Abstract Unconventional superconductors have Cooper pairs with lower symmetries than in conventional superconductors. In most unconventional superconductors, the additional symmetry breaking occurs in relation to typical ingredients such as strongly correlated Fermi liquid phases, magnetic fluctuations, or strong spin-orbit coupling in noncentrosymmetric structures. In this article, we show that the time-reversal symmetry breaking in the superconductor LaNiGa 2 is enabled by its previously unknown topological electronic band structure, with Dirac lines and a Dirac loop at the Fermi level. Two symmetry related Dirac points even remain degenerate under spin-orbit coupling. These unique topological features enable an unconventional superconducting gap in which time-reversal symmetry can be broken in the absence of other typical ingredients. Our findings provide a route to identify a new type of unconventional superconductors based on nonsymmorphic symmetries and will enable future discoveries of topological crystalline superconductors.
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Van Der Waals Heterostructures with Spin‐Orbit Coupling
Herein, recent work on van der Waals (vdW) systems in which at least one of the components has strong spin‐orbit coupling is reviewed, focussing on a selection of vdW heterostructures to exemplify the type of interesting electronic properties that can arise in these systems. First a general effective model to describe the low energy electronic degrees of freedom in these systems is presented. The model is then applied to study the case of (vdW) systems formed by a graphene sheet and a topological insulator. The electronic transport properties of such systems are discussed and it is shown how they exhibit much stronger spin‐dependent transport effects than isolated topological insulators. Then, vdW systems are considered in which the layer with strong spin‐orbit coupling is a monolayer transition metal dichalcogenide (TMD) and graphene‐TMD systems are briefly discussed. In the second part of the article, a case is discussed in which the vdW system includes a superconducting layer in addition to the layer with strong spin‐orbit coupling. It is shown in detail how these systems can be designed to realize odd‐frequency superconducting pair correlations. Finally, twisted graphene‐NbSe2 bilayer systems are discussed as an example in which the strength of the proximity‐induced superconducting pairing in the normal layer, and its Ising character, can be tuned via the relative twist angle between the two layers forming the heterostructure.
more » « less- NSF-PAR ID:
- 10454751
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Annalen der Physik
- Volume:
- 532
- Issue:
- 2
- ISSN:
- 0003-3804
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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T N= 132 ± 1 K, CrSBr adopts an A‐type antiferromagnetic structure with each individual layer ferromagnetically ordered internally and the layers coupled antiferromagnetically along the stacking direction. Scanning tunneling spectroscopy and photoluminescence (PL) reveal that the electronic gap is ΔE= 1.5 ± 0.2 eV with a corresponding PL peak centered at 1.25 ± 0.07 eV. Using magnetotransport measurements, strong coupling between magnetic order and transport properties in CrSBr is demonstrated, leading to a large negative magnetoresistance response that is unique among vdW materials. These findings establish CrSBr as a promising material platform for increasing the applicability of vdW magnets to the field of spin‐based electronics. -
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Abstract Two‐dimensional transition metal dichalcogenides (TMDs)/graphene van der Waals (vdW) heterostructures integrate the superior light–solid interaction in TMDs and charge mobility in graphene, and therefore are promising for surface‐enhanced Raman spectroscopy (SERS). Herein, a novel TMD (MoS2and WS2) nanodome/graphene vdW heterostructure SERS substrate, on which an extraordinary SERS sensitivity is achieved, is reported. Using fluorescent Rhodamine 6G (R6G) as probe molecules, the SERS sensitivity is in the range of 10−11to 10−12
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