### Thu. March 9, 12:06 p.m. – 12:18 p.m. PST

### Room 318

FeTe_{1-x}Se_{x} is a family of iron-based superconductors with its critical temperature (Tc) dependent on the composition of Se. A well-known *T _{c}* is 14.5 K for x = 0.45, which exhibits an s-wave superconducting gap associated with topological surfaces states. Exchange interaction between the electrons has been proposed as the mechanism behind the formation of singlet Cooper pairs for the sample of FeTe

_{0.5}Se

_{0.5}. We provide further proof that exchange interaction, and hence the associated

*T*, depends on the applied pressure on FeTe

_{c}_{0.5}Se

_{0.5}. Using DFT calculation for electrons and phonons and the Bardeen-Cooper-Schrieffer (BCS) theory for superconductivity, we found that

*T*and superconducting gap for FeTe

_{c}_{0.5}Se

_{0.5}soars under increasing compression, consistent with the results of experiment. UTe

_{2}is a typical triplet superconductor. We will discuss how DFT calculation of exchange integrals and phonon bands affects its

*T*and superconducting gap.

_{c}### Presented By

- Chih-Kai Yang (National Chengchi University)

## DFT calculations for singlet and triplet superconductivity

Thu. March 9, 12:06 p.m. – 12:18 p.m. PST

Room 318

_{1-x}Se

_{x}is a family of iron-based superconductors with its critical temperature (Tc) dependent on the composition of Se. A well-known

*T*is 14.5 K for x = 0.45, which exhibits an s-wave superconducting gap associated with topological surfaces states. Exchange interaction between the electrons has been proposed as the mechanism behind the formation of singlet Cooper pairs for the sample of FeTe

_{c}_{0.5}Se

_{0.5}. We provide further proof that exchange interaction, and hence the associated

*T*, depends on the applied pressure on FeTe

_{c}_{0.5}Se

_{0.5}. Using DFT calculation for electrons and phonons and the Bardeen-Cooper-Schrieffer (BCS) theory for superconductivity, we found that

*T*and superconducting gap for FeTe

_{c}_{0.5}Se

_{0.5}soars under increasing compression, consistent with the results of experiment. UTe

_{2}is a typical triplet superconductor. We will discuss how DFT calculation of exchange integrals and phonon bands affects its

*T*and superconducting gap.

_{c}### Presented By

- Chih-Kai Yang (National Chengchi University)