Fine-Tuning Quantum Materials: A New Approach Using Hydrogen Ions

Cover image courtesy: MIT/Ella Maru Studio

Quantum materials, with their exotic properties governed by quantum mechanics, hold immense potential for technological advancements. However, harnessing their full capabilities requires precise tuning, akin to fine-tuning a race car for optimal performance. A team led by Mingda Li, an associate professor in MIT’s Department of Nuclear Science and Engineering (NSE), has demonstrated a groundbreaking technique for achieving this precision.

Their approach focuses on manipulating the Fermi level, the highest energy level occupied by electrons in a material. By adjusting the Fermi level, researchers can significantly influence the material’s electronic properties. The team demonstrated their technique using a Weyl semimetal, a type of quantum material with unique electronic structures called Weyl nodes.

“When it comes to quantum materials, the Fermi level is practically everything,” Li emphasizes. “Many of the effects and behaviors that we seek only manifest themselves when the Fermi level is at the right location.”

The team’s method involves bombarding the material with negative hydrogen ions using MIT’s Tandem ion accelerator. These ions, being the smallest available, offer unparalleled precision in altering the material’s electronic properties.

“The use of advanced accelerator techniques allows for greater precision than was ever before possible, setting the Fermi level to milli-electron volt [thousandths of an electron volt] accuracy,” explains Kevin Woller, the principal research scientist leading the CSTAR lab where the accelerator is housed.

A key challenge lies in determining the precise duration of ion bombardment. To address this, the team developed a theoretical model that predicts the required number of hydrogen ions and the corresponding exposure time. This model, significantly less computationally intensive than conventional methods, has proven remarkably accurate.

The implications of this breakthrough are far-reaching. By precisely tuning the Fermi level, researchers could enhance the critical temperature for superconductivity, improve the efficiency of thermoelectric materials, and even advance quantum computing technologies.

Manasi Mandal, an NSE postdoc and lead author of the paper published in Applied Physics Reviews, highlights the technique’s versatility:

We can use this method for any inorganic bulk material, and for thin films as well.

Thomas Zac Ward, a senior scientist at Oak Ridge National Laboratory, lauds the research: “This work provides a new route for the experimental exploration of the critical, yet still poorly understood, behaviors of emerging materials. The ability to precisely control the Fermi level of a topological material is an important milestone that can help bring new quantum information and microelectronics device architectures to fruition.”

This innovative approach to fine-tuning quantum materials promises to unlock a new era of technological advancements, propelling us toward a future brimming with quantum possibilities.

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