New insights into correlated materials in the time domain—combining far-infrared excitation with x-ray probes at cryogenic temperatures

Abstract

Modern techniques for the investigation of correlated materials in the time domain combine selective excitation in the THz frequency range with selective probing of coupled structural, electronic and magnetic degrees of freedom using x-ray scattering techniques. Cryogenic sample temperatures are commonly required to prevent thermal occupation of the low energy modes and to access relevant material ground states. Here, we present a chamber optimized for high-field THz excitation and (resonant) x-ray diffraction at sample temperatures between 5 and 500 K. Directly connected to the beamline vacuum and featuring both a Beryllium window and an in-vacuum detector, the chamber covers the full (2-12.7) keV energy range of the femtosecond x-ray pulses available at the Bernina endstation of the SwissFEL free electron laser. Successful commissioning experiments made use of the energy tunability to selectively track the dynamics of the structural, magnetic and orbital order of Ca 2 RuO 4 and Tb 2 Ti 2 O 7 at the Ru (2.96 keV) and Tb (7.55 keV) L-edges, respectively. THz field amplitudes up to 1.12 MV cm −1 peak field were demonstrated and used to excite the samples at temperatures as low as 5 K.

Non-equilibrium dynamics of spin-lattice coupling

“…The tr-XRD experiments were performed at the Bernina endstation 32 , 33 of the ARAMIS branch of SwissFEL at the Paul Scherrer Institute (Switzerland). The tr-RSXD experiments were performed at the Furka endstation, which is a new endstation for time-resolved studies in condensed matters at the Athos branch of SwissFEL at Paul Scherrer Institute ( https://www.psi.ch/en/swissfel/furka ).…”

The Swiss Light Source and SwissFEL at the Paul Scherrer Institute

“… Bernina: Hard X-ray endstation for condensed matter physics and material sciences. Selective X-ray probes that are sensitive to electronic, magnetic, or atomic structures allow the investigation of ultrafast phenomena such as ultrafast electronic phase transitions [ 28 ], correlated materials in the time domain [ 29 ], and alike. The endstation also serves as a flexible platform for a variety of experiments ranging from developments for hard X-ray transient gratings [ 30 ] to supercooled states of water [ 31 ].…”