Alex Hayat’s research while affiliated with Technion – Israel Institute of Technology and other places

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Publications (98)


High-Temperature Superconductor Based Mid-Infrared Detector
  • Article

April 2025

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6 Reads

Optics Communications

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Shlomi Bouscher

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Alex Hayat

Fabrication process for YBCO nanowire. (a) The figure shows an STO substrate with a (100) orientation. (b) Substrate is spin-coated with LOR and 1505 photoresist, respectively, using a spin-coating technique. (c) Using a laser beam, specific regions of the photoresist are exposed. Only the gray-shaded region of the mask is subjected to exposure. (d) After the development process, the exposed photoresist is removed, leaving behind the desired pattern. (e) A 20 nm thin film of Al2O3 is deposited onto the substrate using an e-gun deposition technique. (f) The Al2O3 film is then lifted off by immersing the sample in an NMP solution. (g) Finally, YBCO is deposited over the entire sample, but crystalline YBCO growth occurs exclusively within the areas where the STO substrate was exposed.
Structure and composition characterization of YBCO film. (a) The XRD pattern of 50 nm YBCO film grown on LaAlO3 substrate using PLD. The planes shown in pink color belong to YBCO and the purple color indicates the LaAlO3 substrate, respectively. (b) EDS maps of Y, Ba, Cu, and O, along with substrate elements, were scanned in the specified region and are shown in the inset of the SEM image. EDS spectrum provides the compositional information for the deposited YBCO film. (c) ToF-SIMS analysis of the YBCO film, showing the variation of the ions present in the film and the substrate down to a depth of ∼100 nm. (d)–(f) 3D map of the Y⁺ (red), Ba⁺ (green), and Cu⁺ (purple) along with the substrate (blue). Data were taken on a spot size of 50  × 50  μ m 2 area.
Figure shows the SEM images and electrical characterization of the 50 nm thin YBCO film. (a) SEM images of 200 nm wide and 5  μm long (inside yellow dashed rectangle) and T c = 84 K, (b) 450 nm wide and 10  μm long (inside yellow dashed rectangle), and the superconducting transition temperature T c = 85 K, and (c) meander structure with 750 nm wide wire and T c = 79 K. All the SEM imaging was conducted after the deposition of YBCO. The superconducting YBCO film and insulating film (on Al2O3 thin film) regions have been mentioned in each SEM image. (d) Resistance as a function of temperature measurement of the 50 nm thin YBCO meander structure with 750 nm width is shown in the figure with a T c = 79 K. (e) Surface plot of the I–V curve at different temperatures. A critical current dome can be distinguished with the dashed line (a guide to the eye). (f) The I–V plot for selected temperatures.
(a) A schematic of the experimental setup for the photoresponse and wavelength-dependent study of the nanowires. L: lens, M: mirror, FM: flip mirror, BS: beam splitter, LPF: low pass filter, C: chopper, and ND: neutral density filter. (b) Measured photoresponse of the 750 nm nanowire vs frequency (green circles) and fitted single-pole transfer function H f = 1 / ( 1 + f / f − 3 d B 2 (blue curve).
Photoresponse vs bias current at different temperatures for (a) 450 nm wide and 10  μ m long wire, (b) 750 nm wide meander structure. Inset shows the d R / d T vs T variation. The color bar represents the ac voltage response (in mV) in each panel. The data presented in the main panels have been subjected to interpolation to improve visualization and smoothness.

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Optical response in a high-Tc YBCO nanowire
  • Article
  • Publisher preview available

July 2024

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50 Reads

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3 Citations

We demonstrate the optical response from high-Tc superconductor nanowires at temperatures above that of liquid nitrogen. Using hard oxide A l 2 O 3 as a mask material, we achieved miniaturized YB a 2 C u 3 O 7 − δ wires with widths nearing 100 nm, a significant milestone for highly sensitive photodetectors. We investigated the photoresponse of these nanowires at temperatures almost an order of magnitude higher than previously reported, under varying temperature and bias current conditions. Our findings reveal a strong correlation between the optical response and the critical parameters of the superconductor, with peak optical responses close to the critical values of temperature and bias current density. Nanowire response to wavelengths from visible to near-infrared range demonstrated a pronounced absorption maximum at temperatures below Tc. These results lay a solid foundation for the development of high-Tc superconductor nanowire single-photon detectors, understanding of nanoscale high-Tc superconductor structure optical behavior, and advancing the prospects of quantum technologies.

