| 1. |
- Eremeev, S. V., et al.
(författare)
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Insight into the electronic structure of the centrosymmetric skyrmion magnet GdRu 2 Si 2
- 2023
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Ingår i: Nanoscale Advances. - 2516-0230. ; 5:23, s. 6678-6687
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Tidskriftsartikel (refereegranskat)abstract
- The discovery of a square magnetic-skyrmion lattice in GdRu2Si2, with the smallest so far found skyrmion size and without a geometrically frustrated lattice, has attracted significant attention. In this work, we present a comprehensive study of surface and bulk electronic structures of GdRu2Si2 by utilizing momentum-resolved photoemission (ARPES) measurements and first-principles calculations. We show how the electronic structure evolves during the antiferromagnetic transition when a peculiar helical order of 4f magnetic moments within the Gd layers sets in. A nice agreement of the ARPES-derived electronic structure with the calculated one has allowed us to characterize the features of the Fermi surface (FS), unveil the nested region along kz at the corner of the 3D FS, and reveal their orbital compositions. Our findings suggest that the Ruderman-Kittel-Kasuya-Yosida interaction plays a decisive role in stabilizing the spiral-like order of Gd 4f moments responsible for the skyrmion physics in GdRu2Si2. Our results provide a deeper understanding of electronic and magnetic properties of this material, which is crucial for predicting and developing novel skyrmion-based systems.
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| 2. |
- Mende, Max, et al.
(författare)
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Strong Rashba Effect and Different f−d Hybridization Phenomena at the Surface of the Heavy-Fermion Superconductor CeIrIn 5
- 2022
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Ingår i: Advanced Electronic Materials. - : Wiley. - 2199-160X .- 2199-160X. ; 8:3
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Tidskriftsartikel (refereegranskat)abstract
- New temperature scales and remarkable differences from bulk properties have increasingly placed the surfaces of strongly correlated f materials into the focus of research activities. Applying first-principles calculations and angle-resolved photoelectron spectroscopy measurements, a strong Rashba effect and spin-split surface states at the CeIn surface of the heavy-fermion superconductor CeIrIn5 are revealed. The unveiled 4f-derived electron landscape is remarkably distinct for surface and bulk Ce implying the existence of novel temperature scales near the surface region in this material. These results show that ab initio calculations can reliably predict the unusual electronic and spin structure of surfaces of strongly correlated 4f systems where Rashba spin-orbit-coupling phenomena emerge. It is suggested that the structural blocks of such materials can be combined with magnetically active layers for engineering of novel nanostructural objects with appropriate substrates where the diversity of f-driven properties can be applied for the development of novel functionalities.
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| 3. |
- Mende, Max, et al.
(författare)
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Strong Rashba Effect and Different f−d Hybridization Phenomena at the Surface of the Heavy-Fermion Superconductor CeIrIn5
- 2022
-
Ingår i: Advanced Electronic Materials. - : Wiley. - 2199-160X. ; 8:3
-
Tidskriftsartikel (refereegranskat)abstract
- New temperature scales and remarkable differences from bulk properties have increasingly placed the surfaces of strongly correlated f materials into the focus of research activities. Applying first-principles calculations and angle-resolved photoelectron spectroscopy measurements, a strong Rashba effect and spin-split surface states at the CeIn surface of the heavy-fermion superconductor CeIrIn5 are revealed. The unveiled 4f-derived electron landscape is remarkably distinct for surface and bulk Ce implying the existence of novel temperature scales near the surface region in this material. These results show that ab initio calculations can reliably predict the unusual electronic and spin structure of surfaces of strongly correlated 4f systems where Rashba spin-orbit-coupling phenomena emerge. It is suggested that the structural blocks of such materials can be combined with magnetically active layers for engineering of novel nanostructural objects with appropriate substrates where the diversity of f-driven properties can be applied for the development of novel functionalities.
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| 4. |
- Begunovich, Lyudmila, V, et al.
