| 1. |
- Bhardwaj, Vishal, et al.
(författare)
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Observation of surface dominated topological transport in strained semimetallic ErPdBi thin films
- 2020
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 117:13
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Tidskriftsartikel (refereegranskat)abstract
- In this Letter, we present experimental observation of surface-dominated transport properties in [110]-oriented strained (∼1.6%) ErPdBi thin films. The resistivity data show typical semi-metallic behavior in the temperature range of 3 K ≤ T ≤ 350 K with a transition from semiconductor- to metal-like behavior below 3 K. The metallic behavior at low temperature disappears entirely in the presence of an external magnetic field >1 T. The weak-antilocalization (WAL) effect is observed in magneto-conductance data in the low magnetic field region and follows the Hikami-Larkin-Nagaoka (HLN) model. HLN fitting estimated single coherent channel, i.e., α ∼-0.51 at 1.9 K, and the phase coherence length (Lφ) shows the Lφ ∼T-0.52 power law dependence on temperature in the range of 1.9 K-10 K, indicating the observation of 2D WAL. Shubnikov-de Haas (SdH) oscillations are observed in magneto-resistance data below 10 K and are fitted to standard Lifhsitz Kosevich theory. Fitting reveals the effective mass of charge carriers ∼0.15 me and a finite Berry phase of 0.86π± 0.16. The sheet carrier concentration and mobility of carriers estimated using SdH data are ns ∼1.35 × 1012 cm-2 and μs = 1210 cm2 V-1 s-1, respectively, and match well with the data measured using the Hall measurement at 1.9 K to be n ∼1.22 × 1012 cm-2, μ = 1035 cm2 V-1 s-1. These findings indicate the non-trivial nature and surface-dominated transport properties of strained (110) ErPdBi thin films at low temperatures.
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| 2. |
- Irfan, Bushra, et al.
(författare)
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Surface dominated magnetotransport in Bi 2 Te 2.15 Se 0.85 topological insulator
- 2018
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 124:21
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Tidskriftsartikel (refereegranskat)abstract
- Topological insulators (TIs) represent a new state of matter possessing an attractive surface spin texture with possible applications in quantum computation and spintronics. The growth of prototypical TIs such as Bi 2Te 3 and Bi 2Se 3 still remains a major challenge, because of vacancies and defects leading to an unintentional doping of the crystals creating a parallel conduction channel in the bulk. Here, we synthesized the Bi 2Te 2.15Se 0.85 (BTS) TI using a modified Bridgeman technique. Magnetotransport studies at different angles and temperatures of the device made on thin (BTS) flakes reveal the 2D nature of the weak antilocalization signal and surface dominated transport properties at low temperatures.
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| 3. |
- Pal, Souvik, et al.
(författare)
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A miniaturized nanobiosensor for choline analysis
- 2014
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Ingår i: Biosensors & bioelectronics. - : Elsevier. - 0956-5663 .- 1873-4235. ; 54, s. 558-564
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Tidskriftsartikel (refereegranskat)abstract
- A novel reusable chemiluminescence choline nanobiosensor has been developed using aligned zinc oxide nanorod-films (ZnONR). The chemically fashioned ZnONR were synthesized by hybrid wet chemical route onto glass substrates and used to fabricate a stable chemiluminescent choline biosensor. The biosensor was constructed by co-immobilization of the enzymes choline oxidase and peroxidase. The covalent immobilization of the enzymes on the ZnONR was achieved using 16-phosphonohexadecanoic acid as a cross-linker. The phosphonation of the ZnONR imparted significant stability to the immobilized enzyme as against physisorbed enzyme. A lower value of Michaelis-Menten constant (K-m), of 0.062 mM for the covalently coupled enzyme over the physisorbed enzymes facilitated enhanced stability of ZnONR nanobiosensor. The ZnONR-choline biosensor has been investigated over a wide range of choline from 0.0005 mM to 2 mM. Importantly, the recovery of choline in milk samples was close to 99%. Using the developed biosensor, choline was measurable even after 30 days with 60 repeated measurements proving the stability of the sensor (Intraday RSD%=2.83 and Interday RSD%=3.51).
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| 4. |
- Srivastava, Shivangi, et al.
(författare)
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Enhanced superconductivity originating from f -electron doping in topologically nontrivial YPdBi half-Heusler thin films
- 2024
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Ingår i: Physical Review Materials. - 2475-9953. ; 8:7
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Tidskriftsartikel (refereegranskat)abstract
- YPdBi is a well-studied diamagnetic topologically trivial half-Heusler alloy that is superconducting with Tc∼1 K. When strained or in thin-film form, it shows a topologically nontrivial surface state with Tc ∼1.25K. ErPdBi is a well-studied topologically nontrivial half Heusler with Tc ∼1.22K. In this work, we demonstrate that the f-electron doping in YPdBi provides a unique way to selectively tune the electronic structure and aid in increasing the superconducting transition temperature of YPdBi. This work presents systematic measurements of electrical resistivity and magnetotransport on half-Heusler thin films of Y(1-x)ErxPdBi (x=0.2, 0.5, and 0.8), prepared using the pulsed laser deposition technique. All the films were observed to be semimetallic, with a sharp downturn in resistivity at low temperatures T < 5 K; the E5 film (Tc∼4.4 K) and E8 film (Tc∼3.7 K) reach a zero-resistivity value, within the experimental limit. The doping of f electron on Y+3 sites possibly gives rise to the improved Fermi parameters and an increase in Tc. Magnetoresistance measurements and first-principle calculations support that Y(1-x)ErxPdBi are topologically nontrivial semimetals. The first-principle calculations also show that with an increase in the doping concentration (x), more f bands start to appear near Fermi level (EF), giving rise to an increase in the band-inversion strength due to s-f exchange interaction. The nontrivial band structure, odd-parity Cooper pair, and noncentrosymmetric crystal structure suggest the presence of unconventional superconductivity in the E5 and E8 films.
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