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Fig. 2 Superlattice SLED emitting regions and EL spectra. a Schematic drawing of the emitting regions in the superlattice SLED. Longer wavelength emission arises from the n-type GaAs layer adjacent to the superconducting contact while shorter wavelength emission arises from the intrinsic PN junction. The superconducting contact obscures emission from the top layer due to its thickness. b Image of an emitting device. Emission is observed only from the periphery of the device due to the opaqueness of the contact. The diagonal lines are due to the screen's refresh rate. c-f Spectral emission of the device vs. temperature for selected current values. All spectra demonstrate decay below T c . The vertical dashed blue and red lines mark the positions of the two emission features. The top insets in c-f depict the decay of the two emission features (blue -shorter wavelength, red -longer wavelength, corresponding to the vertical dashed lines) with temperature and a fit to the expected dependence of Δ 2 (T). The transparent ribbons represent a confidence margin of ±σ for the theoretical fits. The bottom insets in c-f depict a single recorded spectrum at 6K (black horizontal dashed line), showing the shape of the two features, including the fitting for each feature (blue for shorter wavelength and red for longer wavelength)
Fig. 5 Normalized EL spectra maximum and minimum vs. current and temperature. a Value of the peak of the normalized spectra vs. temperature and applied current, having a superconducting-dome-like signature. The inset depicts the critical current-temperature relation, the solid black line is the calculated dependence, with the transparent red ribbon representing a confidence margin of ±σ. b Value of the dip of the normalized spectra vs. temperature and applied current, having a superconducting-dome-like signature
Fig. 6 Photon coincidence measurements of superlattice SLED emission. g (2) (τ = 0,T), indicating photon-pair correlations below T c . The black curve is a calculated dependence. The transparent red ribbon represents a confidence margin of ±σ for the theoretical model. The inset shows g (2) (τ) vs. temperature. A peak is observed at τ = 0 with a width of ~0.5 ns, matching the total jitter of both APDs
Two-photon emission from a superlattice-based superconducting light-emitting structure

June 2024

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40 Reads

Light Science & Applications

Superconductor-semiconductor hybrid devices can bridge the gap between solid-state-based and photonics-based quantum systems, enabling new hybrid computing schemes, offering increased scalability and robustness. One example for a hybrid device is the superconducting light-emitting diode (SLED). SLEDs have been theoretically shown to emit polarization-entangled photon pairs by utilizing radiative recombination of Cooper pairs. However, the two-photon nature of the emission has not been shown experimentally before. We demonstrate two-photon emission in a GaAs/AlGaAs SLED. Measured electroluminescence spectra reveal unique two-photon superconducting features below the critical temperature ( T c ), while temperature-dependent photon-pair correlation experiments ( g ⁽²⁾ ( τ , T )) demonstrate temperature-dependent time coincidences below T c between photons emitted from the SLED. Our results pave the way for compact and efficient superconducting quantum light sources and open new directions in light-matter interaction studies.



Two-Photon Emission and Correlations in Hybrid Superconductor-Semiconductor Devices

January 2024

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1 Read

We experimentally demonstrated two-photon emission in GaAs/AlGaAs superconducting light emitting diodes (SLEDs), observing EL spectra and g ⁽²⁾ photon correlations corresponding to Cooper-pair recombination. We utilized a superlattice structure and transparent superconducting contacts to enhance pair emission.





