The struggle to keep drinks cold during the summer is a lesson in classical phase transitions. To study phase transitions, apply heat to a substance and watch how its properties change. Add heat to water, and at the so-called "critical point," watch as it transforms into a gas (steam). Remove heat from water and watch it turn into a solid (ice). Now, imagine that you've cooled everything down to very low temperatures -- so low that all thermal effects vanish. Welcome to the quantum realm, where pressure and magnetic fields cause new phases to emerge in a phenomenon called quantum phase transitions (QPT). More than a simple transition from one phase to another, QPT form completely new properties, such as superconductivity, in certain materials. Now, a group of physicists, led by University of Utah professor Andrey Rogachev, has discovered that superconducting nanowires made of MoGe alloy undergo quantum phase transitions from a superconducting to a normal metal state when placed in an increasing magnetic field at low temperatures. The study is the first to uncover the microscopic process by which the material loses its superconductivity; the magnetic field breaks apart pairs of electrons, called Cooper pairs, which interact with other Cooper pairs and experience a damping force from unpaired electrons present in the system.
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