Photoemission and band-calculation studies of the charge-density wave inCuV2S4

Abstract

We have studied the electronic structure and its changes across the charge-density-wave ͑CDW͒ transition in spinel-type CuV 2 S 4 by photoemission spectroscopy and first-principles band-structure calculations. The photoemission spectra show pseudogap-like behavior and the gap size is estimated to be ϳ90 meV. The large energy scale of the pseudogap compared to the transition temperature and its anomalous temperature dependence implies that the involved interaction is in the strong-coupling regime. The calculated electronic susceptibility (q) shows a small peak at qӍ 11 40 ͓110͔, which is consistent with the observed wave vector q Ӎ 1 4 ͓110͔ characterizing the CDW. This result suggests that Fermi surface nesting is at least partly responsible for the CDW formation.

Correlation between structural and magnetic properties of half‐metallic spinel CuV2S4 due to the order–disorder transition of 3d2(t2g) orbitals of V3+ ions

“…12 from that reported in [1,3,4,6]. The latter data had a sharp decrease at 90 K. The sin- gle crystal and the fine powders used in the present investigations were grown by Nagata's group, who already reported the important magnetic, electric, and thermal properties of CuV 2 S 4 [7,8,10,11,15,16]. At the moment, it is not easy for us to explain the origin of the difference, though we think that the results depend on the type of specimen used -one single crystal, single crystals, polycrystalline fine powders, and polycrystals -in addition to the instrumental condition of the measurements, because the susceptibility depends on correlation between the crystallographic orientation of the specimen used and the direction and strength of the applied magnetic field.…”

“…The crystals were synthesized from the powders in a quartz ampoule by TeCl 4 vapor transport at a growth temperature of 830 °C to 720 °C in a two-zone furnace [16]. The size of the single crystal used, but not twinned, had a rectangular shape of about 1.8 × 2.8 × 3.7 mm…”

“…After the CDW interpretations of the structural, electric, and magnetic anomalies [1], many investigations were carried out of the structural, magnetic, and electric properties of CuV 2 S 4 in the low-temperature region by means of X-ray diffraction [2][3][4][5], magnetic susceptibility [2,3,[5][6][7], electrical resistivity [2,5,[7][8][9][10], and NMR [4][5][6][11][12][13][14], in addition to the electronic density of states (DOS) [15][16][17]. Lu et al [15] argued using X-ray photoemission and X-ray spectroscopy that Cu ions are in the mono-valent state in Structural and magnetic properties of the spinel CuV 2 S 4 have been studied by means of X-ray diffraction using synchrotron radiation and measurements of magnetic susceptibility.…”

Coexistence of charge-density wave and ferromagnetism in Ni2MnGa

“…Photoemission spectroscopy is a standard tool to identify the CDW state. 30,31 However, in a previously published photoemission study on Ni 2 MnGa, the existence of CDW was not established, although a temperature dependent variation of the spectral shape near E F in the pre-martensite phase was observed, it was related to the density of states (DOS) in the martensite phase.…”

“…The spectral weight transfer from below E F to higher BE was predicted by theory of CDW 3 that considers the electron-phonon coupling. Furthermore, from the photoemission studies on other CDW systems, 30,31,50 the spectral weight transfer has been reported to occur over an energy range much larger than the pseudogap. This is also observed here: the spectral weight transfer occurs over the energy range of 0.25 to 0.85 eV (Fig.…”