Longitudinal Spin-Wave Mode Near Quantum Critical Point Due to Uniaxial Anisotropy

Development of multi-frequency ESR system for high-pressure measurements up to 2.5 GPa

“…This paramagnet was originally studied as one of the candidates for exhibiting field-induced magnetic ordering above a critical field where the S z = −1 branch crosses the S z = 0 branch [24]. Recently, the longitudinal mode in the pressure-induced ordered phase, as is seen in the spin-1/2 dimer system TlCuCl 3 under pressure [9], has been predicted to appear theoretically in an S = 1 system with uniaxial anisotropy [25]. Although pressure dependence ESR measurements of this compound were previously performed up to 1.5 GPa [13], an ordered state was not identified.…”

“…The spin Hamiltonian of NiSnCl 6 ·6H 2 O for the field parallel to the [111] direction (zaxis) is described as H = g z µ B S z H z + DS 2 z , where g z , µ B , S z , H z and D are the g-value, the Bohr magneton, the spin quantum number (S z = −1, 0, 1), the external magnetic field and the D-value, respectively. As the D-value is known to be positive [23], this compound is certainly a candidate for a substance exhibiting a longitudinal mode under pressure [25]. From this Hamiltonian, two linear resonance conditions, which intercept the frequency axis with the opposite signs, hν = g z µ B H z ± D, are obtained, where h and ν are the Planck constant and the frequency, respectively.…”

Magnetic-field- and pressure-induced quantum phase transition inCsFeCl3proved via magnetization measurements

“…The Higgs mode is a collective mode of amplitude oscillations of order parameters [2,[21][22][23]. A requirement for observing the Higgs mode is shrinkage of the ordered moment in zero applied field, as realized in the pressure-induced ordered phase.…”

Anticrossing effect between magnon and phonon in Bose-Einstein condensation phase of TlCuCl3

“…We analytically show that the one-magnon excitation at the magnetic Γ point is observed only in the magnon BEC phase. The Raman scattering is a suitable probe to detect the longitudinal spin fluctuations which is parallel to the ordered moment [8,9]. In this work, we show the Raman spectra in TlCuCl 3 under the magnetic field up to 12 T. We will present the anticrossing effect between the magnon and phonon by an interaction between them.…”