Quantum mapmakers complete first voyage through spin liquid

31 March 2011

Scientists from Oxford University and the Rutherford Appleton Laboratory have completed a painstaking mapping of one of the most exotic places in the universe found close to absolute zero. The ‘quantum spin liquid’ is a strange state of matter whose existence was proposed in the 1970s but which has only been observed recently. Until now, there has been extremely limited information available describing its physical characteristics. The new research, published in the science journal Nature, demonstrates the effect of temperature and magnetic field on this delicate state of matter. The measurements were made by implanting muons into the spin liquid in order to measure the microscopic magnetism.

The quantum spin liquid state is found in 70 milligrams of tiny black crystals of an organic material cooled to just a couple of hundredths of a degree above absolute zero. Inside the material, magnetic atoms are arranged on triangular grids and behave as “quantum spins”. The interactions between these spins make them liquid-like, never freezing into one configuration, even at temperatures approaching absolute zero. This behaviour is completely different to the more familiar magnets found in everyday life in which, at some particular temperature, the quantum spins become locked into a particular configuration.

Oxford team members: Tom Lancaster and Stephen Blundell