arXiv subjects

Anuvab Nandi

Publications and source records attributed to Anuvab Nandi.

6 recordsLinked to original sources

arXiv2024

Optimizing defect states in $(Bi_{0.3}Sb_{0.7})_{2}Te_{3}$ ternary topological insulators using indium doping

This study investigates the influence of indium doping on the defect states in (Bi0.3Sb0.7)2Te3 (BST) ternary topological insulators. Thin (10 nm) and thick (60 nm) films of pristine BST and indium-doped BST (In0.14(Bi0.3Sb0.7)1.86Te3) were synthesized using pulsed laser deposition. The electronic properties were characterized through low-frequency noise spectroscopy and temperature-dependent resistance (R-T) measurements. For the 10 nm films, R-T analysis revealed that indium doping shifts the thermal activation energy by approximately 100 meV. This doping also suppresses a shallow impurity band at 72 meV, a finding corroborated by 1/f noise measurements. In the 60 nm films, noise spectroscopy was used to probe deep defect states, where indium doping was found to increase the activation energy from 292.3 meV to 392 meV -- a consistent shift of 100 meV. These findings demonstrate that indium doping is an effective method for systematically modifying both shallow and deep defect states, enhancing the insulating properties and offering a mechanism to engineer the electronic behavior of topological insulators for advanced electronic applications where noise reduction is crucial.

cond-mat.mtrl-sci↗

arXiv2024

Optimizing Oscilloscope based Acquisition for Pulsed Optically Detected Magnetic Resonance Measurements

Ensembles of nitrogen vacancy (NV) defect centers in diamond have emerged as a promising platform for fundamental studies and applications in quantum sensing and quantum information processing. Here, we demonstrate the use of a digital oscilloscope for acquiring pulsed optically detected magnetic resonance (ODMR) data from an ensemble of NV centers in diamond. The oscilloscope facilitates improved signal visualization, and simplifies system debugging. We show that on-board waveform averaging in the oscilloscope enables more efficient measurements. The detection scheme, and data processing are optimized to allow fast acquisition of high quality data. The system noise, and its impact on the measurements is analyzed in detail. The data processing method is shown to effectively suppress a broad range of noise spectral components, thereby reducing the total noise in the processed data. Furthermore, the introduction of an analog low pass filter in the signal path is shown to improve the measurement by removing aliasing. The framework developed in this work can be extended to other detection techniques and material platforms for ODMR. We expect that the insights developed here will guide the design, and development of dedicated instruments for ODMR in future.

quant-ph↗

arXiv2023

Enhancement of spin to charge conversion efficiency at the topological surface state by inserting normal metal spacer layer in the topological insulator based heterostructure

We report efficient spin to charge conversion (SCC) in the topological insulator (TI) based heterostructure ($BiSbTe_{1.5}Se_{1.5}/Cu/Ni_{80}Fe_{20}$) by using spin-pumping technique where $BiSbTe_{1.5}Se_{1.5}$ is the TI and $Ni_{80}Fe_{20}$ is the ferromagnetic layer. The SCC, characterized by inverse Edelstein effect length ($\lambda_{IEE}$) in the TI material gets altered with an intervening Copper (Cu) layer and it depends on the interlayer thickness. The introduction of Cu layer at the interface of TI and ferromagnetic metal (FM) provides a new degree of freedom for tuning the SCC efficiency of the topological surface states. The significant enhancement of the measured spin-pumping voltage and the linewidth of ferromagnetic resonance (FMR) absorption spectra due to the insertion of Cu layer at the interface indicates a reduction in spin memory loss at the interface that resulted from the presence of exchange coupling between the surface states of TI and the local moments of ferromagnetic metal. The temperature dependence (from 8K to 300K) of the evaluated $\lambda_{IEE}$ data for all the trilayer systems, TI/Cu/FM with different Cu thickness confirms the effect of exchange coupling between the TI and FM layer on the spin to charge conversion efficiency of the topological surface state.

cond-mat.mes-hall↗

arXiv2021

Microstrip Line Based Complementary Resonant Structure For Dielectric Characterization

In this work, a complementary resonant structure etched on the ground plane of a microstrip line is proposed for characterizing dielectric materials. The resonant sensor is designed to operate in S-band (2 to 4 GHz). The sensor is designed in an electromagnetic simulator to generate its transmission response, electric and magnetic field maps. A numerical model of the sensor is established to extract the electric permittivity of dielectric samples. The sensor is fabricated on a soft microwave laminate using a rapid photolithography technique. The electric permittivity values of wood, Teflon, and RT/duroid 5880LZ are determined by using the sensor. The permittivity values are found consistent with those available in the literature.

physics.app-ph↗

arXiv2021

Detection of electron spin resonance down to 10 K using localized spoof surface plasmon

In this study, novel use of the electromagnetic field profile of a localized spoof surface plasmonic mode to detect electron spin resonance is being reported. The mode is supported on a resonator with a complementary metallic spiral structure, etched on the ground plane of a microstrip line having a characteristic impedance of 50 $Ω$. The change in characteristics of the mode of interest with lowering of temperature has been observed and analyzed. Electron spin resonance spectra of a standard paramagnetic sample, 2,2-diphenyl-1-picrylhydrazyl, are recorded using this resonator down to 10 K. Potential application of the mode in the detection of microwave Rashba field-driven electron spin resonance has been discussed.

physics.app-ph↗

arXiv2020

S-band electron spin resonance spectroscopy using a short-circuited coplanar waveguide resonator

In this work, we study the development of a coplanar waveguide (CPW) resonator and its use in an electron spin resonance (ESR) spectrometer. The CPW resonator is designed to operate in S-band. It has a short circuit configuration which leads to miniaturization. It is so constructed such that it has a characteristic impedance of 50 ohms. Detailed electromagnetic simulation with a particular emphasis on the excitation of the structure has been performed for this resonator owing to its uniplanar nature. The design parameters and the electromagnetic field distribution are obtained from the simulation. The resonator is fabricated using optical lithography with a rapid prototyping technique. The characteristic response of the resonator is measured by coupling it to a Vector Network Analyzer (VNA). The ESR absorption spectrum of free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) is captured by using this resonator in reflection geometry. The microwave magnetic field distribution at the sample position is investigated.The measured g-factor value is found to be consistent with that reported in the literature. The quality factor of this resonator is found to be low and this makes it suitable for use in a Pulsed ESR spectrometer.

physics.app-ph↗