Quantum Materials

Quantum materials are classified as materials where quantum effects dominate over larger energy and length scales. In a quantum state, macroscopic properties of materials are governed by ground-state quantum fluctuations in which information is propagated in a correlated manner with temporal evolution. Due to quantum correlations, these materials have a memory to distinguish their widely differing initial conditions, i.e., properties depend on initial conditions. At finite temperatures, thermalization erases the memory of a quantum system by dephasing the quantum correlation. Thermalization puts a limit on the experimental realization of quantum information. This poses the biggest bottleneck in realizing the potential of these materials for their application as quantum devices. Recently, the experimental realization of scrambled quantum information in atomic and bi-particle quantum systems triggered a new hope for studying the exotic quantum behavior of other quantum materials. A new class of quantum materials, e.g., topological insulators, graphene, Weyl semimetals, superconductors, quantum spin liquids, and spin ices, have found a prominent place in the literature. Rare earth titanates (R2Ti2O7) are one the most studied quantum materials having exotic low-temperature magnetic properties, e.g., spin ice (R=Ho, Dy), spin liquid (R=Tb), and antiferromagnetic ordering (R= Er, Gd). The experimental finding suggests that Ho2Ti2O7 and Dy2Ti2O7 spin ices have multiple ferroelectric transitions of different origins. Apart from the emergence of the dielectric relaxations, the magnetic behavior also shows multiple spin freezing in these materials. The behavior becomes more prominent when one deals with them in a regime where semi-classical phenomena are dominant. Fundamentally classical spin ice, which can descend to quantum spin liquid where quantum fluctuations upon the spin ice states, rule out the possibility of any long-range ordering down to zero temperature. Our group has investigated the emergence of quantum critical point and likely quantum phase transition in the rare earth (RE) pyrochlore, which makes these magnetically frustrated systems an interesting material to investigate further from both points of view, i.e., electronic, dielectric, and magnetic response and their possible coupling.

Key Publications:

  1. Evidence of Griffith phase in Quantum critical region of Dy2Ti1.8Mn0.2O7 R. M. Shukla, R. Sain, Martin Tolkiehn, Chandan Upadhyay Journal of Magnetism and Magnetic Materials, 556, 170308 (2022)

  2. Robust spin-ice freezing in magnetically frustrated Ho2GexTi2-xO7 pyrochlore, M Shukla, R Upadhyay, M Tolkiehn, Chandan Upadhyay Journal of Physics: Condensed Matter 32 (46), 465804 (2020)
  3. Role of Chemical Pressure on Optical and Electronic Structure of Ho2GexTi2-xO7 M. Shukla, S. Banik, R. Pandey, Chandan Upadhyay, Journal of Physics: Condensed Matter 32 (11), 115501 (2020)
  4. Signature of Correlated Quantum Tunneling and Thermal dephasing in Quantum-Classical Coupled Ho2Ti2O7 and Dy2Ti2O7 Spin Ices PK Yadav, Chandan Upadhyay Journal of Magnetism and Magnetic Materials, 498 166133 (2020)
  5. Effect of B-site substitution on structural, magnetic and optical properties of Ho2Ti2O7 pyrochlore oxide, PK Yadav, P Singh, M Shukla, S Banik, Chandan Upadhyay Journal of Physics and Chemistry of Solids, 138 109267 (2020)
  6. Dielectric relaxations in Ho2Ti2O7 and Dy2Ti2O7 pyrochlores, PK Yadav, M Tolkiehn, Chandan Upadhyay, Journal of Physics and Chemistry of Solids 134, 201-208 (2019)
  7. Quantum Criticality in geometrically frustrated Ho2Ti2O7 and Dy2Ti2O7 spin ices, PK Yadav, Chandan Upadhyay Journal of Magnetism and Magnetic Materials 482, 44-49 (2019)

Static and dynamic magnetic properties of Nanoparticles:

The magnetization dynamics associated with the iron oxide nanomaterials have been the focus of considerable interest from both elementary understanding and potential applications over the decades. Magnetite nanoparticles have drawn significant technological attention due to their efficient clinical applications. Integrating these magnetic nanomaterials with an optically active material, such as gold or silver, in the form of a core-shell nanostructure makes them quite efficient to be used as multimodal agents. Applying these materials in the biomedical field requires a lot of investigation into their structural, optical, and magnetic properties. The group is involved in the studies of these materials, associated properties, and applications.

Key Publications:

  1. Signatures of consolidated superparamagnetic and spin-glass behavior in magnetite-silver core-shell nanoparticles P Singh, M Shukla, Chandan Upadhyay Nanoscale 10, 22583-22592 (2018)
  2. Novel facets of multifunctional Ag@Fe3O4 core-shell nanoparticles for multimodal imaging applications, P Singh, BK Gupta, NK Prasad, PK Yadav, Chandan Upadhyay Journal of Applied Physics 124 (7), 074901 (2018).
  3. Role of Silver Nanoshells on Structural and Magnetic Behavior of Fe3O4 nanoparticles, P Singh, Chandan Upadhyay, Journal of Magnetism and Magnetic Materials. 458, 39-47 (2018).
  4. Size selectivity of magnetite core-(Ag/Au) shell nanoparticles for multimodal imaging applications P. Singh, Chandan Upadhyay, Materials Research Express 4 (2017), 105401