Thinner Means Stronger: How Ultrathin Films Beat Magnetic Fields ⚡ экспресс
The Pauli limiting field defines the maximum magnetic field at which superconductivity is possible, and in the weak coupling case it equals the condensation energy balanced by the magnetization energy, which depends on the carriers' g-factor. In the layered superconductor PdTe2, quantum confinement modifies the effective g-factor, leading to a thickness-dependent Pauli limit. The in-plane upper critical field (Hc2||) was experimentally measured for intermediate thicknesses down to 20 mK: as thickness decreased from 50 to 19 nm, Hc2|| increased by more than an order of magnitude. Modeling of the temperature and thickness dependences shows that both orbital and spin Zeeman mechanisms contribute. The orbital contribution is expected, but the observed influence of the Zeeman interaction on superconductivity in thin films is novel. The results aid the search for superconductors with mixed and odd-parity pairing, where the enhancement of Hc2|| may indicate unconventional symmetries.
Superconductors are materials that transmit current without loss. In the 1950s, John Bardeen and his colleagues explained that electrons in them pair up, like dance partners. However, Wolfgang Pauli showed that a strong enough magnetic field, like a whirlwind, would tear the pair apart — this is the Pauli limit. But in layered PdTe₂, it's different. When rolled into a film just 19 nanometers thick, the electron pairs find themselves in a cramped room: there's no room to move, the bond strengthens, and you need a hurricane to pull them apart. In the experiment, such a film withstood a field 10 times stronger than a thicker one.
This discovery draws a thread from nanometer-thin films to galactic beacons, touching on the laws of the Standard Model and the concept of entropy in quantum systems.
🎯 A 19-nm-thick PdTe₂ film is five times thinner than the shell of the flu virus. Individual layers of this material can be peeled off with adhesive tape, paving the way for flexible superconducting electronics.