Role of a higher-dimensional interaction in stabilizing charge density waves in quasi-one-dimensional NbSe3 revealed by angle-resolved photoemission spectroscopy

Abstract

Utilizing a high energy resolution micro-focused laser with a photon energy of 6.3 eV we investigate charge density waves (CDWs) in the archetypal quasi-1D material NbSe3 using angle-resolved photoemission spectroscopy (ARPES). Doing so allows an exceptionally detailed view into the electronic structure of this complex multi-band system and reveals unambiguously the presence of CDW gaps at the Fermi level (EF). By employing a tight-binding model of the electronic structure, we reveal that the formation of these gaps results from inter-band coupling between electronic states that density functional theory (DFT) finds reside predominantly on separate 1D chains within the material. Two such localized states are found to couple to an electronic state that extends across multiple 1D chains, highlighting the importance of a higher-dimensional environment in stabilizing the CDW ordering in this material. In addition, by investigating the temperature evolution of intra-chain gaps caused by the CDW periodicities far below EF deviate from the behavior expected for a Peierls-like mechanism driven by Fermi nesting; the upper and lower bands of the re-normalized CDW dispersions maintain a fixed peak-to-peak distance while the gaps are gradually removed at higher temperatures. This points towards the gradual loss of long-range phase coherence as the dominant effect in reducing the CDW order parameter which may correspond to the loss of coherence between the coupled chains. Furthermore, one of the gaps is observed above both the known bulk and surface CDW transition temperatures, implying the persistence of short-range incoherent CDW order. Such considerations point to the relevance of a higher-dimensional environment in stabilizing ordered phases in a range of low-dimensional systems. arXiv:1911.00245v2 [cond-mat.str-el]

Correlated Insulator Collapse due to Quantum Avalanche via In-Gap Ladder States

“…The pseudo-gap regime persists until a full IMT occurs at E = E IMT , when the gap ∆ collapses to zero in a strongly discontinuous transition. Unambiguous observation of a pseudogap in the NbSe 3 system was recently made [39,40], consistent with our model in the small-field limit.…”

Uniaxial strain-induced phase transition in the 2D topological semimetal IrTe2

“…In general, such warped Fermi surface contours are characteristic of a strong anisotropy in the electronic hopping parameters and are routinely observed in low-dimensional materials. A small warping corresponds to a low coupling between chains (1D) or planes (2D) along the relevant real-space direction 34,35 . In the case of the present outof-plane dispersion, the narrowing of the warping in the k z direction corresponds to a reduction of the interlayer hopping in the low-temperature phase.…”

Spatial ordering of the charge density waves in NbSe3

“…This is also in accord with the recently published ARPES measurements. These show that both CDW gaps persist well above their onset temperatures and that gradual loss of long-range phase coherence takes place with rising temperature rather than the reduction of the CDW amplitudes 7 .…”

“…It also exhibits interesting transport properties, in particular sliding of its two charge density waves (CDW) in an external electric field 3 . As a result it was thoroughly studied in the past by a variety of different techniques from X-ray diffraction 1,4,5 , Selected Area Electron Diffraction (SADF) Transmission Electron Microscopy (TEM) 6 , Angle Resolved Photoemission Spectroscopy (ARPES) [7][8][9] as well as Scanning Tunneling Microscopy (STM) [10][11][12][13][14][15] . Each of the CDW modes, with q 1 = (0.0, 0.243, 0.0) and q 2 = (0.5, 0.263, 0.5) with onset temperatures T 1 = 144 K and T 2 = 59 K, were originally suggested 1 to selectively modulate one of the three available types of trigonal-prismatic (TP) columns, which form the monoclinic unit cell of the NbSe 3 basic structure (a 0 = 10.009 Å, b 0 = 3.480 Å, c 0 = 15.629 Å, β 0 = 109.47 • , space group P2 1 /m) 1,12 .…”