Quantum-well states at the surface of the heavy-fermion superconductor URu${}_2$Si${}_2$

Abstract

Electrons can form a two-dimensional electron gas at metal surfaces, where lateral confinement leads to quantum-well states. Such states have been observed for highly itinerant electrons, but it remains an open question whether quantum-well states can be formed from strongly correlated electrons. Here we study atomically flat terraces on surfaces of the heavy-fermion superconductor URu${}_2$Si${}_2$ using millikelvin scanning tunneling spectroscopy. We observe two-dimensional heavy fermions (2DHF) with an effective mass 17 times the free electron mass that form quantized states separated by a fraction of a meV. Superconductivity at the surface is induced by the bulk into the 2DHF. Our results provide a new route to realize quantum well states in correlated quantum materials.

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• Quantum-Confined Tunable Ferromagnetism on the Surface of a van der Waals Antiferromagnet NaCrTe2
• Quantum-size effect induced Andreev bound states in ultrathin metallic islands proximitized by a superconductor
• Scanning Tunneling Microscopy in high vectorial magnetic fields
• Dimensionality tuning of heavy-fermion states in ultrathin CeSi2 films