Straintronic control of correlations in twisted van der Waals heterostructures

Introduction

Correlations and topology are the cornerstones of modern condensed matter physics, and their coexistence is believed to lead to novel quantum electronic devices with built-in information protection.

Background

In the landmark discoveries of previous years, it has been found that in 2D materials placed on top of each other at a magic rotation angle, correlated phases appear. In contrast to high-Tc materials, in twisted van der Waals materials, correlation effects are coupled with topology. Thanks to their gate tunability, the exploration of their phase diagram takes only days instead of years.

This has led to the discovery of a multitude of correlated phases, including:

• Correlated insulators
• Orbital magnetic phases
• Non-conventional superconducting phases
• Ferroelectric phases

Despite the immense interest, the understanding of their behavior at the microscopic level is limited, which calls for further experiments and novel experimental tools.

Project Goals

In this project, we will implement techniques that are radically new in this field: hydrostatic pressure and mechanical strain to uncover the ground state properties of twisted graphene and transition metal dichalcogenide heterostructures.

Since the interlayer coupling plays the dominant role, changing the distance of the layers with hydrostatic pressure has a dramatic effect on the band structure and the correlated phases that emerge. The symmetries of the system can be deterministically broken by strain patterns applied in-situ.

Expected Outcomes

This very timely project will lead to several breakthroughs, including:

1. Revealing the ground state of twisted bilayer graphene at different filling factors from the large set of competing phases.
2. In-situ engineering of the topology of these systems.
3. Tuning quantum phase transitions between non-Fermi liquid phases.

The highly challenging research concept relies on my unique background in sample fabrication, quantum transport under strain and pressure, and studies on correlated and topological systems.