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首页> 外文期刊>Physical review >Weak first-order quantum phase transition in the spin-tetrahedron system Cu_2Te_2O_5Br_2 without lattice contributions
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Weak first-order quantum phase transition in the spin-tetrahedron system Cu_2Te_2O_5Br_2 without lattice contributions

机译：自旋四面体系统Cu_2Te_2O_5Br_2中无晶格贡献的弱一阶量子相变

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摘要

Under pressure the spin tetrahedron system Cu_2Te_2O_5Br_2 shows a softening of the collective magnetic mode whereas the energy of local spin-exchange processes increases. This apparent contradiction is due to the system's proximity to a quantum critical point induced by competing interactions that effectively decouple the tetrahedra. The high-pressure state is therefore nonmagnetic and dominated by valence bond excitations. Anomalies in the frequency and the intensity of magnetic Raman scattering are evidence for a weakly discontinuous evolution of the quantum critical state. In contrast, structural parameters as well as optical phonon modes evolve continuously with pressure without any sign for discontinuous criticality. No new low-energy excitations are observed. In contrast, the expected fingerprints of the spin-liquid phase are broadened due to Dzyaloshinskii-Moriya interactions.
机译：在压力下，自旋四面体系统Cu_2Te_2O_5Br_2表现出集体磁模的软化，而局部自旋交换过程的能量增加。这种明显的矛盾是由于系统与竞争性相互作用所诱导的量子临界点接近，从而有效地使四面体解耦。因此，高压状态是非磁性的，并以价键激发为主。拉曼散射的频率和强度的异常是量子临界态弱不连续演化的证据。相比之下，结构参数以及光学声子模式会随着压力不断变化，而没有任何不连续临界的迹象。没有观察到新的低能激发。相反，由于Dzyaloshinskii-Moriya相互作用，自旋液相的预期指纹变宽了。

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  • 来源
    《Physical review》 |2011年第13期|p.134404.1-134404.5|共5页
  • 作者

    X. Wang; K. Syassen; M. Johnsson; R. Moessner; K.-Y. Choi; P. Lemmens;

  • 作者单位

    Max-Planck-Institutefur Festkorperforschung, D-70569 Stuttgart, Germany;

    Max-Planck-Institutefur Festkorperforschung, D-70569 Stuttgart, Germany;

    Department of Inorganic Chemistry, Stockholm University, S-10691 Stockholm, Sweden;

    Max-Planck-Institute for the Physics of Complex Systems, Nothnitzer Strasse 38, D-01187 Dresden, Germany;

    Department ofPhysics, Chung-Ang University, 221 Huksuk-Dong, Dongjak-Gu, Seoul 156-756, Republic of Korea;

    Institute for Condensed Matter Physics, TU Braunschweig, D-38106 Braunschweig, Germany;

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  • 正文语种 eng
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  • 关键词

    infrared and raman spectra; spin crossover;

    机译：红外和拉曼光谱;自旋交叉;

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