This is a diagram of a 2-D spin-orbit coupling and topological band. Atoms perform the spin flip quantum tunneling in the optical lattice under the laser field. Credit: PAN's team
Considered one of the fundamental effects in quantum physics, spin-orbit coupling plays a significant role in several physic phenomena and exotic quantum states.
These phenomena are the foundation of a number of research fields in condensed-matter physics, such as topological superconductor, topological insulator and spintronics.
However, the issue related to uncontrollable complex environment has made research related to solid materials of exotic physics difficult. This continues to be a key challenge for several significant studies.
A joint team of researchers from the University of Science and Technology of China and Peking University recently made an advancement in quantum simulation of ultracold atoms. These researchers were the first to initiate both the proposal and realization of two-dimensional spin-orbit coupling for ultracold quantum gases.
This will inspire researches dealing with exotic topological quantum states and will also enhance the understanding of the world. The result obtained from this joint research was published as a Research Article on the recent issue of Science.
A review article was specially published on the corresponding perspectives column, based on the 'great potential for examining exotic phenomena that beyond conventional condensed-matter physics' of the result.
The spin-orbit coupling explains the interactions between the orbital motion and the particle spin. Synthesizing the spin-orbit coupling within ultracold atoms is considered to be the most exciting directions in the quantum simulation field.
A number of research teams from many countries in the past decade contributed to this especially challenging research field. Spielman's team from NIST were the first to realize 1D spin-orbit coupling. This was then followed by many other laboratories.
2D spin-orbit coupling was required to simulate the exotic topological quantum matter, as topological superconductor or insulator. However, the work carried out on spin-orbit coupling was considered to be extremely challenging.
LIU Xiongjun's theoretical team from Peking University first motivated and proposed the Raman optical lattice system, resulting in 2D spin-orbit coupling. Based on this theoretical concept, years of dedication on the ultra precision laser and magnetic field controlling technology was offered by the experimental team headed by PAN Jianwei, CHEN Shuai and DENG Youjin from the USTC. The Raman optical lattice quantum system was finally constructed by the team, following the synthesizing of the 2D spin-orbit coupling for Bose-Einstein condensates.
The review in Science described this setup as especially appealing as it deals with just one single laser source and does not need phase-locking between a number of optical beams. Instead, a single laser beam is divided into two parts in order to develop a frequency-shifted Raman beam and a spin-independent optical lattice.
Further studies highlight that the band topology and the spin-orbit coupling are majorly adjustable. This work will immensely influence the research to condensed-matter physics and ultracold atoms. Researches in the field of quantum computing can also draw inspiration from this new development. Within the next 10-15 years, scientists are hoping to understand the coherent manipulation of 80-100 quantum bit, solving speed of particular issues will go beyond the existing supercomputers.