Charge-density-wave STM observation in eta-Mo4O11 - art. no. 165428

We present scanning tunneling microscopy (STM) measurements of the two-dime nsional eta -Mo4O11 com pound, which exhibits Peierls transitions at 30 and 109 K. Using a homemade UHV low-temperature STM, we observe at 50 K (betwe en the two transitions) the formation of an incommensurate charge-density w ave (CDW) along the b direction. STM images provide an accurate measurement of the wave vector of this CDW, which is the "nesting'' vector characteriz ing the transition at 109 K. The measured value is in perfect agreement wit h previous electron diffraction and x-ray diffuse scattering measurements. Finally, recording simultaneously STM images at positive and negative sampl e bias, we observe the expected pi phase shift of the CDW, due to a full sp atial separation of the occupied and empty electronic states of the CDW.