Regular Article

Electronic structure of the α-(BEDT-TTF)₂I₃ surface by photoelectron spectroscopy

¹ Laboratoire de Physique des Solides, CNRS-Université Paris-Sud UMR 8502, 91405 Orsay Cedex, France
² Departament de Ciència de Materials i Química Física and Institut de Química Teórica i Computacional (IQTCUB), Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain
³ Institut de Ciència de Materials de Barcelona (CSIC), Campus UAB, 08193 Bellaterra, Spain
⁴ Synchrotron SOLEIL, Saint Aubin BP 48, 91192 Gif-sur-Yvette, France
⁵ CNR-IOM Laboratorio TASC, 34149 Trieste, Italy
⁶ International Centre for Theoretical Physics (ICTP), 34151 Trieste, Italy
⁷ MOLTECH-Anjou, CNRS-Université d’Angers UMR 6200, Bâtiment K, 49045 Angers Cedex, France

^a These two authors contributed equally.
^b Present address: Paul Scherrer Institute, WSLA/205, 5232 Villigen PSI, Switzerland.
^c e-mail: miguel.monteverde@gmail.com

Received: 24 September 2018
Received in final form: 15 January 2019
Published online: 3 April 2019

Abstract

We report anomalies observed in photoelectron spectroscopy measurements performed on α-(BEDT-TTF)₂I₃ crystals. In particular, above its metal-insulator transition temperature (T = 135 K), we observe the lack of a sharp Fermi edge in contradiction with the metallic transport properties exhibited by this quasi-bidimensional organic material. We interpret these unusual results as a signature of a one-dimensional electronic behavior confirmed by DFT band structure calculations. Using photoelectron spectroscopy we probe a Luttinger liquid with a large correlation parameter (α > 1) that we interpret to be caused by the chain-like electronic structure of α-(BEDT-TTF)₂I₃ surface doped by iodine defects. These new surface effects are inaccessible by bulk sensitive measurements of electronic transport techniques.