Scientists create stable 'boron graphene' and uncover quantum liquid crystal state

Scientists create stable 'boron graphene' and uncover quantum liquid crystal state

Researchers at Tohoku University have developed a stable version of "boron graphene," a material previously considered nearly impossible to manufacture. The team achieved this by extracting a two-dimensional boron layer from within a three-dimensional crystal, leading to the discovery of a quantum state that mimics the behavior of liquid crystals.

The study, published in Science Advances on July 2, 2026, addresses a long-standing limitation of graphene. While graphene is a primary candidate for future electronics, its electron interactions are relatively weak, which has hindered its use in high-temperature superconductors. Scientists have long sought borophene — a two-dimensional sheet of boron atoms — because it possesses stronger electron interactions capable of producing exotic quantum phenomena.

However, the ideal honeycomb structure of borophene is extremely unstable in free-standing form. To bypass this, Takafumi Sato of Tohoku University’s Advanced Institute for Materials Research (WPI-AIMR) and his colleagues utilized a stable three-dimensional crystal known as LaRh3B2.

"We demonstrated a fundamentally new way of creating two-dimensional quantum materials,"

Takafumi Sato, WPI-AIMR, via wpi-aimr.tohoku.ac.jp

Rather than synthesizing a fragile sheet from scratch, the researchers exposed a naturally occurring honeycomb boron layer already present within the LaRh3B2 crystal structure. This method created a stable two-dimensional electronic system that retains the properties of the elusive boron graphene.

Uncovering the Electronic Nematic State

To analyze the material, the team employed two distinct imaging techniques. Using angle-resolved photoemission spectroscopy (ARPES) at synchrotron radiation facilities, they identified a van Hove singularity, an unusually high concentration of electrons near the material’s Fermi level. This singularity strengthens electron interactions, which can trigger unusual quantum behavior.

The researchers paired these findings with scanning tunneling microscopy and spectroscopy (STM/STS) to observe electrons in real space. This combination revealed that electrons spontaneously align in one preferred direction. In doing so, they break the crystal's original six-fold symmetry and form what is called an electronic nematic state.

In this state, electrons behave similarly to the molecules found in a liquid crystal display. While a standard honeycomb lattice has six-fold rotational symmetry, meaning it overlaps with itself after a 60-degree rotation, the electronic nematic state is elongated horizontally. This results in a two-fold symmetric state that only overlaps with itself after a 180-degree rotation.

"Neither technique alone could have revealed the full picture,"

Kosuke Nakayama, assistant professor at Graduate School of Science, via wpi-aimr.tohoku.ac.jp

Nakayama stated that the synergy between momentum-space information from ARPES and real-space observations from STM was essential to connect the electronic instability to the emergence of the nematic state.

Future Implications for Quantum Tech

Sato noted that observing this liquid crystal state in a graphene-like material proves that carefully designing a material's electronic structure can unlock new quantum phenomena.

The discovery provides a versatile platform for further research because the crystal family used in the study allows for the substitution of many of its chemical elements. This allows scientists to readily adjust the behavior and number of electrons within the material.

The researchers suggest this flexibility could accelerate the development of energy-saving quantum technologies and next-generation superconductors. The study was authored by a team including Takemi Kato, Tomonori Nakamura, Kosuke Nakayama, Takumi Osumi, Seigo Souma, Asuka Honma, Alexandre Antezak, Pedro Rezende Gonçalves, Kiyohisa Tanaka, Miho Kitamura, Kenichi Ozawa, Koji Horiba, Hiroshi Kumigashira, Takashi Takahashi, Franck Fortuna, Andres Felipe Santander-Syro, Rikio Settai, Yoshichika Onuki, Yoshinori Okada, and Takafumi Sato.