YBa2Cu3O7和YBa2Cu3O6能隙结构的计算

Calculations and Analysis of Energy Gaps in YBa2Cu3O7 and YBa2Cu3O6

摘要:

用电子密度泛函方法（DFT）,系统计算了高温超导体YBa2Cu3O7单胞的能隙随温度变化（5K～300K）的规律.计算结果表明,其超导能隙值2△（T）在101meV量级;并在超导临界温度点（Tc=93 K）附近,有超导能隙不为零的极小值;当温度超过Tc时,YBa2Cu3O7有赝能隙存在,且赝能隙随温度升高至T^＊=120K时,达到极大值;当温度超过T^＊时,赝能隙又有明显减小趋势.用DFT方法对YBa2Cu3O6单胞的能隙进行了计算,发现其能隙值是10^2 meV量级,表明它具有半导体能级特征,因而是非超导体.

Abstract:

The LUMO-HOMO energy gaps in YBa2Cu3O7 have been calculated with density functional method (DFT) on a cluster model of unit cell in a wide range of temperatures (5 K~300 K). The results show that the superconducting energy gap (2?(T)) is about 80 meV at Tc (93 K), and decreases smoothly as the temperature increasing. It reaches the minimum at Tc and exhibits pseudogap above Tc. The pseudogap value reaches the maximum at T*(120 K) when the temperature increasing. The calculations by the cluster model of YBa2Cu3O6 unit cell show that the energy gap is about 102meV with characteristic gap of semiconductor.