| 1. |
- Dhakal, Gyanendra, et al.
(författare)
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Anisotropically large anomalous and topological Hall effect in a kagome magnet
- 2021
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Ingår i: Physical Review B. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 104:16
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Tidskriftsartikel (refereegranskat)abstract
- Recently, kagome materials have become an engrossing platform to study the interplay among symmetry, magnetism, topology, and electron correlation. The latest works on RMn6Sn6 (R = rare-earth metal) compounds have illustrated that this family could be intriguing to investigate various physical phenomena due to large spin-orbit coupling and strong magnetic ordering. However, combined transport and spectroscopic studies in RMn6Sn6 materials are still limited. Here, we report magnetic, magnetotransport, and angle-resolved photoemission spectroscopy measurements of a kagome magnet ErMn6Sn6 that undergoes antiferromagnetic (TN = 345 K) to ferrimagnetic (TC = 68 K) phase transitions in the presence of a field. We observe large anomalous and topological Hall effects serving as transport signatures of the nontrivial Berry curvature. The isothermal magnetization exhibits strong anisotropic nature and the topological Hall effect of the compound depends on the critical field of metamagnetic transition. Our spectroscopic results complemented by theoretical calculations show the multiorbital kagome fermiology. This Letter provides new insight into the tunability and interplay of topology and magnetism in a kagome magnet.
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| 2. |
- Regmi, Sabin, et al.
(författare)
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Observation of multiple nodal lines in SmSbTe
- 2022
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Ingår i: Physical Review Materials. - : American Physical Society. - 2475-9953. ; 6:3
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Tidskriftsartikel (refereegranskat)abstract
- Having been a ground for various topological fermionic phases, the family of ZrSiS-type 111 materials has been under experimental and theoretical investigations. Within this family of materials, the subfamily LnSbTe (Ln = lanthanide elements) is gaining interest in recent times as the strong correlation effects and magnetism arising from the 4f electrons of the lanthanides can provide an important platform to study the link between topology, magnetism, and correlation. In this Letter, we report the systematic study of the electronic structure of SmSbTe-a member of the LnSbTe subfamily-by utilizing angle-resolved photoemission spectroscopy in conjunction with first-principles calculations, transport, and magnetic measurements. Our experimental results identify multiple Dirac nodes forming the nodal lines along the Gamma-X and Z-R directions in the bulk Brillouin zone (BZ) as predicted by our theoretical calculations. A surface Dirac-like state is also observed at the (X) over bar point of the surface BZ. Our study highlights SmSbTe as a promising candidate to understand the topological electronic structure of LnSbTe materials.
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| 3. |
- Schrodi, Fabian, et al.
(författare)
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Exploring multichannel superconductivity in ThFeAsN
- 2021
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Ingår i: Physical Review B. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 104:9
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Tidskriftsartikel (refereegranskat)abstract
- We investigate theoretically the superconducting state of the undoped Fe-based superconductor ThFeAsN. Using input from ab initio calculations, we solve the Fermi-surface based, multichannel Eliashberg equations for Cooper-pair formation mediated by spin and charge fluctuations, and by the electron-phonon interaction (EPI). Our results reveal that spin fluctuations alone, when coupling only hole-like with electron-like energy bands, can account for a critical temperature Tc up to ∼7.5K with an s±-wave superconducting gap symmetry, which is a comparatively low Tc with respect to the experimental value Texpc=30K. Other combinations of interaction kernels (spin, charge, electron-phonon) lead to a suppression of Tc due to phase frustration of the superconducting gap. We qualitatively argue that the missing ingredient to explain the gap magnitude and Tc in this material might be the first-order correction to the EPI vertex. In the noninteracting state this correction adopts a form supporting the s± gap symmetry, in contrast to EPI within Migdal's approximation, i.e., EPI without vertex correction, and therefore it enhances tendencies arising from spin fluctuations.
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| 4. |
- Zhang, Yingchao, et al.
(författare)
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Coherent modulation of the electron temperature and electron-phonon couplings in a 2D material
- 2020
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 117:16, s. 8788-8793
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Tidskriftsartikel (refereegranskat)abstract
- Ultrashort light pulses can selectively excite charges, spins, and phonons in materials, providing a powerful approach for manipulating their properties. Here we use femtosecond laser pulses to coherently manipulate the electron and phonon distributions, and their couplings, in the charge-density wave (CDW) material 1T-TaSe2. After exciting the material with a femtosecond pulse, fast spatial smearing of the laser-excited electrons launches a coherent lattice breathing mode, which in turn modulates the electron temperature. This finding is in contrast to all previous observations in multiple materials to date, where the electron temperature decreases monotonically via electron-phonon scattering. By tuning the laser fluence, the magnitude of the electron temperature modulation changes from similar to 200 K in the case of weak excitation, to similar to 1,000 K for strong laser excitation. We also observe a phase change of pi in the electron temperature modulation at a critical fluence of 0.7 mJ/cm(2), which suggests a switching of the dominant coupling mechanism between the coherent phonon and electrons. Our approach opens up routes for coherently manipulating the interactions and properties of two-dimensional and other quantum materials using light.
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