Advanced computational tools for understanding quantum materials

Researchers at the University of Chicago’s Pritzker School of Molecular Engineering (PME), Argonne National Laboratory, the University of Modena, and the University of Reggio Emilia have developed a new computational tool to describe how atoms in quantum materials absorb and Behavior when emitting light.

The tool will be released as part of the open source software package WEST, developed by a team led by Professor Marco Govoni within the Midwest Center for Computational Materials Integration (MICCoM), to help scientists better understand and design new quantum materials. technology.

“What we have done is expand scientists’ ability to study these materials for use in quantum technologies,” said Giulia Galli, Liu Family Professor of Molecular Engineering and senior author of the paper, which appears in Journal of Chemical Theory and Computation. “We can now study systems and properties that really weren’t accessible at scale in the past.”

Galli’s team demonstrated the accuracy of the tool, called WEST-TDDFT (empty-state time-dependent density functional theory), in studying three different semiconductor materials, but said it could be applied to a wide range of related materials and software have been developed to operate at scale on a variety of high-performance architectures.

Quantum Information Construction Module

The basic unit of information in powerful new quantum technologies is the qubit. Unlike bits in classical computing, which only use 0s and 1s to encode data, qubits can also exist in a superposition state, representing both 0s and 1s.

Tiny defects in materials, such as missing or substituted atoms in the lattice of a crystal structure, can assume quantum states and function as qubits. These qubits are extremely sensitive to the electrical, optical and magnetic properties of their surroundings, allowing them to function as sensors.

Understanding exactly how these “point defects” interact with photons to change their energy state could allow researchers to better manipulate them or design materials that use qubits as sensors or data storage units.

“How these materials absorb and emit light is critical to understanding how they function in quantum applications,” Galli said. “Light is how you look at these materials.”

Until now, researchers could predict the absorption and emission of light from point defects, but could not fully explain some of the atomic processes that occur when materials are in excited states, especially in the case of large, complex systems.

Simplify complex calculations

The quantum mechanical equations that must be solved to determine the atomic properties of materials are very complex and require a lot of computing power. In new work, Galli’s team has coded a new way to solve such equations more efficiently than in the past, while demonstrating that they are still accurate.

The increased speed and efficiency with which equations are now solved means they can be more easily applied to larger systems. In the past, the computational time and power required to analyze these systems made it unfeasible.

“Through these methods, we can study the interaction of light and materials in quite large systems, which means that these systems are closer to the experimental systems actually used in the laboratory,” said Yu Jin, the first author of the paper and a graduate student. . New article.

The efficient method developed by the team can operate on two different computer architectures: central processing unit (CPU) and graphics processing unit (GPU). The researchers used it to study the excited-state properties of point defects in three materials: diamond, 4H silicon carbide and magnesium oxide. They found that the tool could efficiently calculate the properties of these systems, even if they have hundreds or thousands of atoms.

broader goals

The MICCoM team that developed WEST includes Dr. Victor Yu, Yu Jin and Professor Marco Govoni. The team is continuing to apply and fine-tune algorithms available in the software package, including WEST-TDDFT, to study a wide range of materials, not only for quantum technologies, but also for low-power and energy applications.

“We found a way to more efficiently solve the equations describing light emission and absorption so that they can be applied to real-world systems,” Govoni said. “We demonstrated that the method is both efficient and accurate.”

The new tools fit in with the Galli lab’s broader goals of researching and designing new quantum materials. Additionally, this month, they published new results showing how spin defects close to the surface of a material behave differently from spin defects deeper inside the material, depending on how the surface is terminated. Their results have implications for the design of quantum sensors that rely on spin defects.

The team also recently published a paper npj computational materialsexamines the properties of ferroelectric materials used in neuromorphic computing.