Spin Gap at the Phase Transition between Spin Liquid and Long-Range Ordered State in La_<1-x>Sr_xCuO_<2.5>
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Two-leg spin S=1/2 antiferromagnetic (AF) spin ladder compound LaCuO<SUB>2. 5</SUB> resides near the quantum critical point. The spin gap at the quantum phase transition from the spin liquid state to the pseudo AF long-range ordered state at about 120 K was investigated by Raman scattering. As temperature increases from 20 K, a dip appears at about 300cm<SUB>-1</SUB> in the magnetic excitation spectrum and develops toward low energy keeping the upper bound at 320 cm<SUB>-1</SUB> and reaches ω∼0 at about 120 K. The in-gap states decrease with further increase of temperature and the gap opens at about 200 K. The low temperature phase below 120 K is not a simple Neel state.
- The Review of High Pressure Science and Technology
The Review of High Pressure Science and Technology 7, 571-573, 1998
The Japan Society of High Pressure Science and Technology