Spin-1/2 XXZ chain system Cs2CoCl4 in a transverse magnetic field.
Comparing high-resolution specific heat and thermal expansion measurements to exact finite-size diagonalization, we demonstrate that Cs(2)CoCl(4) for a magnetic field along the crystallographic b axis realizes the spin-1/2 XXZ chain in a transverse field. Exploiting both thermal as well as virtual excitations of higher crystal-field states, we find that the spin chain is in the XY limit with an anisotropy J(z)/J[perpindicular] ≈ 0.12, substantially smaller than previously believed. A spin-flop Ising quantum phase transition occurs at a critical field of μ(0)H(b)(cr) ≈ 2 T before around 3.5 T the description in terms of an effective spin-1/2 chain becomes inapplicable.
II. Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, 50937 Köln, Germany.
O
O
Breunig
M
M
Garst
E
E
Sela
B
B
Buldmann
P
P
Becker
L
L
Bohatý
R
R
Müller
T
T
Lorenz