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- He, Hans, et al.
(författare)
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Highly efficient UV detection in a metal-semiconductor-metal detector with epigraphene
- 2022
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Ingår i: Applied Physics Letters. - : American Institute of Physics Inc.. - 0003-6951 .- 1077-3118. ; 120:19
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Tidskriftsartikel (refereegranskat)abstract
- We show that epitaxial graphene on silicon carbide (epigraphene) grown at high temperatures (T >1850 °C) readily acts as material for implementing solar-blind ultraviolet (UV) detectors with outstanding performance. We present centimeter-sized epigraphene metal-semiconductor-metal (MSM) detectors with a peak external quantum efficiency of η ∼85% for wavelengths λ = 250-280 nm, corresponding to nearly 100% internal quantum efficiency when accounting for reflection losses. Zero bias operation is possible in asymmetric devices, with the responsivity to UV remaining as high as R = 134 mA/W, making this a self-powered detector. The low dark currents Io ∼50 fA translate into an estimated record high specific detectivity D = 3.5 × 1015 Jones. The performance that we demonstrate, together with material reproducibility, renders epigraphene technologically attractive to implement high-performance planar MSM devices with a low processing effort, including multi-pixel UV sensor arrays, suitable for a number of practical applications. © 2022 Author(s).
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| 2. |
- Black-Schaffer, Annica M., et al.
(författare)
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Model Evidence of a Superconducting State with a Full Energy Gap in Small Cuprate Islands
- 2013
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Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 110:19, s. 197001-
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Tidskriftsartikel (refereegranskat)abstract
- We investigate subdominant order parameters stabilizing at low temperatures in nanoscale high-Tc cuprate islands, motivated by the recent observation of a fully gapped state in nanosized YBa2Cu3O7-δ[D. Gustafsson et al., Nature Nanotech. 8, 25 (2013)]. Using complementary quasiclassical and tight-binding Bogoliubov–de Gennes methods, we show on distinctly different properties dependent on the symmetry being dx2-y2 þ is or dx2-y2 þ idxy. We find that a surface-induced dx2-y2 þ is phase creates a global spectroscopic gap which increases with an applied magnetic field, consistent with experimental observation.
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| 3. |
- de Graaf, Sebastian Erik, 1986, et al.
(författare)
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Charge Qubit Coupled to an Intense Microwave Electromagnetic Field in a Superconducting Nb Device: Evidence for Photon-Assisted Quasiparticle Tunneling
- 2013
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Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 111:13, s. Art. no. 137002-
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Tidskriftsartikel (refereegranskat)abstract
- We study a superconducting charge qubit coupled to an intensive electromagnetic field and probe changes in the resonance frequency of the formed dressed states. At large driving strengths, exceeding the qubit energy-level splitting, this reveals the well known Landau-Zener-Stückelberg interference structure of a longitudinally driven two-level system. For even stronger drives, we observe a significant change in the Landau-Zener-Stückelberg pattern and contrast. We attribute this to photon-assisted quasiparticle tunneling in the qubit. This results in the recovery of the qubit parity, eliminating effects of quasiparticle poisoning, and leads to an enhanced interferometric response. The interference pattern becomes robust to quasiparticle poisoning and has a good potential for accurate charge sensing.
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| 4. |
- Gustafsson, David, 1982, et al.
(författare)
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Fully gapped superconductivity in a nanometresize YBa2Cu3O7-delta island enhanced by a magnetic field
- 2013
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Ingår i: Nature Nanotechnology. - : Springer Science and Business Media LLC. - 1748-3387 .- 1748-3395. ; 8:1, s. 25-30
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Tidskriftsartikel (refereegranskat)abstract
- The symmetry of Cooper pairs is central to constructing a superconducting state. The demonstration of a d(x2-y2)-wave order parameter with nodes represented a breakthrough for high critical temperature superconductors (HTSs)(1,2). However, despite this fundamental discovery, the origin of superconductivity remains elusive, raising the question of whether something is missing from the global picture. Deviations from d(x2-y2)-wave symmetry(3,4), such as an imaginary admixture d(x2-y2) + is (or id(xy)), predict a ground state with unconventional properties exhibiting a full superconducting gap and time reversal symmetry breaking(5). The existence of such a state, until now highly controversial(6-10), can be proved by highly sensitive measurements of the excitation spectrum. Here, we present a spectroscopic technique based on an HTS nanoscale device that allows an unprecedented energy resolution thanks to Coulomb blockade effects, a regime practically inaccessible in these materials previously. We find that the energy required to add an extra electron depends on the parity (odd/even) of the excess electrons on the island and increases with magnetic field. This is inconsistent with a pure d(x2-y2)-wave symmetry and demonstrates a complex order parameter component that needs to be incorporated into any theoretical model of HTS.
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