Three-dimensional quantum Hall effect and metal-insulator transition in ZrTe5

Understand

Symmetry, dimensionality, and interaction are crucial ingredients for phase transitions and quantum states of matter.

• As a prominent example, the integer quantum Hall effect (QHE) represents a topological phase generally regarded as characteristic for two-dimensional (2D) electronic systems, and its many aspects can be understood without invoking electron-electron interaction.
• The intriguing possibility of generalizing QHE to three-dimensional (3D) systems was proposed decades ago, yet it remains elusive experimentally.
• Here, we report clear experimental evidence for the 3D QHE observed in bulk ZrTe5 crystals.