Department of Physics

&ldquo;IIT Jodhpur is committed to impart quality education to facilitate the creation of qualified, competent and responsible human resources to meet the emerging technological challenges of the world. It is working towards creating an equitable learning platform that is positive, accessible and effective in the face of the modern societal and scientific advancements.

Flexibility in curriculum, in all its academic programs, encompassing elements of teaching, research, creativity, innovation and entrepreneurship is the most unique feature of IIT Jodhpur. The Department of Science and Technology (DST), under the National Mission on Cyber Physical Systems, has identified IIT Jodhpur as a Technology &amp; Innovation Hub in the area of Augmented Reality and Virtual Reality. The institute has also been nominated as the coordinator for the Jodhpur City and Knowledge Cluster by the Office of Principal Scientific Adviser, Government of India.

The sprawling 852-acre IIT Jodhpur campus is a majestic tribute to the deep-rooted diverse cultural heritage of the region. The campus is an architectural masterpiece, which is slated to become an international exemplar of sustainability with net-zero energy, and advanced water and waste management strategies.&rdquo;

IIT Jodhpur

We report on the electronic energy-level diagram of polycrystalline BiFeO3 using the elemental, optical, and current-density-electric field (J-E) characteristics. The elemental, electronic composition, and valence-band structure of BiFeO3 ceramics were studied using x-ray photoelectron spectroscopy. The diffuse reflectance spectrum of a mixture of BiFeO3 and BaSO4, used as a standard, was recorded to test the Kubelka-Munk model. From the graph of the Kubelka-Munk function versus wavelength, two charge-transfer bands and two doubly degenerated d-d transitions (6A1g → 4T2g and 6A1g → 4T1g) were observed in polycrystalline BiFeO3. The J-E curves measured on the BiFeO 3 ceramics showed space-charge-limited conduction mechanism. © 2010 The American Physical Society.

World University root node

Physical Review B - Condensed Matter and Materials Physics

Charge transfer and electronic transitions in polycrystalline BiFeO 3

We develop a unified, information theoretic interpretation of the number-phase complementarity that is applicable both to finite-dimensional (atomic) and infinite-dimensional (oscillator) systems, with number treated as a discrete Hermitian observable and phase as a continuous positive operator valued measure (POVM). The relevant uncertainty principle is obtained as a lower bound on entropy excess, X, the difference between the entropy of one variable, typically the number, and the knowledge of its complementary variable, typically the phase, where knowledge of a variable is defined as its relative entropy with respect to the uniform distribution. In the case of finite-dimensional systems, a weighting of phase knowledge by a factor μ (> 1) is necessary in order to make the bound tight, essentially on account of the POVM nature of phase as defined here. Numerical and analytical evidence suggests that μ tends to 1 as the system dimension becomes infinite. We study the effect of non-dissipative and dissipative noise on these complementary variables for an oscillator as well as atomic systems. © 2010 World Scientific Publishing Company.

Fulltext

Modern Physics Letters B

Complementarity in generic open quantum systems

We have investigated the magnetoelectric and magnetodielectric response in FeVO4, which exhibits a change in magnetic structure coincident with ferroelectric ordering at TN2 ≈ 15 K. Using symmetry considerations, we construct a model for the possible magnetoelectric coupling in this system and present a discussion of the allowed spin structures in FeVO4. Based on this model, in which the spontaneous polarization is caused by a trilinear spin-phonon interaction, we experimentally explore the magnetoelectric coupling in FeVO4 thin films through measurements of the electric field-induced shift of the multiferroic phase transition temperature, which exhibits an increase of 0.25 K in an applied field of 4 MV/m. The strong spin-charge coupling in FeVO4 is also reflected in the significant magnetodielectric shift, which is present in the paramagnetic phase due to a quartic spin-phonon interaction and shows a marked enhancement with the onset of magnetic order which we attribute to the trilinear spin-phonon interaction. We observe a clear magnetic field-induced dielectric anomaly at lower temperatures, distinct from the sharp peak associated with the multiferroic transition, which we tentatively assign to a spin-reorientation crossover. We also present a magnetoelectric phase diagram for FeVO4. © 2010 The American Physical Society.

Magnetic structure and magnetoelectric coupling in bulk and thin film FeVO4

The effect of substituting Al for Si in Co36Fe36Si4-xAlxB20Nb4, (X=0, 0.5, 1.0, 1.5, 2.0 at%) alloys prepared in the form of melt-spun ribbons have been investigated. All the alloys were amorphous in their as-cast state. The onset of crystallization as observed using differential scanning calorimetry (DSC) was found to rise at low Al content up to X=1 at% beyond which there was a decreasing trend. The alloys also exhibited glass transition at 'Tg'. Microstructural studies of optimally annealed samples indicated finer dispersions of nanoparticles in amorphous matrix which were identified as bcc-(FeCo)Si and bcc-(FeCo)SiAl nanophases by X-ray diffraction technique. Alloy with optimum content of Al around X=1 at% exhibited stability in coercivity at elevated temperatures. Though Al addition is known to lower magnetostriction, such consistency in coercivity may also be attributed towards lowering in the nanoparticle size compared to X=0 alloy. In the nanostructured state, the alloy containing optimum Al content (X=1) exhibited further enhancement in ferromagnetic ordering or the Curie temperature by 100 K compared to alloy without Al. Such addition also attributed to better frequency response of coercivity and low core losses. © 2009 Elsevier B.V. All rights reserved.

