The Joint Condensed Matter Seminar (JCMS) series is organised by KTH Royal Insitute of Technology, Nordita, and Stockholm University.
On Monday, September 5th, 2022 from 11 am to 12 am we will host a seminar by Sudhansu Sekhar Mandal from the Indian Institute of Technology, Kharagpur.
Personal webpage.
Anomalous Re-entrant Quantized 5/2 Fractional Quantum Hall State
Although most of the fractional quantum Hall effect (FQHE) states in the lowest Landau level are well understood in terms of the composite fermion theory, the FQHE states in the second Landau level remain enigmatic. Amongst these, 5/2 state is the most intriguing as it is the cooperative system where the existence of Majorana edge mode was first proposed. Thermal Hall conductance [1] and shot-noise [2] experiments are in favour of the existence of such modes. However, the experimentally found topological order (on which the above quantities depend) is reported to be different from the theoretically predicted topological order for small or no Landau-level-mixing (LLM) which induces three-body interaction. Our exact-diagonalization study [3] reveals a topological phase transition from conventional low LLM phase to an anomalous re-entrant phase at higher LLM strength. Our predicted wave function which is found to have very high overlap with the exact ground state in this phase is a simple representative wave function for understanding this topological order. This wave function may be interpreted as two repulsive Bose-Einstein condensates of the composite bosons. However, there is no physical segregation between these two condensates because a complete symmetrisation of the composite bosons is explicitly considered. We attribute this novel phase to the experimentally observed topological order. We argue that the thermal Hall conductivity predicted by the wave function as \(\kappa_H = 2.5 \bigl( \frac{\pi^2 k_B^2 T}{3h} \bigr)\), as reported in the experiment.
[1] Banerjee et al, Nature (London) 559, 205 (2018).
[2] Dutta et al, Science 375, 193 (2022).
[3] S. Das, S. Das, and S. S. Mandal, arXiv:2206.04419.