Using magnetic fields of over 90 T, the effective mass in the high-Tc superconductor YBa2Cu3O6+x was shown to be strongly enhanced as the material is doped toward optimal Tc.
First, some background
Superconductors are materials that, under certain conditions, conduct electricity with zero resistance. Superconductivity only occurs under certain conditions and can be destroyed if the temperature is too high or within a high magnetic field.
What is the finding?
Unconventional superconductivity, where Cooper pairing is driven by something other than electron coupling, is not well understood.
Researchers working on the high-temperature superconductor YBa2Cu3O6+x found that the effective mass of the material is enhanced as the material is changed chemically (or doped) toward the temperature where the material begins to superconduct. This is a common signature of increased electron-electron interactions in the area of a quantum critical point.
High-Tc cuprates lack a magnetic transition near optimal Tc, but may instead have a different type of Quantum critical point that drives superconductivity.
Why is this important?
High-temperature superconductors have been a thriving field of research for almost 30 years, however, evidence of a quantum critical point – the moment a material makes the decision to superconduct – has not yet been found.
Understanding the physics behind these high-temperature superconducting materials could be the key to realizing new technological innovations in electrical grids and power storage devices, the development of next-generation supercomputers and ultra-powerful MRI machines.
Why did this research need high fields?
High magnetic fields are needed to suppress superconductivity and allow researchers to access a material’s normal metallic state. Fields approaching 100 tesla enabled measurements of quantum oscillations in YBa2Cu3O6+x very close to the maximum transition temperature of 94 kelvin, giving scientists a better picture of how the electrons interact with each other before they become superconducting.
However, YBCO and many other iron-based superconductors remain superconducting near optimum doping well above 100 T demonstrating the need for even HIGHER fields – 120 tesla or even 225 tesla – to find the nature of the normal state under the material’s superconducting dome.
Where was this work published?
B.J. Ramshaw, S.E. Sebastian, R.D. McDonald, James Day, B.S. Tan, Z. Zhu, J.B. Betts, Ruixing Liang, D.A. Bonn, W.N. Hardy, N. Harrison, “Quasiparticle mass enhancement approaching optimal doping in a high-Tc superconductor.” Science 348:6232 (317-320). 2015
Science 17 Apr 2015:
Vol. 348, Issue 6232, pp. 317-320