The energy spectrum of a spin-1/2 ladder with mixed interactions

Cheranovskii V., Ezerskaya E., Ozkan I.

JOURNAL OF PHYSICS-CONDENSED MATTER, cilt.13, sa.20, ss.4525-4534, 2001 (SCI-Expanded) identifier identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 13 Sayı: 20
  • Basım Tarihi: 2001
  • Doi Numarası: 10.1088/0953-8984/13/20/313
  • Dergi Adı: JOURNAL OF PHYSICS-CONDENSED MATTER
  • Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Sayfa Sayıları: ss.4525-4534
  • Orta Doğu Teknik Üniversitesi Adresli: Evet

Özet

We studied the energy spectrum of two coupled XY spin-1/2 chains with different exchange integrals and inter-chain interaction of Ising type. The thorough analytical treatment of two-magnon states was given for finite and infinite lattice strips. To study the case of macroscopic number of inverted spins we used the corresponding density matrix renormalization group (DMRG) simulation. We also derived the self-consistent Bardeen-Cooper-Schrieffer (BCS) estimates for the lowest energies of the system. The comparison of the BCS and the DMRG estimates has shown incorrect behaviour of the BCS approximation for energy as a function of the intra-chain exchange integrals. To use the analytical results for two-magnon bound states we proposed a simple approximate formula for the lowest n-magnon energies of an infinite ladder with a more correct dependence on model parameters.