| 1. |
- Benito Llorens, José, et al.
(författare)
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Anisotropic superconductivity in the spin-vortex antiferromagnetic superconductor CaK(Fe0.95Ni0.05)4As4
- 2021
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Ingår i: Physical Review B. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 103:6
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Tidskriftsartikel (refereegranskat)abstract
- High critical temperature superconductivity often occurs in systems where an antiferromagnetic order is brought near T=0 K by slightly modifying pressure or doping. CaKFe4As4 is a superconducting, stoichiometric iron-pnictide compound showing optimal superconducting critical temperature with Tc as large as 35 K. Doping with Ni induces a decrease in Tc and the onset of spin-vortex crystal (SVC) antiferromagnetic order, which consists of spins pointing inwards to or outwards from alternating As sites on the diagonals of the in-plane square Fe lattice. Here we study the band structure of CaK(Fe0.95Ni0.05)4As4 (Tc=10 K, TSVC=50 K) using quasiparticle interference with a scanning tunneling microscope and show how the SVC modifies the band structure and induces a fourfold superconducting gap anisotropy.
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| 2. |
- Herrera, Edwin, et al.
(författare)
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Quantum-well states at the surface of a heavy-fermion superconductor
- 2023
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Ingår i: Nature. - : Springer Nature. - 0028-0836 .- 1476-4687. ; 616:7957, s. 465-469
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Tidskriftsartikel (refereegranskat)abstract
- Two-dimensional electronic states at surfaces are often observed in simple wide-band metals such as Cu or Ag (refs. (1-4)). Confinement by closed geometries at the nanometre scale, such as surface terraces, leads to quantized energy levels formed from the surface band, in stark contrast to the continuous energy dependence of bulk electron bands(2,5-10). Their energy-level separation is typically hundreds of meV (refs. (3,6,11)). In a distinct class of materials, strong electronic correlations lead to so-called heavy fermions with a strongly reduced bandwidth and exotic bulk ground states(12,13). Quantum-well states in two-dimensional heavy fermions (2DHFs) remain, however, notoriously difficult to observe because of their tiny energy separation. Here we use millikelvin scanning tunnelling microscopy (STM) to study atomically flat terraces on U-terminated surfaces of the heavy-fermion superconductor URu2Si2, which exhibits a mysterious hidden-order (HO) state below 17.5 K (ref. (14)). We observe 2DHFs made of 5f electrons with an effective mass 17 times the free electron mass. The 2DHFs form quantized states separated by a fraction of a meV and their level width is set by the interaction with correlated bulk states. Edge states on steps between terraces appear along one of the two in-plane directions, suggesting electronic symmetry breaking at the surface. Our results propose a new route to realize quantum-well states in strongly correlated quantum materials and to explore how these connect to the electronic environment.
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| 3. |
- Martin-Vega, Francisco, et al.
(författare)
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Superconducting density of states and band structure at the surface of the candidate topological superconductor Au2Pb
- 2022
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Ingår i: Physical Review Research. - : American Physical Society. - 2643-1564. ; 4:2
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Tidskriftsartikel (refereegranskat)abstract
- The electronic band structure of Au2Pb has a Dirac cone which gaps when undergoing a structural transition into a low temperature superconducting phase. This suggests that the superconducting phase (T-c = 1.1 K) might hold topological properties at the surface. Here we make Scanning Tunneling Microscopy experiments on the surface of superconducting Au2Pb. We measure the superconducting gap and find a sizable superconducting density of states at the Fermi level. We discuss possible origins for this finding in terms of superconductivity induced into surface states.
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| 4. |
- Medina-Dols, Aina, et al.
(författare)
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Role of PATJ in stroke prognosis by modulating endothelial to mesenchymal transition through the Hippo/Notch/PI3K axis
- 2024
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Ingår i: Cell Death Discovery. - : Springer Nature. - 2058-7716. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Through GWAS studies we identified PATJ associated with functional outcome after ischemic stroke (IS). The aim of this study was to determine PATJ role in brain endothelial cells (ECs) in the context of stroke outcome. PATJ expression analyses in patient's blood revealed that: (i) the risk allele of rs76221407 induces higher expression of PATJ, (ii) PATJ is downregulated 24 h after IS, and (iii) its expression is significantly lower in those patients with functional independence, measured at 3 months with the modified Rankin scale ((mRS) <= 2), compared to those patients with marked disability (mRS = 4-5). In mice brains, PATJ was also downregulated in the injured hemisphere at 48 h after ischemia. Oxygen-glucose deprivation and hypoxia-dependent of Hypoxia Inducible Factor-1 alpha also caused PATJ depletion in ECs. To study the effects of PATJ downregulation, we generated PATJ-knockdown human microvascular ECs. Their transcriptomic profile evidenced a complex cell reprogramming involving Notch, TGF-ss, PI3K/Akt, and Hippo signaling that translates in morphological and functional changes compatible with endothelial to mesenchymal transition (EndMT). PATJ depletion caused loss of cell-cell adhesion, upregulation of metalloproteases, actin cytoskeleton remodeling, cytoplasmic accumulation of the signal transducer C-terminal transmembrane Mucin 1 (MUC1-C) and downregulation of Notch and Hippo signaling. The EndMT phenotype of PATJ-depleted cells was associated with the nuclear recruitment of MUC1-C, YAP/TAZ, beta-catenin, and ZEB1. Our results suggest that PATJ downregulation 24 h after IS promotes EndMT, an initial step prior to secondary activation of a pro-angiogenic program. This effect is associated with functional independence suggesting that activation of EndMT shortly after stroke onset is beneficial for stroke recovery.
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| 5. |
- Soda, Minoru, et al.
(författare)
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Penetration Depth and Coherence Length in the Superconductor β-PdBi2
- 2022
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Ingår i: Journal of the Physical Society of Japan. - 1347-4073. ; 91:3
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Tidskriftsartikel (refereegranskat)abstract
- Small angle neutron scattering experiments have been carried out in the mixed state to determine the values and anisotropy of the penetration depth and coherence length in the superconductor β-PdBi2. The distortion of the vortex lattice observed on changing the magnetic field direction suggests that the a–c anisotropy of penetration depth in β-PdBi2 is small. With the magnetic field applied along the c-axis, we estimated the magnitudes of the penetration depth and coherence length by analyzing the magnetic field dependence of the neutron scattering intensity from the vortex lattice. The estimated superconductor parameters are consistent with the upper critical field obtained from the magnetization measurement.
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