Caltech researchers recently used a synchrotron X-ray source to investigate the existence of instabilities in the arrangement of the electrons in metals as a function of both temperature and pressure, and to pinpoint, for the first time, how those instabilities arise.
The researchers used the X-ray beams to investigate charge-order effects in two metals, chromium and niobium diselenide, at pressures ranging from 0 (a vacuum) to 100 kilobar (100,000 times normal atmospheric pressure) and at temperatures ranging from 3 to 300 K (or -454 to 80 degrees Fahrenheit). Niobium diselenide was selected because it has a high degree of charge order, while chromium, in contrast, has a high degree of spin order.
The researchers found that there is a simple correlation between pressure and how the communal electrons organize themselves within the crystal. Materials with completely different types of crystal structures all behave similarly. "These sorts of charge- and spin-order phenomena have been known for a long time, but their underlying mechanisms have not been understood until now," says Rosenbaum.
![]()
One of the metallic samples studied, niobium diselenide, is seen here–the square in the center–as prepared for an X-ray diffraction experiment. Credit: University of Chicago/Argonne National Laborator
Nature Physics - Itinerant density wave instabilities at classical and quantum critical points
Read more »![]()
![]()
![]()
![]()
![]()
![]()
![]()
![]()
![]()
![]()
![]()
The researchers used the X-ray beams to investigate charge-order effects in two metals, chromium and niobium diselenide, at pressures ranging from 0 (a vacuum) to 100 kilobar (100,000 times normal atmospheric pressure) and at temperatures ranging from 3 to 300 K (or -454 to 80 degrees Fahrenheit). Niobium diselenide was selected because it has a high degree of charge order, while chromium, in contrast, has a high degree of spin order.
The researchers found that there is a simple correlation between pressure and how the communal electrons organize themselves within the crystal. Materials with completely different types of crystal structures all behave similarly. "These sorts of charge- and spin-order phenomena have been known for a long time, but their underlying mechanisms have not been understood until now," says Rosenbaum.
One of the metallic samples studied, niobium diselenide, is seen here–the square in the center–as prepared for an X-ray diffraction experiment. Credit: University of Chicago/Argonne National Laborator
Nature Physics - Itinerant density wave instabilities at classical and quantum critical points
Read more »
