Probing continuous electronic phase transitions with in-situ temperature gradient*

Angle-resolved photoemission spectroscopy (ARPES) is a powerful tool to probe electronic structure in quantum materials. In recent years, noval sample tuning methods, such as strain control and electrostatic gating, advanced rapidly, making ARPES a valuable tool to investigate both quantum and classical critical phenomena. However, uncontrolled outgassing and sample drift during temperature ramping deteriorates sample surface and severely limits the efficiency and reliability of temperature tuning in conventional ARPES measurements. Here, we circumvent this difficulty by creating a real-space temperature gradient on the sample surface with a home-made heating puck. In combination with micro-spot ARPES, we demonstrate at least 10x efficiency and high repeatability in temperature tuning. Our method opens up the possibility for in-situ phase diagram mapping and studies of critical phenomena in correlated systems. It also creates a new arena to study the electronic behavior in steady state phenomena such as the thermal Hall effect.