Field theory and Quantum Phase transitions
S. Shankaranarayanan
One of the key results of quantum mechanics is that fluctuations occur at absolute zero temperature. While at higher temperatures the strength of these zero-point fluctuations are small compared to the thermal fluctuations. However, at very low temperatures quantum fluctuations can become sufficiently strong, the system undergoes a new kind of phase transition called quantum phase transition. These transitions are beyond the Ginzburg-Landau-Wilson paradigm of second-order phase transitions at finite temperatures. Understanding these transitions may help us understand antiferromagnetic heavy fermions, superconductor-insulator transition in two-dimensional systems.
Over the last few years, one of the key theoretical research areas has been to identify a physical quantity whose divergence signal quantum phase transition. Entanglement entropy has emerged as a key theoretical resource in this direction. Our group has shown that it is possible to understand certain quantum phase transitions with linear, higher derivative quantum field theories (S. Ghosh and S. Shankaranarayanan, Phys. Rev. D. 86, 125011 (2012)). We plan to compute the entanglement entropy with higher accuracy in order to identify these phase transition precisely.