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Ultrafast optical control of the electronic properties of ZrTe5

The ability to manipulate the electronic transport properties in functional materials by sub-picosecond (10-12 s) light pulses is of paramount importance for some future cutting edge electronic and magnetic devices.
Nowadays, ultrafast optical switches are mostly designed by exploiting the metal-insulator phase transitions in suitable oxides. However,ZrTe5 is emerging as one of the most promising platform for its unique and exotic transport, magnetic and thermoelectric properties. Hence, the full control of these properties on an ultra-short time scale is of pivotal importance for the full integration of this material in the electronic components of the actual advanced technologies.
In particular, ZrTe5 shows a resistivity peak versus temperature (at T* ~160 K) accompanied by a quite unusual switching of the charge carriers nature, i.e. from holes to electrons. Furthermore, as a result of either the presence of three-dimensional Dirac particles or spin polarized two-dimensional Dirac particles, the magneto-resistivity has a positive sign when the magnetic field is applied out-of-plane, and a negative sign for magnetic fields in the plane.
By conventional angle resolved photoemission spectroscopy (ARPES), non-linear ARPES (two-photon photoemission) and time resolve ARPES (TR-ARPES) experiments carried on at the T-ReX laboratory we have been able to disclose the unusual temperature dependent behaviour of the ZrTe5 electronic structure around the Fermi energy.
Furthermore, by unveiling the non-equilibrium behaviour of the ZrTe5 electronic structure we opened the route for manipulating some electronic properties via ultrafast coherent light pulses.
In more details we have detected at the Gpoint a temperature dependent hole-like band whose energy shifts for ~60 meV as the temperature is dropt from 300 K to 125 K. The full behaviour of the ZrTe5 band structure have been disclosed by non-linear ARPES experiments that have shown a transiently populated electron-like state above the Fermi energy having a band velocity comparable to the hole-like state observed below the Fermi energy.
This finding has opened the possibility to interpret these states in terms of linearly dispersing 3D Dirac particles. Additionally, these results are compatible with an energy gap smaller than 50 ± 10 meV, hence comparable with the detected energy shift.
The scenario arising from this comprehensive investigation of both the occupied (VB) and unoccupied (CB) states of ZrTe5 reveals for both these bands a temperature dependent binding energy that remarkably clarifies the origin of the resistivity anomaly at T*∼160 K. Also, the observed charge carriers switching, i.e. from holes to electrons, across T* reasonably explains the sign change of the thermo-power.
Finally, we also proved, by mean of TR-ARPES experiments (Figure 1b), the possibility of controlling the VB and CB binding energy on ultra-short timescales by using coherent ultrafast laser excitations. This result provides an external knob to optically manipulate the ZrTe5 conductivity and to unlock the route for magneto-electric, optical, and thermo-electric transport applications.

Figure 1. ARPES (a) differential spectrum obtained from ZrTe5 at 300 K and 125 K. Tr-ARPES (b) differential spectrum obtained from ZrTe5 after and before the time zero. The band shift is evident with both the heating.  

This research was conducted by the following research team:


Giulia Manzoni1, Andrea Sterzi1, Alberto Crepaldi2, Michele Diego1, Federico Cilento2, Michele Zacchigna3, Philippe Bougnon4, Helmuth Berger4, Arnaud Magrez4, Marco Grioni4, Fulvio Parmigiani1,2,5.


1Università degli Studi di Trieste, Trieste, Italy
2Elettra - Sincrotrone Trieste S.C.p.A., Trieste, Italy
3CNR-IOM Trieste, Trieste, Italy
4EPFL Lausanne, Switzerland
5International faculty, University of Köln, Germany



Contact person:

Fulvio Parmigiani, email: fulvio.parmigiani@elettra.eu
Alberto Crepaldi, email: alberto.crepaldi@epfl.ch

Reference

G. Manzoni, A. Sterzi, A. Crepaldi, M. Diego, F. Cilento, M. Zacchigna, Ph. Bugnon, H. Berger, A. Magrez, M. Grioni, and F. Parmigiani, “Ultrafast Optical Control of the Electronic Properties of ZrTe5”, Phys. Rev. Lett. 115, 207402 (2015), DOI:10.1103/PhysRevLett.115.207402

 

Last Updated on Monday, 08 February 2016 15:53