Ultrafast low-jitter optical response in high-temperature superconducting microwires

May 2023

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66 Reads

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8 Citations

We report ultrafast optical response in high-Tc superconductor (YBa2Cu3O7−δ) based microwires operating at 76 K and we find a rise time ∼850 ps and a fall time ∼1250 ps and an upper limit of timing jitter of ∼100 ps, using twice the standard deviation of the fitted data. In our experiment, incident power is proven to be an important factor for a device jitter. At low incident power, a lower rate of hot-spot generation by a smaller number of absorbed photons results in a longer latency time to obtain the required number of hot-spots for superconductor-to-normal transition. The lower hot-spot generation rate also results in larger timing jitter of the device. Whereas, at high incident power, a higher hot-spot generation rate yields shorter latency and smaller timing jitter. These observations agree well with our statistical model. Enhancing the sensitivity of the current device can enable future high-Tc superconductor nanowire single photon detectors, toward the widespread use of ultrafast quantum technologies.


Universal photonic quantum gate by Cooper-pair-based optical nonlinearity

April 2023

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12 Reads

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1 Citation

We propose a compact and highly efficient scheme for solid-state photonic quantum gates. At the core of our scheme is a SWAPϕ gate based on giant Cooper-pair-based optical nonlinearity we predict in a semiconductor-superconductor structure, selectively introducing a phase to the |Ψ+〉 Bell state. We theoretically demonstrate this scheme on a practical device based on a superconducting contact coupled to a GaAs/AlGaAs waveguide structure. We model the Cooper-pair-induced nonlinear change of the refractive index showing strong nonlinearities at energies close to the superconducting gap inside a semiconductor band. We calculate the fidelity of the proposed SWAPϕ gate, as well as the sensitivity of the gate to device parameters. As short photon wave packets are crucial for efficient higher-order interactions, we investigate the integrated fidelity for short wave packets with different central wavelengths and bandwidths, providing limiting factors as well as possible optimizations. This theoretically demonstrated concept can pave the way toward practical realizations of scalable photonic quantum circuits.


Citations (45)


... [19] The Lombardi team utilized optimized IBE technology combined with a hard mask to fabricate 65 nm wide nanowires on a 10 nm-thick YBCO film and measured dark pulses at 9.3 K. [14,16] Amari et al. employed ion irradiation technology to prepare 30 nm-thick, 126 nm wide YBCO nanowires, followed by encapsulation for protection. [26] Additionally, some novel nanowire patterning methods have emerged, such as using alumina templates, [27,28] SrTiO 3 insulating film templates, [29,30] AFM contact lithography, [31] and superlattice nanowire pattern transfer (SNAP). [32] For example, Kumar et al. used Al 2 O 3 as a mask to fabricate YBCO nanowires with a width close to 100 nm, achieving an optical response above the liquid nitrogen temperature (81 K), but the film thickness was 50 nm. ...

Reference:

Minimal Damage and Tunable Fabrication of Atomic‐Scale Ultrathin YBa2Cu3O7‐δ Nanowires with High Uniformity
Optical response in a high-Tc YBCO nanowire

... Therefore, the careful choice of the material is crucial. In particular, recent experiments show that HTS exhibits low jitter times and ultra-fast response times on the order of 100 ps, [17][18][19][20] while LTS nanowires typically show three orders higher response times (about 10-40 ns). The general physics of SNSPD is typically modeled by tracking the quasi-particle generation from the photon incidence or, equivalently, by calculating the temperature evolution and its effect on superconducting properties. ...

Ultrafast low-jitter optical response in high-temperature superconducting microwires
  • Citing Article
  • May 2023

... It was shown theoretically 28 that a spin-singlet Cooper pair may recombine with a pair of holes, resulting in a polarization-entangled photon pair in the |Ψ þ 〉 Bell state. This concept has been shown to be also at the core of Cooper-pair based twophoton amplification in waveguides 29 , Bell-state analyzers 30 and nonlinear photonic universal quantum gates 31 . While the nearly deterministic on-demand sources such as single atoms or quantum dots (QD) offer certain advantages [32][33][34] , the most widely used source of entangled photons in quantum information processing (QIP) is parametric down conversion (PDC) 5,[35][36][37][38][39][40][41][42][43] , which has a probabilistic naturevery similar to the SLED source. ...

