Department of Physics

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IIT Jodhpur

A very high precision interferometric sensor with a resolution up to ~λ/1940 is reported, exploiting Talbot effect, revivals of the initial phase, oscillation in transverse momentum, multimode interference inside a hollow photonic bandgap waveguide. © OSA 2020 © 2020 The Author(s)

World University root node

Optics InfoBase Conference Papers

Photonic crystal based ultra-sensitive interferometric nanometer displacement sensor

Theories beyond the standard model often predict the existence of an additional neutral boson, the Z′. Using data collected by the Belle II experiment during 2018 at the SuperKEKB collider, we perform the first searches for the invisible decay of a Z′ in the process e+e-→μ+μ-Z′ and of a lepton-flavor-violating Z′ in e+e-→e±μZ′. We do not find any excess of events and set 90% credibility level upper limits on the cross sections of these processes. We translate the former, in the framework of an Lμ-Lτ theory, into upper limits on the Z′ coupling constant at the level of 5×10-2-1 for MZ′≤6 GeV/c2. © 2020 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the "https://creativecommons.org/licenses/by/4.0/" Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP3.

Physical Review Letters

Search for an Invisibly Decaying Z′ Boson at Belle II in e+e- →μ+μ- (e±μ) Plus Missing Energy Final States

Copper-based ternary CuSb(S/Se)2 compound semiconductors are showing promise for ultrathin photovoltaic devices. The high absorption coefficient of these semiconductors makes them suitable for very thin absorber, where maximum absorption can be achieved in a photovoltaic device with only nanometers thick CuSb(S/Se)2 based thin films. The device structure under consideration consists of AZO/i-ZnO/n-CdS/absorber layer/back contact, as the constituent material layers. The device structure is simulated using one dimensional solar cell capacitance simulator (SCAPS 1D) under one sun illumination and considering flat band approximation for the back contact and CuSb(S/Se)2 interface. The optimized single junction device efficiencies are approximately 14% and approximately 10.18% with CuSbS2 and CuSbSe2 absorbers, respectively. Further, the impact of various material parameters such as thickness, acceptor concentration of bulk absorber layer, donor concentration of CdS buffer layer, and defects present at bulk absorber layer and at the buffer/absorber interface is discussed in correlation with the photovoltaic performance of the considered devices. The bandgap of CuSb(S/Se)2 reduces linearly with Se alloying, and their impact on device performance is quantified in terms of capacitance voltage (CV), capacitance frequency (Cf), and impedance spectra of the photovoltaic device. © 2020 John Wiley & Sons Ltd

International Journal of Energy Research

Simulation studies on photovoltaic response of ultrathin CuSb(S/Se)2 ternary compound semiconductors absorber-based single junction solar cells

We have studied the low-temperature magnetic and infrared data of the BiFeO3 ceramic sample to investigate the behavior of phonons and magnon-phonon coupling below 300 K. From the magnetic study, we noticed two magnetic transitions near 150 and 257 K due to the spin-reorientation. Besides, this sample is found to be a mean-field system rather than a glassy system. In our assignment of the infrared modes, all the 13 allowed phonon modes are accounted for rhombohedral BiFeO3 at room temperature itself. Almost all the modes show anomalous behavior in their frequency dependence, close to the observed magnetic transitions. In addition, the emergence of two-magnon modes at 106 and 111 cm−1 below 160 K is observed due to a modification in the noncollinear spin structure. These results indicate the presence of magnon-phonon coupling in multiferroic BiFeO3 below room temperature. © 2020

Journal of Alloys and Compounds

Emergence of two-magnon modes below spin-reorientation transition and phonon-magnon coupling in bulk BiFeO3: An infrared spectroscopic study

Earlier this year, the Belle collaboration presented their new measurements of RD and RD⁎ using a new method. These measurements are consistent with the Standard Model predictions, whereas the global averages of the earlier measurements had a 4.1σ discrepancy. With the inclusion of the new data in the global averages, the discrepancy comes down to 3.1σ. In this work, we study the new physics solutions to the RD-RD⁎ anomaly allowed by the reduction in the discrepancy. Among the four fermion operators, which arise through a single particle exchange, only the (V−A) operator solution survives. We found three additional solutions with two dis-similar operators. The branching ratio of Bc→τν¯ is powerful discriminant between these four allowed solutions. © 2020 The Authors

Fulltext

Nuclear Physics B

Solutions to RD-RD⁎ in light of Belle 2019 data

In this work, we derive a quantum information theoretic quantity similar to the Leggett-Garg inequality, which can be defined in terms of neutrino transition probabilities. For the case of νμ→νe/ν¯μ→ν¯e transitions, this quantity is sensitive to CP violating effects as well as the neutrino mass-hierarchy, namely which neutrino mass eigenstate is heavier than the other ones. The violation of the inequality for this quantity shows an interesting dependence on mass-hierarchy. For normal (inverted) mass-hierarchy, it is significant for νμ→νe (ν¯μ→ν¯e) transitions. This is applied to the two ongoing accelerator experiments T2K and NOνA as well as the future experiment DUNE. © 2019 The Author(s)

