Scaling behavior of the quantum phase transition from a quantum-anomalous-Hall insulator to an axion insulator

Xinyu Wu,Cui-Zu Chang,Xi Lin,Moses H W Chan,Chui-Zhen Chen,Jian Sun,Nitin Samarth,Ling Zhang,X C Xie,Di Xiao

doi:10.1038/s41467-020-18312-z

Abstract

The phase transitions from one plateau to the next plateau or to an insulator in quantum Hall and quantum anomalous Hall (QAH) systems have revealed universal scaling behaviors. A magnetic-field-driven quantum phase transition from a QAH insulator to an axion insulator was recently demonstrated in magnetic topological insulator sandwich samples. Here, we show that the temperature dependence of the derivative of the longitudinal resistance on magnetic field at the transition point follows a characteristic power-law that indicates a universal scaling behavior for the QAH to axion insulator phase transition. Similar to the quantum Hall plateau to plateau transition, the QAH to axion insulator transition can also be understood by the Chalker–Coddington network model. We extract a critical exponent κ ~ 0.38 ± 0.02 in agreement with recent high-precision numerical results on the correlation length exponent of the Chalker–Coddington model at ν ~ 2.6, rather than the generally-accepted value of 2.33.

Highlights

The phase transitions from one plateau to the plateau or to an insulator in quantum Hall and quantum anomalous Hall (QAH) systems have revealed universal scaling behaviors
We found the temperature dependence of the derivative of the longitudinal resistance Rxx on the magnetic field B evaluated at the critical field Bc follows a characteristic powerlaw behavior, i.e. ðddRBxxÞB1⁄4Bc / TÀκ
The samples are 3QL (Bi, Sb)1.89V0.11Te3/5QL (Bi, Sb)2Te3/3QL (Bi, Sb)1.85Cr0.15Te3 sandwich heterostructures. These samples were grown on 0.5 mm-thick heat-treated SrTiO3 (111) substrate in a molecular beam epitaxy (MBE) chamber with a base vacuum of 2 × 10−10 mbar

Summary

Introduction

The phase transitions from one plateau to the plateau or to an insulator in quantum Hall and quantum anomalous Hall (QAH) systems have revealed universal scaling behaviors. We show that the temperature dependence of the derivative of the longitudinal resistance on magnetic field at the transition point follows a characteristic power-law that indicates a universal scaling behavior for the QAH to axion insulator phase transition. The study of quantum phase transitions is a rich topic of research in condensed matter physics Quantum phase transitions, such as the plateau-to-plateau transition in the quantum Hall (QH) effect at high magnetic field, can be accessed by varying only one physical parameter (e.g., magnetic field) near absolute zero temperature[1]. We studied the scaling behavior of the quantum phase transition from the QAH insulator to the axion insulator in magnetic TI sandwich samples in the temperature range between 45 and 100 mK. By analyzing the temperature dependence of R12, we probed two different insulating behaviors in two adjacent temperature ranges, validating the reliability of our scaling study for the QAH to axion insulator transition

Methods

Results

Conclusion