photoemission spectroscopy |
| topic | Strongly Correlated Electrons |
| url | https://arxiv.org/abs/2602.15588 |