Universal photonic quantum gate by Cooper-pair-based optical nonlinearity
  • Citing Article
  • April 2023

... Exciton-polaritons [1], half-light half-matter quasiparticles, arise from the strong coupling regime between an excitonic and a photonic state when the coupling rate between the two states is faster than the respective dissipation rates. Exciton-polaritons have been demonstrated in many nanofabricated photonic strutures such as microcavities [1][2][3], photonic crystals waveguides [4][5][6][7][8][9][10][11][12][13][14][15] or micropillar lattices [16][17][18]. From their hybrid nature, the exciton-polaritons hold the properties of their light and matter counterparts, and therefore are nonlinear bosons that can ballistically propagate. ...

Two-photon pumped exciton-polariton condensation

... Quantum tunneling at metallic surfaces is the physical principle behind the operation of the scanning tunneling microscope [11][12][13] . It also lays a foundation for nanotechnologies, such as the tunnel diode 14 and resonant tunneling 15 , and some interdisciplinary sciences including quantum biology [16][17][18] and quantum chemistry 19,20 . As a ubiquitous behavior of microscopic matters, such as electron 21 , proton 22 , nucleon 9 , photon 23,24 , and superconducting Cooper pairs 25 , quantum tunneling has been observed in many experiments 20,[26][27][28][29][30][31] . ...

Enhanced Cooper-Pair Injection into a Semiconductor Structure by Resonant Tunneling
  • Citing Article
  • March 2022

Physical Review Letters

... More complex structures, however, cannot be formulated analytically, hence, we have previously introduced a method for finding strongly coupled structures via a near-field inverse design approach [32]. In accordance with this method, we run an evolutionary optimization based on a genetic algorithm, where the optimization function is defined as the mean intensity E m of the near-field optical response in a small spectral window around λ exc . ...

Optimizing the strong coupling of excitons in 2D materials and surface plasmon lattice resonances
  • Citing Conference Paper
  • January 2020

... Notably, with unconventional pairing states, such as d-wave pairings, the dGSJ states evolve into flat zero-energy surface Andreev bound states (ZESABSs) [13][14][15][16] and can be found at normal regions of arbitrary thickness [17,18]. The ZESABSs manifest themselves as a zero bias conductance peak in tunneling spectroscopy [14,17,[19][20][21][22][23]. ...

High-T c Cooper-pair injection in a semiconductor-superconductor structure

... Recently, Xing et al fabricated a nanostrip with 10 µm width and 100 nm thickness by PLD and selective epitaxial growth method. The J c of the nanostrip was 5.5 ×10 5 A cm −2 at 77 K and showed a photo-response above 85 K [24]. However, it is technologically challenging to fabricate a high quality cuprate nanostrip with a 5 nm thick and 100 nm wide dimensions, and the single-photon sensitivity can not be compared with Nbbased SNSPD [25]. ...

Photoresponse above 85 K of selective epitaxy grown high-T c superconducting microwires
  • Citing Article
  • July 2020

... A similar scenario is also observed in the heterostructures of PbS QDs and plasmonic Cu 2-x Se nanocrystals [64]. Strugo et al. numerically studied the plasmon-assisted Cooper-pair-based two-photon emission in a superconducting Nb layer [317]. With an SPP mode traveling along the interface between the highly doped n-type InGaAs and Nb layers, the superconductorsemiconductor waveguiding system witnesses a 45-fold enhancement in mode confinement and the two-photon gain elevated by 3 orders of magnitude, implying a high potential in two-photon lasing. ...

Enhanced two-photon amplification in superconductor-semiconductor plasmonic waveguides

... [14] Leveraging the impact of the optical Stark effect (OSE) on these exciton-polaritons confined between two DBR mirrors becomes particularly promising, given the successful control of polaritons. [15][16][17] In recent times, researchers have explored the influence of the OSE in 2D WS2 [18] monolayers at room temperature and developed an all-optical method to realize topological insulators using OSE within exciton-polariton systems. [19] These studies provide ways to manipulate polaritons through OSE with a large degree of control freedom. ...

Ultrafast Manipulation of a Strongly Coupled Light–Matter System by a Giant ac Stark Effect
  • Citing Article
  • November 2019

ACS Photonics