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Our research direction
The conventional weakly correlated systems are often described by the interaction of a single electron with its environment, for example, semiconductors. In contrast, the properties of the so-called strongly correlated states are determined by the collective interaction of many electrons via their charges and spins. The complexity that arises from such interactions between many particles gives rise to many fascinating phenomena. This covers the long-range magnetic order to recent discoveries like superconductivity, colossal magnetoresistance, and topological magnetic or electric states. Owing to their multi-particle nature, the microscopic understanding of the ground state with such dominant strong-correlation phenomena is a demanding task. For a thorough understanding, it is thus indispensable, however, to go away from the ground state and study the dynamical behavior of such systems.
On one hand, the functionality of a device always results from bringing it away from its ground state. Nevertheless, studying the non-equilibrium behavior of the ground state reveals the microscopic processes at work, stabilizing a strongly correlated state. Over the last years, various experimental and theoretical tools have been rapidly improving, and strong-correlation dynamics are now in the process of establishing itself as a new and powerful branch in condensed-matter research. Because of the emerging nature of the field, research activities are still ambiguously diverse. Important advances are made in certain directions but at the same time, other aspects of crucial significance are disregarded — an overarching coherence of the field yet needs to be established.
The broad scope and extent of our research direction in NISER is to substantially promote this overarching coherence and contribute to building a solid foundation in the field of strong-correlation dynamics. The primary research topics involve, in a broad manner:
Coherent low-energy excitation of correlated states
Studying phase-resolved dynamics of elementary excitations.
Introduction to our research method
One of the most technologically unexploited regions of electromagnetic radiation, namely the terahertz (THz) radiation has gained a lot of attention from researchers across the world in the last decades. Needless to mention, today THz technology is being used for a wide range of applications. Some of these include information and communications technology, medical sciences, security, quality control, and non-destructive imaging. The most significant advancement is in the direction of availing robust sources and efficient detectors, paving the way towards spectroscopy. The development of THz (then known as far-infrared) time-domain spectroscopy (THz-TDS) is a milestone that has pushed a new direction of fundamental THz research. Due to low THz photon energies (approx. 4 meV at 1THz), these radiations provide a means to address electronic states by resonant excitation and detection in any material systems where such electronic states have energy differences in the meV range. Further, the development of different techniques for the generation of intense THz pulses and nonlinear THz spectroscopy has revealed the means to explore new categories of THz-induced nonlinear phenomena and nonlinear effects in various materials. Typically, intense THz pulses have the potential to induce ultrafast electric- or magnetic-switching operations that last from a few tens of femtoseconds to a few tens of picoseconds. Such intense pulses also bear the potential to drive the resonant couplings between various fundamental excitations in different classes of exotic material systems.
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