(författare)
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Triple VTe2/graphene/VTe2 heterostructures as perspective magnetic tunnel junctions
- 2020
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Ingår i: Applied Surface Science. - : ELSEVIER. - 0169-4332 .- 1873-5584. ; 510
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Tidskriftsartikel (refereegranskat)abstract
- New perspective 1.4 nm thick spin-polarized triple heterostructures based on graphene sandwiched between two vanadium ditelluride monolayers (VTe2/graphene/VTe2) were studied using ab initio DFT technique. Both possible trigonal prismatic (H-VTe2) and octahedral (T-VTe2) VTe2 phases were considered to design and study graphene-based heterostructures. It was shown that the interaction with graphene changes the electronic structure of 2D T-VTe2 from metallic to half-metallic, making T phase perspective to be used for magnetic tunnel junctions. The electronic subsystem of graphene fragment is slightly hole doped. Calculated tunnel magne-toresistance ratio for the favorable heterostructure configuration estimated within the Julliere model is 220%, which opens a way to use VTe2/graphene/VTe2 as prospective magnetic tunnel junction in novel spintronic nanodevices based on tunnel magnetic resistance and spin transfer torque effects.
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| 5. |
- Gunbina, A. A., et al.
(författare)
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A 90 GHz SINIS detector with 2 GHz readout
- 2021
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Ingår i: IEEE Transactions on Applied Superconductivity. - 1558-2515 .- 1051-8223. ; 31:5
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Tidskriftsartikel (refereegranskat)abstract
- A superconductor-insulator-normal metal-insulator-superconductor (SINIS) detector integrated in a planar 90 GHz band twin-slot antenna with a 2 GHz superconducting resonator readout was fabricated and experimentally studied. In order to achieve high pixel count, the traditional dc readout of the SINIS detector is replaced by NbN coplanar 13.850 mm long superconducting resonator. SINIS detectors have traditionally dc Junction Field Effect Transistor (JFET) room-temperature readout. Such readout requires individual wiring for each pixel, while the microwave readout is far less cluttered as only one coaxial line is needed for hundreds of devices. Such readout operates similar to frequency domain multiplexing (FDM) for microwave kinetic inductance detectors (MKID). The planar twin slot antenna has two parallel slots in a metal ground plane which are excited coherently by short sections of a coplanar waveguide (CPW) line with a SINIS detector at the center. One section of the CPW is extended past the slot in a long superconducting section which functions as a quarter wavelength resonator. This resonator is short circuited to the ground plane at the far end, with the expected open circuited end terminated by the SINIS detector in the antenna. We measured the response of sample to black body radiation temperatures 6 K and 9 K. The corresponding dynamic resistance maximum drops from 50 k down to 30 k. An RF readout channel comprising a coplanar coupler and a coplanar resonator has a resonant frequency of 1.8 GHz. Unloaded Q factor (without incoming irradiation) is 200. The signal spectral characteristics and the response to the black body radiation have shown design values as expected.
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| 6. |
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| 7. |
- Tarasov, Artem V., et al.
(författare)
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Crystal electric field and properties of 4f magnetic moments at the surface of the rare-earth compound TbRh2Si2
- 2022
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Ingår i: Physical Review B. - 2469-9950. ; 106:15
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Tidskriftsartikel (refereegranskat)abstract
- The crystal electric field (CEF) plays an essential role in defining the magnetic properties of 4f materials. It forces the charge density of 4f electrons and the related magnetic moment to be oriented along a certain direction in the crystal. The CEF and related magnetic properties were widely studied in the past with focus on bulk of 4f materials, while their surfaces have not received much attention. By the example of the antiferromagnetic material TbRh2Si2 and using first-principles calculations and classical 4f angle-resolved photoemission (PE) measurements, we show how the CEF and related magnetic properties, linked with the orientation of 4f moments, are modified at the surface region. Precisely, we studied the CEF characteristics in individual Tb layers for Tb- and Si-terminated surfaces of TbRh2Si2. We show how strongly the CEF changes near the surface and how dramatically it influences the orientation of the 4f moments relative to the bulk. The instructive message of our study is that a rather valuable information about the CEF-related phenomena can be derived from the temperature dependence of 4f PE spectra. The presented methodology including the theoretical approach can be further applied to many other layered and quasi-2D rare-earth-based materials for unveiling their surface magnetic properties.
