| 1. |
- Slager, Robert-Jan, et al.
(författare)
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Self-organized pseudo-graphene on grain boundaries in topological band insulators
- 2016
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Ingår i: PHYSICAL REVIEW B. - 2469-9950. ; 93:24
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Tidskriftsartikel (refereegranskat)abstract
- Semimetals are characterized by nodal band structures that give rise to exotic electronic properties. The stability of Dirac semimetals, such as graphene in two spatial dimensions, requires the presence of lattice symmetries, while akin to the surface states of topological band insulators, Weyl semimetals in three spatial dimensions are protected by band topology. Here we show that in the bulk of topological band insulators, self-organized topologically protected semimetals can emerge along a grain boundary, a ubiquitous extended lattice defect in any crystalline material. In addition to experimentally accessible electronic transport measurements, these states exhibit a valley anomaly in two dimensions influencing edge spin transport, whereas in three dimensions they appear as graphenelike states that may exhibit an odd-integer quantum Hall effect. The general mechanism underlying these semimetals-the hybridization of spinon modes bound to the grain boundary-suggests that topological semimetals can emerge in any topological material where lattice dislocations bind localized topological modes.
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| 2. |
- Lu, Haiyu, et al.
(författare)
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Identification of a characteristic doping for charge order phenomena in Bi-2212 cuprates via RIXS
- 2022
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Ingår i: Physical Review B. - 2469-9969 .- 2469-9950. ; 106:15
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Tidskriftsartikel (refereegranskat)abstract
- Identifying quantum critical points (QCPs) and their associated fluctuations may hold the key to unraveling the unusual electronic phenomena observed in cuprate superconductors. Recently, signatures of quantum fluctuations associated with charge order (CO) have been inferred from the anomalous enhancement of CO excitations that accompany the reduction of the CO order parameter in the superconducting state. To gain more insight into the interplay between CO and superconductivity, here we investigate the doping dependence of this phenomenon throughout the Bi-2212 cuprate phase diagram using resonant inelastic x-ray scattering (RIXS) at the Cu L3 edge. As doping increases, the CO wave vector decreases, saturating near a commensurate value of 0.25 reciprocal lattice unit beyond a characteristic doping pc, where the correlation length becomes shorter than the apparent periodicity (4a0). Such behavior is indicative of the fluctuating nature of the CO; the proliferation of CO excitations in the superconducting state also appears strongest at pc, consistent with expected behavior at a CO QCP. Intriguingly, pc appears to be near optimal doping, where the superconducting transition temperature Tc is maximal.
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