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Title: Quasi-two-dimensional Bose-Einstein condensation of spin triplets in the dimerized quantum magnet Ba2CuSi2O6Cl2

We synthesized single crystals of composition Ba2CuSi2O6Cl2 and investigated their quantum magnetic properties. The crystal structure is closely related to that of the quasi-two-dimensional (2D) dimerized magnet BaCuSi2O6 also known as Han purple. Ba2CuSi2O6Cl2 has a singlet ground state with an excitation gap of Δ/kB = 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 Ba2CuSi2O6Cl2 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:
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
OSTI Identifier:
1343717
Alternate Identifier(s):
OSTI ID: 1325607