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| 8. |
- Tarasov, Artem V., et al.
(författare)
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Structural instability at the In-terminated surface of the heavy-fermion superconductor CeIrIn5
- 2022
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Ingår i: Surfaces and Interfaces. - : Elsevier BV. - 2468-0230. ; 32
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Tidskriftsartikel (refereegranskat)abstract
- Driven by reconstruction and relaxation, by the appearance of surface electron states and resonances, the surface properties and related temperature scales of strongly correlated f-materials may differ dramatically from those in the bulk. Applying low energy electron and photoelectron diffraction techniques, momentum-resolved photoelectron spectroscopy and ab initio calculations, we demonstrate that the In-terminated surface of the heavyfermion superconductor CeIrIn5 experiences a reconstruction with a (root 2v x root 2)R45 degrees ordered structure. The latter appears due to the displacement of In atoms with respect to the Ir sublattice. We show that the electronic structure and related properties of the reconstructed In surface differ remarkably from the unreconstructed case. Namely, the predicted surface states with Rashba-type spin splitting do not appear. Our results suggest surface instabilities in similar quasi-two-dimensional strongly correlated f-materials, for which surface reconstructions can be unveiled by means of diffraction techniques.
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| 9. |
- Tarasov, Mikhail, 1954, et al.
(författare)
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Cryogenic Mimim and Simis Microwave Detectors
- 2020
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Ingår i: Proceedings - 2020 7th All-Russian Microwave Conference, RMC 2020. ; , s. 25-27
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Konferensbidrag (refereegranskat)abstract
- Microwave detectors of the Metal-Insulator-Metal-Insulator-Metal (MIMIM) structure and the Superconductor-Insulator-Metal-Insulator-Superconductor (SIMIS) structure have been designed, fabricated and investigated. The difference of such samples was in external electrodes, MIMIM uses copper external electrodes, while SIMIS uses aluminum. Identical in dimensions MIMIM and SIMIS samples have been fabricated and experimentally studied in the temperature range of 0.1-2.7 K. Voltage and current response were measured at 300 GHz external irradiation using Backward Wave Oscillator (BWO). According to our estimates, the MIMIM current responsivity is 1.1·103 A/W in the case of a photon response and 4·104 A/W in the case of a bolometric response. The estimated noise equivalent power is in the range 2.5·10 18 W/v Hz to 1.2·10-19 W/vHz.
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| 10. |
- Tarasov, Mikhail, 1954, et al.
(författare)
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Development of Josephson Traveling-Wave Parametric Amplifier Based on Aluminum SIS Junctions
- 2021
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Ingår i: Physics of the Solid State. - 1063-7834 .- 1090-6460. ; 63:10, s. 1564-1568
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Tidskriftsartikel (refereegranskat)abstract
- Prototypes of the design of Josephson traveling-wave parametric amplifier based on aluminum superconductor–insulator–superconductor junctions in the form of direct-current SQUIDs included in central conductor of coplanar line are developed, fabricated, and investigated. Three manufacturing methods for the fabrication of such devices are tested: two of them using shadow evaporation and one using magnetron sputtering and direct electron-beam lithography. Current–voltage characteristics of the junctions are measured at 0.3 K. A cryogenic setup for the measurement of spectral characteristics of such amplifier containing cold semiconductor amplifier with circulator and cooled attenuators of the channels of input signal and pump is developed. The absorption spectrum of coplanar directional coupler with a quarter-wave resonator dedicated for measurements of short chains from one to 27 SQUIDs is measured.
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