We have been developing an original transport measurement system to investigate surface physics under an environment of ultrahigh vacuum (UHV), very low temperatures (VLT), and high magnetic fields. The system consists of the following two instruments.

1) UHV transport instrument

This instrument allows us to carry out all experiments from sample preparation to surface characterization at the atomic level, electrode fabrications, and transport measurements without breaking UHV (~1×10^-10 mbar). The sample surfaces can be characterized with low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM). Transport measurements can be conducted from room temperature down to low temperatures as low as 1.8 K using helium-flow type variable temperature cryostat (Helitran, ARS).

2) High-magnetic field UHV-VLT transport/STM instrument

This instrument allows us to carry out transport and STM measurements under an environment of UHV, very low temperatures (400 mK), and high magnetic fields (9 T). After prepared in the UHV transport instrument (see above), samples can be loaded into a UHV-compatible cryostat (Cryogentic) via an exchange chamber. The samples can be transferred between the two instruments using a UHV Suitcase (Ferrovac), which protects them from contamination. For STM measurements, it is also possible to prepare samples independently. The sample heads are made of separable capsule modules, which allows us to switch transport and STM modes by exchanging the corresponding capsules.

We are also conducting researches using other instruments such as

• UHV-LT scanning tunneling microscope
• Cryogen-free refrigerator with a superconducting magnet
• Laser-based two-photon angle-resolved photoemission spectrometer.