A quantum information theoretic quantity sensitive to the neutrino mass-hierarchy

Various nonclassical and quantum phase properties of photon added then subtracted displaced Fock state have been examined systematically and rigorously. Higher-order moments of the relevant bosonic operators are computed to test the nonclassicality of the state of interest, which reduces to various quantum states (having applications in quantum optics, metrology and information processing) in different limits ranging from the coherent (classical) state to the Fock (most nonclassical) states. The nonclassical features are discussed using Klyshko's, Vogel's, and Agarwal–Tara's criteria as well as the criteria of lower- and higher-order antibunching, sub-Poissonian photon statistics and squeezing. In addition, phase distribution function and quantum phase fluctuation have been studied. These properties are examined for various combinations of number of photon addition and/or subtraction and Fock parameter. The examination has revealed that photon addition generally improves nonclassicality, and this advantage enhances for the large (small) values of displacement parameter using photon subtraction (Fock parameter). The higher-order sub-Poissonian photon statistics is only observed for the odd orders. In general, higher-order nonclassicality criteria are found to detect nonclassicality even in the cases when corresponding lower-order criteria failed to do so. Photon subtraction is observed to induce squeezing, but only large number of photon addition can be used to probe squeezing for large values of displacement parameter. Further, photon subtraction is found to alter the phase properties more than photon addition, while Fock parameter has an opposite effect of the photon addition/subtraction. Finally, nonclassicality and non-Gaussianity is also established using Q function. © 2019 Elsevier B.V.

Optics Communications

Impact of photon addition and subtraction on nonclassical and phase properties of a displaced Fock state

The irradiation effect of high energy silver ion (Ag8+) has been investigated on ZnO thin films to understand their impact on structural, microstructural, optical, electronic and magnetic properties. The RF sputtered pristine ZnO/Si thin films are polycrystalline and highly textured along (0 0 2) plane. The irradiated ZnO/Si samples showed enhanced structural and microstructural defects with irradiation time. The lattice parameters have reduced for irradiated ZnO thin films, suggesting structural deformation. The irradiation has resulted into enhanced defect density and strain in these thin films. A weak room temperature ferromagnetic moment (3.24 × 10−4 emu cm−2) has been observed, which has reduced drastically for Ag8+ irradiated samples up to 1.05 × 10−4 emu cm−2. The observed reduction in saturation magnetization has been attributed to the enhanced microstructural defects, lowering the free charge carriers and increasing the recombination centers simultaneously. © 2020

Vacuum

Ag8+ ion irradiation modulated structural, microstructural, defect, and magnetization in ZnO thin films

BiFeO3 based resistive random access memory (RRAM) devices are fabricated using a low-cost solution process to study the effect of an Al top electrode on switching behavior and reliability. Fabricated devices demonstrated bipolar switching characteristics with a moderate Ion/Ioff ratio, set and reset voltages of ∼-1.3 V and ∼0.8 V, DC and AC endurance of more than 250 cycles and 7100 cycles, respectively, and a retention time of over 104 s, confirming the non-volatile resistive switching behavior. The ohmic and trap filled space charge limited conduction dominates the conduction mechanism in the devices at lower and higher voltages, respectively. Moreover, impedance spectroscopy measurements substantiate the presence of an AlOx layer at the Al/BiFeO3 interface resulting from the Al-O interaction at the junction, which is the possible rationale of reliable complementary switching in these RRAM devices. The switching mechanism is elucidated using the formation and rupture of the oxygen vacancy mediated filament, assisted by the participation of a thin AlOx layer at the Al/BFO interface. The role of the thin AlOx layer is explained by modeling of impedances. © 2020 Author(s).

AIP Advances

Interfacial layer assisted, forming free, and reliable bipolar resistive switching in solution processed BiFeO3 thin films

The quantum channels with memory, known as non-Markovian channels, are of crucial importance for a realistic description of a variety of physical systems, and pave ways for new methods of decoherence control by manipulating the properties of an environment such as its frequency spectrum. In this work, the reduced dynamics of a coin in a discrete-time quantum walk is characterized as a non-Markovian quantum channel. A general formalism is sketched to extract the Kraus operators for a t-step quantum walk. Non-Markovianity, in the sense of P indivisibility of the reduced coin dynamics, is inferred from the nonmonotonous behavior of distinguishability of two orthogonal states subjected to it. Furthermore, we study various quantum information-theoretic quantities of a qubit under the action of this channel, putting in perspective the role such channels can play in various quantum information processing tasks. © 2020 American Physical Society.