Scanning Tunneling Microscopy in TTF-TCNQ :direct proof of phase and amplitude modulated charge density waves

TL;DR

This study uses low-temperature STM to directly observe charge density waves in TTF-TCNQ, confirming phase transitions and domain structures, and providing evidence for temperature-dependent wave vectors predicted decades ago.

Contribution

It provides the first direct STM evidence of phase and amplitude modulated charge density waves in TTF-TCNQ, confirming theoretical predictions about domain structures and temperature-dependent wave vectors.

Findings

Identification of all CDW phase transitions in TTF-TCNQ

First direct evidence of domains with single plane wave modulated structures

Observation of temperature-dependent transverse wave vectors

Abstract

Charge density waves (CDW) have been studied at the surface of a cleaved TTF-TCNQ single crystal using a low temperature scanning tunneling microscope (STM) under ultra high vacuum (UHV) conditions. All CDW phase transitions of TTF-TCNQ have been identified. The measurement of the modulation wave vector along the a direction provides the first evidence for the existence of domains comprising single plane wave modulated structures in the temperature regime where the transverse wave vector of the CDW is temperature dependent, as hinted by the theory more than 20 years ago.