Regensburg 2025 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 12: Quantum Transport and Quantum Hall Effects (joint session HL/TT)

HL 12.3: Talk

Monday, March 17, 2025, 17:15–17:30, H15

Time-reversal invariant Chalker-Coddington model and the real-space renormalisation group — •Syl Shaw and Rudolf A. Römer — Department of Physics, University of Warwick, Coventry, CV4 7AL, UK

The Chalker-Coddington model has been utilised to great success in understanding the plateau transitions in the quantum Hall effect. Since the model’s inception, it has been extended to a time-reversal invariant symmetry class to describe the quantum-spin Hall effect. Here we adapt a real-space renormalisation group method[1] to respect time-reversal symmetry and use it investigate the phase diagram of the quantum-spin Hall effect. We aim to find distinct phases as a function of both saddle-point height, z and spin-mixing angle φ. At the phase boundary between insulator and metal, we compute the value of the critical exponent of the localisation length, ν, with the same real-space renormalisation technique. [1] S. Shaw, R. A. Römer Physica E 165, 116073 (2025)

Keywords: real-space renormalisation; quantum hall; time-reversal invariant; Chalker-Coddington; phase transition