Seminars & Lectures
| * TITLE | Phase Structure of the Topological Anderson Insulator | ||||||
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| * DATE / TIME | 2012-02-17, 10:30AM | ||||||
| * PLACE | 512 Seminar room, APCTP Headquarters | ||||||
| * ABSTRACT | |||||||
| We study the disordered topological anderson insulator in a 2-D (square not strip) geometry. We first report the phase diagram of finite systems and then study the evolution of phase boundaries when the system size is increased. We establish that conductance quantization can occur without a bulk band gap, and that there are two phases with quantized conductance: TAI-I with a bulk band gap, and TAI-II with localized bulk states. Effective medium theory (CPA, SCBA) predicts well the boundaries and interior of the gapped TAI-I phase, but fails to predict all boundaries save one of the ungapped TAI-II phase. Even in large $1120 times 1120$ samples there are direct transitions from bulk conduction into both the gapped TAI-I and the ungapped TAI-II phases without an intervening insulating phase. The TAI-II transition manifests scale invariance while the remarkably stable TAI-I transition does not. There is no metallic phase at the transition between quantized and insulating phases. Centered near this transition there are very broad peaks in the eigenstate size and fractal dimension $d_2$; in a large portion of the conductance plateau eigenstates grow when the disorder strength is increased. The fractal dimension at the peak maximum is $d_2 approx 1.5$. We report conductance distributions near several phase transitions and compare them with critical conductance distributions for well-known models. |
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