The team creates ‘quantum composites’ for various electrical and optical innovations

(Nanowerk News) UCR’s team of electrical engineers and materials scientists demonstrated research breakthroughs that could lead to far-reaching advances in electrical, optical, and computer technology.

The research group of the College of Engineering Marlan and Rosemary Bourns, led by renowned professor Alexander Balandin, has demonstrated in the laboratory the unique and practical functions of a newly created material, which they call quantum composites.

These composites consist of small crystals called “charge density wave quantum materials” incorporated in a polymeric matrix (large molecules with repeating structures). Upon heating or exposure to light, the charge density wave material undergoes a phase transition leading to the unusual electrical response of the composite.

Compared to other materials that reveal quantum phenomena, the quantum composites fabricated by the Balandin group exhibit functionality over a much wider temperature range and have a greatly increased ability to store electricity, giving them excellent potential uses.

University of California, Riverside, researchers describe the unique trait in a paper published in the journal Advanced Materials (“Quantum Composites with Wave-Density Charge”). The lead authors of the paper are Zahra Barani and Tekwam Geremew, UCR graduate students with the Department of Electrical and Computer Engineering, who synthesized and tested the composites. Another UCR graduate student, Maedeh Taheri, is a co-author on electrical measurements. Balandin and Fariborz Kargar, assistant professor and project scientist, are corresponding authors.

The term quantum refers to materials and devices in which electrons behave more like waves than particles. The wave nature of electrons can give materials that are used in new generations of computer, electronics, and optical technologies unusual properties.

Materials that reveal quantum phenomena were sought to build quantum computers that surpassed the limitations of most of today’s computations based on chips that use binary bits for computation. The material is also being sought for super sensitive sensors used for a variety of electronic and optical applications.

But materials with quantum phenomena have a big drawback, says Balandin.

“The problem with these materials is that the phenomenon is quantum fragile and usually observed only at very low temperatures,” he said. “Defects and impurities destroy the wave function of the electron.”

Remarkably, the charge density wave material in the quantum composite fabricated by Balandin’s lab exhibits functionality as high as 50 °C above room temperature. This transition temperature is close to the operating temperature of computers and other electronic gadgets, which heat up during operation. This temperature tolerance opens up possibilities for a wide range of applications of quantum composites in electronics and energy storage.

The researchers also found that quantum composites have an unusually high dielectric constant – a metric that characterizes a material’s ability to store electricity. The dielectric constant of electrically insulating composites more than doubles, which allows smaller, more powerful capacitors to be used for energy storage.

“Energy storage capacitors can be found in battery-powered applications,” said Balandin. “Capacitors can be used to transmit peak power and provide energy for computer memory during an unexpected shutdown. Capacitors can charge and discharge faster than batteries. To expand the use of capacitors for energy storage, an increase in energy per volume is required. Our quantum composite materials can help achieve this goal.”

Another possible application for quantum composites is reflective coatings. Changes in the dielectric constant induced by heating, exposure to light, or the application of an electric field can be used to change the reflection of light from glass and windows coated with such composites.

“We hope that our ability to maintain the quantum condensate phase in charge-density wave materials even inside disordered composites and even above room temperature can be a game changer for many applications. This is a conceptually different approach to tuning the properties of the composites we use in our daily lives,” added Balandin.