Joule-Thomson STM/AFM with ARPES (Tesla)

This integrated system is the newest addition to the LAIR fleet (commissioned in 2019) at 61 Brimacombe. Its Joule-Thomson (JT) STM/AFM operates at 1 K with 170 hr long LHe holding time, enabling undisturbed long measurements such as quasiparticle interference up to a week with better resolution. It is also equipped with a dry superconducting split-pair 1D magnet for a vertical magnetic field up to 3 T. A standard STM tip and a Qplus AFM tip can be used in this JT system, making it capable of spin-polarized STM and magnetic force microscopy combined with the magnetic field.

The JT STM/AFM is connected to the ARPES system via a bidirectional transfer chamber, as shown in Figs. 1 and 2. JT STM/AFM provides a range of tools for acquiring local atomic-scale views of the structure and electronic states of materials. ARPES provides a complementary view of the electrons delocalized across the surface but with a high resolution of their electronic structure in momentum space. This integrated JT STM/AFM-ARPES system gives us the advantage of characterizing surface electronic properties in real and k-space on the very same sample. Our ARPES is optimized for quick high-resolution photoemission spectroscopy measurements and equipped with the cooling and heating sample stage, ranging from -130 °C to 830 °C. The main research interests z of Tesla are studying quantum materials such as graphene, high TC superconductors, and topological semimetals. Some representative images taken on these samples are shown in Figs. 3-5.

Fig. 1. Schematics of Tesla JT STM/AFM-ARPES system

Fig. 2. JT STM/AFM-ARPES system located in an ultra-low vibration space in 61 BRIM

Fig.3. Atomic resolution on Au(111) (a) at 0 T, bias = 0.28 V, IT= 1 nA. (b) during ramping of the magnetic field from 2T to 3 T, bias = 0.12 V, IT = 1.5 nA. (c) at 3 T, bias = 0.12 V, IT = 1.5 nA. More details can be found in Amy’s thesis [1].

Fig. 4. (a) Cu-intercalated graphene/SiC, (b) pristine graphene/SiC [1].

Fig. 5. Topographic images of cleaved Ca10(Pt4As8)(Fe2As2)5: (a) Ca clusters on ordered Pt4As8 layer, (b) disordered Ca on Fe2As2 layer.

[1] Amy Qu, Atomic modification of graphene on silicon carbide: adsorption and intercalation,