Newswise —

A group of UCR electrical engineers and material scientists exhibited a research discovery that could lead to extensive progressions in electrical, optical, and computer technologies.

Distinguished professor Alexander Balandin's research group at the Marlan and Rosemary Bourns College of Engineering has demonstrated the practical and distinctive capabilities of recently developed materials, named quantum composites, in their laboratory.

The quantum composites comprise of tiny crystals of "charge density wave quantum materials" embedded in a polymer matrix, which are molecules with large repeating structures. When exposed to heat or light, the charge density wave material undergoes a phase transition that results in an exceptional electrical reaction of the composites.

In comparison to other materials that exhibit quantum phenomena, the quantum composites produced by Balandin's team showcased functionality over a broader range of temperatures and had a significantly enhanced capacity for electrical storage, indicating their remarkable potential for practical application.

The distinct features of the quantum composites have been detailed by the researchers at the University of California, Riverside in a publication titled "Quantum Composites with Charge-Density-Wave Fillers" in the journal Advanced Materials. UCR graduate students Zahra Barani and Tekwam Geremew, from the Department of Electrical and Computer Engineering, who created and assessed the composites, are the lead authors of the paper. Maedeh Taheri, another UCR graduate student, assisted with the electrical measurements and is a co-author. The corresponding authors of the paper are Balandin and Fariborz Kargar, an assistant adjunct professor and project scientist.

The term "quantum" pertains to materials and devices in which electrons exhibit wave-like behavior rather than behaving like particles. The wave-like nature of electrons can impart unique properties to materials, which are utilized in the development of a new era of computer, electronic, and optical technologies.

Materials that exhibit quantum phenomena are highly sought after for the construction of quantum computers, which can transcend the limitations of conventional computing based on chips using binary bits for computations. These materials are also extensively used in the development of ultra-sensitive sensors, which find applications in various electronic and optical domains.

But the materials with quantum phenomena have major drawbacks, Balandin said.

“The problem with these materials is that the quantum phenomena are fragile and typically observed only at extremely low temperatures,” he said. “The defects and impurities destroy the electron wave function.” 

What's remarkable is that the charge density wave material in the quantum composites fabricated by Balandin's laboratory displayed functionality that extended up to 50°C above the room temperature. This transition temperature is comparable to the operating temperature of computers and other electronic devices that heat up during their operation. This high-temperature tolerance provides a possibility for an extensive array of applications of quantum composites in the fields of electronics and energy storage.

Additionally, the researchers discovered that quantum composites possess an exceptionally high dielectric constant, which is a measure of the material's capacity for storing electricity. The electrically insulating composites demonstrated an increase in dielectric constant of more than two orders of magnitude, thereby enabling the development of smaller and more efficient capacitors that are utilized for energy storage.

Balandin explained that "Energy storage capacitors are commonly employed in battery-powered applications. They can provide peak power and energy for computer memory in case of unexpected shutdowns. Capacitors can charge and discharge at a faster rate as compared to batteries. In order to enhance the use of capacitors for energy storage, it is necessary to increase the energy density. Our quantum composite material can assist in achieving this objective."

Quantum composites also have the potential to be utilized as reflective coatings. The alteration in the dielectric constant caused by the application of an electrical field, light exposure, or heating can be employed to modify the light reflection from glasses and windows coated with such composites.

Balandin stated that "We are optimistic that our ability to maintain the quantum condensate phases in charge-density-wave materials even within disordered composites and at temperatures exceeding room temperature can revolutionize many applications. It represents a distinct conceptual approach for modifying the properties of composites that we frequently use in our daily lives."

The UCR team collaborated with other researchers for this study, including Megan Stokey, Matthew Hilfiker, and Mathias Schubert from the University of Nebraska who conducted some of the optical measurements. They also worked with Nicholas Sesing and Tina Salguero from the University of Georgia who synthesized a key material used in the composite preparation at UCR.

Journal Link: Advanced Materials