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Title: Quasi-two-dimensional Bose-Einstein condensation of spin triplets in the dimerized quantum magnet Ba 2 CuSi 2 O 6 Cl 2

We synthesized single crystals of composition Ba 2CuSi 2O 6Cl 2 and investigated their quantum magnetic properties. The crystal structure is closely related to that of the quasi-two-dimensional (2D) dimerized magnet BaCuSi 2O 6 also known as Han purple. Ba 2CuSi 2O 6Cl 2 has a singlet ground state with an excitation gap of Δ/k B = 20.8 K. The magnetization curves for two different field directions almost perfectly coincide when normalized by the g factor except for a small jump anomaly for a magnetic field perpendicular to the c axis. The magnetization curve with a nonlinear slope above the critical field is in excellent agreement with exact-diagonalization calculations based on a 2D coupled spin-dimer model. Individual exchange constants are also evaluated using density functional theory (DFT). The DFT results demonstrate a 2D exchange network and weak frustration between interdimer exchange interactions, supported by weak spin-lattice coupling implied from our magnetostriction data. Lastly, the magnetic-field-induced spin ordering in Ba 2CuSi 2O 6Cl 2 is described as the quasi-2D Bose-Einstein condensation of triplets.
Authors:
 [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [2] ;  [2] ;  [3] ;  [4] ; ORCiD logo [5] ;  [6] ;  [7]
  1. Tokyo Institute of Technology, Tokyo (Japan)
  2. Univ. of Tokyo, Chiba (Japan)
  3. IFW Dresden, Dresden (Germany); Technical Univ. Dresden, Dresden (Germany)
  4. Ehime Univ., Ehime (Japan)
  5. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  6. Sorbonne Univ., Univ. Pierre et Marie Curie - Paris 6, Paris (France)
  7. Aix-Marseille Univ., Marseille Cedex 9 (France)
Publication Date:
OSTI Identifier:
1343717
Report Number(s):
LA-UR-16-28415
Journal ID: ISSN 2469-9950; PRBMDO; TRN: US1701625
Grant/Contract Number:
AC52-06NA25396
Type:
Accepted Manuscript
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 94; Journal Issue: 9; Journal ID: ISSN 2469-9950
Publisher:
American Physical Society (APS)
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; High Magnetic Field Science