Journal of Magnetism and Magnetic Materials

Enhancement in soft magnetic and ferromagnetic ordering behaviour through nanocrystallisation in Al substituted CoFeSiBNb alloys

5Cr-0.5Mo steel having initial bainitic microstructure has been aged at 600 °C for 5000 h and subjected to creep at 600 °C/60 MPa. At different lengths of time the tests were interrupted for magnetic measurement using magnetic Barkhausen emissions (MBE) and magnetic hysteresis loop (MHL) techniques. Composition, morphology and distribution of carbides were studied using scanning electron microscopy (SEM). Magnetic softness was observed in the material up to 1600 h of ageing due to the decrease in pinning density for the coarsening of carbides by accumulation of large number of finer carbides. At higher ageing periods the demagnetizing field offered by the large massive carbides causes magnetic hardening. During creep test since the material has been normalized at 50 h of creep test also the structural change in creep test is accelerated, the magnetic softening for the interstitial carbon migration to the grain boundary and stress relaxation has removed in such early periods of ageing. When the carbides started coarsening the number density of the carbides decreased and inter-carbide distance increased which enhances the magnetic softening in the material in the secondary stage of creep. Formation of massive carbides and micro voids at the late tertiary stage of creep offers demagnetizing field causes magnetic hardening before failure of the material. © 2009 Elsevier B.V. All rights reserved.

Study of high-temperature ageing and creep on bainitic 5Cr-0.5Mo steel by magnetic NDE techniques

We show that a fourth family of quarks with mt′ in the range of (400-600) GeV provides a rather simple explanation for the several indications of new physics that have been observed involving CP asymmetries of the b-quark. The built-in hierarchy of the 4 × 4 mixing matrix is such that the t′ readily provides a needed perturbation (≈ 15 %) to sin 2 β as measured in B → ψ Ks and simultaneously is the dominant source of CP asymmetry in Bs → ψ φ{symbol}. The correlation between CP asymmetries in Bs → ψ φ{symbol} and Bd → φ{symbol} Ks suggests mt′ ≈ (400 - 600) GeV. Such heavy masses point to the tantalizing possibility that the 4th family plays an important role in the electroweak symmetry breaking. © 2009 Elsevier B.V.

Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics

The fourth family: A simple explanation for the observed pattern of anomalies in B - CP asymmetries

We have investigated the effects of substituting In for Mn on the antiferromagnetic phase transition in Y MnO3 using magnetic, dielectric, and specific heat measurements. We prepared a set of isostructural phase pure hexagonal Y Mn1-xInxO3 samples having x = 0 to x = 0.9, which exhibit a systematic decrease of the antiferromagnetic ordering temperature with increasing In content. The multiferroic phase, which develops below TN, appears to be completely suppressed for x ≥ 0.5 in the temperature range investigated, which can be attributed solely to the dilution of magnetic interactions as the crystal structure remains hexagonal. Similarly to previous reports, we find an enhancement of the magnetocapacitive coupling on dilution with non-magnetic ions. © 2010 Elsevier Ltd. All rights reserved.

Solid State Communications

Suppression of multiferroic order in hexagonal YMn1 - x Inx O3 ceramics

We study the dynamics of entanglement in a two-qubit system interacting with a squeezed thermal bath via a dissipative system-reservoir interaction with the system and reservoir assumed to be in a separable initial state. The resulting entanglement is studied by making use of concurrence as well as a recently introduced measure of mixed state entanglement via a probability density function which gives a statistical and geometrical characterization of entanglement by exploring the entanglement content in the various subspaces spanning the two-qubit Hilbert space. We also make an application of the two-qubit dissipative dynamics to a simplified model of quantum repeaters. © 2010 Elsevier Inc. All rights reserved.

Annals of Physics

Dynamics of entanglement in two-qubit open system interacting with a squeezed thermal bath via dissipative interaction

We analyze the dynamics of entanglement in a two-qubit system interacting with an initially squeezed thermal environment via a quantum nondemolition system-reservoir interaction, with the system and reservoir assumed to be initially separable. We compare and contrast the decoherence of the two-qubit system in the case where the qubits are mutually close-by ('collective regime') or distant ('localized regime') with respect to the spatial variation of the environment. Sudden death of entanglement (as quantified by concurrence) is shown to occur in the localized case rather than in the collective case, where entanglement tends to 'ring down'. A consequence of the QND character of the interaction is that the time-evolved fidelity of a Bell state never falls below 1/√2, a fact that is useful for quantum communication applications like a quantum repeater. Using a novel quantification of mixed state entanglement, we show that there are noise regimes where even though entanglement vanishes, the state is still available for applications like NMR quantum computation, because of the presence of a pseudo-pure component. © 2009 EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg.

European Physical Journal D

Entanglement dynamics in two-qubit open system interacting with a squeezed thermal bath via quantum nondemolition interaction

We develop a unified, information theoretic interpretation of the number-phase complementarity that is applicable both to finite-dimensional (atomic) and infinite-dimensional (oscillator) systems. The relevant uncertainty principle is obtained as a lower bound on entropy excess, the difference between number entropy and phase knowledge, the latter defined as the relative entropy with respect to the uniform distribution. © 2010 Elsevier B.V. All rights reserved.