| 1. |
- Bonetti, Pietro M., et al.
(författare)
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Interaction-driven first-order and higher-order topological superconductivity
- 2024
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Ingår i: Physical Review B. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 109:18
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Tidskriftsartikel (refereegranskat)abstract
- We investigate topological superconductivity in the Rashba-Hubbard model, describing heavy-atom superlattice and van der Waals materials with broken inversion. We focus in particular on fillings close to the van Hove singularities, where a large density of states enhances the superconducting transition temperature. To determine the topology of the superconducting gaps and to analyze the stability of their surface states in the presence of disorder and residual interactions, we employ an fRG+MFT approach, which combines the unbiased functional renormalization group (fRG) with a real-space mean-field theory (MFT). Our approach uncovers a cascade of topological superconducting states, including ?1 and ?1 pairings, whose wave functions are of dominant ?- and ?-wave character, respectively, as well as a time-reversal breaking ?1+??1 pairing. While the ?1 and ?1 states have first-order topology with helical and flat-band Majorana edge states, respectively, the ?1+??1 pairing exhibits second-order topology with Majorana corner modes. We investigate the disorder stability of the bulk superconducting states, analyze interaction-induced instabilities of the edge states, and discuss implications for experimental systems.
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| 2. |
- Kong, Xiangchen, et al.
(författare)
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Glucagon-Like Peptide 1 Stimulates Insulin Secretion via Inhibiting RhoA/ROCK Signaling and Disassembling Glucotoxicity-Induced Stress Fibers
- 2014
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Ingår i: Endocrinology. - : The Endocrine Society. - 0013-7227 .- 1945-7170. ; 155:12, s. 4676-4685
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Tidskriftsartikel (refereegranskat)abstract
- Chronic hyperglycemia leads to pancreatic beta-cell dysfunction characterized by diminished glucose-stimulated insulin secretion (GSIS), but the precise cellular processes involved are largely unknown. Here we show that pancreatic beta-cells chronically exposed to a high glucose level displayed substantially increased amounts of stress fibers compared with beta-cells cultured at a low glucose level. beta-Cells at high glucose were refractory to glucose-induced actin cytoskeleton remodeling and insulin secretion. Importantly, F-actin depolymerization by either cytochalasin B or latrunculin B restored glucotoxicity-diminished GSIS. The effects of glucotoxicity on increasing stress fibers and reducing GSIS were reversed by Y-27632, a Rho-associated kinase (ROCK)-specific inhibitor, which caused actin depolymerization and enhanced GSIS. Notably, glucagon-like peptide-1-(7-36) amide (GLP-1), a peptide hormone that stimulates GSIS at both normal and hyperglycemic conditions, also reversed glucotoxicity-induced increase of stress fibers and reduction of GSIS. In addition, GLP-1 inhibited glucotoxicity-induced activation of RhoA/ROCK and thereby resulted in actin depolymerization and potentiation of GSIS. Furthermore, this effect of GLP-1 was mimicked by cAMP-increasing agents forskolin and 3-isobutyl-1-methylxanthine as well as the protein kinase A agonist 6-Bnz-cAMP-AM whereas it was abolished by the protein kinase A inhibitor Rp-Adenosine 3',5'-cyclic monophosphorothioate triethylammonium salt. To establish a clinical relevance of our findings, we examined the association of genetic variants of RhoA/ROCK with metabolic traits in homeostasis model assessment index of insulin resistance. Several single-nucleotide polymorphisms in and around RHOA were associated with elevated fasting insulin and homeostasis model assessment index of insulin resistance, suggesting a possible role in metabolic dysregulation. Collectively these findings unravel a novel mechanism whereby GLP-1 potentiates glucotoxicity-diminished GSIS by depolymerizing F-actin cytoskeleton via protein kinase A-mediated inhibition of the RhoA-ROCK signaling pathway.
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| 3. |
- Li, Cong, et al.
(författare)
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Coexistence of two intertwined charge density waves in a kagome system
- 2022
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Ingår i: Physical Review Research. - : American Physical Society (APS). - 2643-1564. ; 4:3
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Tidskriftsartikel (refereegranskat)abstract
- Materials with a kagome lattice structure display a wealth of intriguing magnetic properties due to their geometric frustration and intrinsically flat band structure. Recently, topological and superconducting states have also been observed in kagome systems. The kagome lattice may also host a "breathing" mode that leads to charge density wave (CDW) states, if there is strong electron-phonon coupling, electron-electron interaction, or external excitation of the material. This "breathing" mode can give rise to candidate distortions such as the star of David (SoD) or its inverse structure [trihexagonal (TrH)]. To date, in most materials, only a single type of distortion has been observed. Here, we present angle-resolved photoemission spectroscopy measurements on the kagome superconductor CsV3Sb5 at multiple temperatures and photon energies to reveal the nature of the CDW in this material. It is shown that CsV3Sb5 displays two intertwined CDW orders corresponding to the SoD and TrH distortions. These two distinct types of distortions are stacked along the c direction to form a three-dimensional CDW order where the two 2-fold CDWs are phase shifted along the c axis. The presented results provide not only key insights into the nature of the unconventional CDW order in CsV3Sb5, but also an important reference for further studies on the relationship between the CDW and superconducting order.
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| 4. |
- Shi, Xun, et al.
(författare)
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Ultrafast electron calorimetry uncovers a new long-lived metastable state in 1T-TaSe2 mediated by mode-selective electron-phonon coupling
- 2019
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Ingår i: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 5:3
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Tidskriftsartikel (refereegranskat)abstract
- Quantum materials represent one of the most promising frontiers in the quest for faster, lightweight, energy-efficient technologies. However, their inherent complexity and rich phase landscape make them challenging to understand or manipulate. Here, we present a new ultrafast electron calorimetry technique that can systematically uncover new phases of quantum matter. Using time- and angle-resolved photoemission spectroscopy, we measure the dynamic electron temperature, band structure, and heat capacity. This approach allows us to uncover a new long-lived metastable state in the charge density wave material 1T-TaSe2, which is distinct from all the known equilibrium phases: It is characterized by a substantially reduced effective total heat capacity that is only 30% of the normal value, because of selective electron-phonon coupling to a subset of phonon modes. As a result, less energy is required to melt the charge order and transform the state of the material than under thermal equilibrium conditions.
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| 5. |
- Wu, Xianxin, et al.
(författare)
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Crossover between electron-electron and electron-phonon mediated pairing on the kagome lattice
- 2024
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Ingår i: Physical Review B. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 109:1
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Tidskriftsartikel (refereegranskat)abstract
- We study electron-electron and electron-phonon mediated pairing in the Holstein extended Hubbard model on the kagome lattice near the van Hove fillings, and we investigate their combined effects on electron pairing states. We find that their combination can promote exotic pairings in a crossover region, where the filling is close to a van Hove singularity. In particular, at the p-type van Hove filling, the E1u (p-wave) and B2u(fy3-3yx2-wave) pairings become leading, and at the m-type van Hove filling, the E1u and A2g (i-wave) pairings get promoted. Moreover, we show that the electron-phonon interaction acquires a significant momentum dependence, due to the sublattice texture of the Fermi surfaces, which can promote non-s-wave pairing. We present a detailed analysis of these pairing propensities, and we discuss implications for the vanadium-based kagome superconductors AV3Sb5.
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