The low temperature specific heat of YBCO superconductors is investigated. A model is proposed in which the quantum tunneling of the apex oxygen atom is coupled to the quasiparticle excitations of the superconducting state. A double well potential for the O(4) atom is asssumed consistently with the EXAFS spectra indications. The superconducting state is described in the framework of the BCS theory. A path integral approach is used to derive the partition function of the system. Space-time scaling techniques allow one to renormalize the coupling between O(4) tunneling states (TS) and the order parameter as a function of temperature. It is suggested that the TS are responsible for the breaking of a fraction of Cooper pairs in the superconducting state.
Quantum Tunneling of the Apex Oxygen Atom and Low Temperature Specific Heat inYBCO Superconductors
ZOLI, Marco
1992-01-01
Abstract
The low temperature specific heat of YBCO superconductors is investigated. A model is proposed in which the quantum tunneling of the apex oxygen atom is coupled to the quasiparticle excitations of the superconducting state. A double well potential for the O(4) atom is asssumed consistently with the EXAFS spectra indications. The superconducting state is described in the framework of the BCS theory. A path integral approach is used to derive the partition function of the system. Space-time scaling techniques allow one to renormalize the coupling between O(4) tunneling states (TS) and the order parameter as a function of temperature. It is suggested that the TS are responsible for the breaking of a fraction of Cooper pairs in the superconducting state.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
