Fig. 2: 121/123Sb-NQR spectra and illustration of possible CDW patterns.
a The NQR spectra of 121/123Sb at 101.5 K (above TCDW) and 5.1 K (below TCDW). There are five pairs of resonance peaks in the spectrum above TCDW, marked by five pairs of arrows. Each pair of resonance peaks comes from two types of Sb sites in the crystal structure, namely, Sb1 and Sb2. b Close-up of the spectrum between 71MHz and 79MHz, corresponding to ±1/2 ↔ ±3/2 transitions of 121Sb. Below the CDW phase transition, one resonance peak from Sb2 splits into two peaks marked as Sb2-a and Sb2-b, and the peak from Sb1 shifts to high frequency. c, d show the star-of-David and Tri-hexagonal patterns, respectively. The black dashed open circles represent the V site in the pristine crystal structure. The dark yellow and shallow yellow solid circles represent two types of V sites. The olive and shallow olive solid circles represent two types of Sb1 sites. The blue and shallow blue solid circles represent two types of Sb2 sites. e, f show the local structure around the Sb2 site in star-of-David and Tri-hexagonal patterns, respectively. The black arrows indicate the lattice distortion direction.
