Simplified feedback control system for scanning tunneling microscopy

Martín-Vega, Francisco; Barrena, Víctor; Sánchez-Barquilla, Raquel; Fernández-Lomana, Marta; Llorens, José Benito; Wu, Beilun; Fente, A.; Duplain, David Perconte; Horcas, Ignacio; López, Raquel; Blanco, Javier G.; Higuera, Juan Antonio; Mañas‐Valero, Samuel; Jo, Na Hyun; Schmidt, Juan; Canfield, Paul C.; Rubio‐Bollinger, Gabino; Rodrigo, José A.; Herrera, Edwin; Guillamón, Isabel; Suderow, Hermann

doi:10.1063/5.0064511

Cited by 7 publications

(5 citation statements)

References 49 publications

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“…Details of image-rendering software are provided in refs. 42 , 43 . The scanning tunnelling microscope head features a low-temperature movable sample holder, which is used to cleave the sample at cryogenic temperatures 41 , 44 .…”

Section: Methodsmentioning

confidence: 99%

Quantum-well states at the surface of a heavy-fermion superconductor

Herrera

Guillamón

Barrena

et al. 2023

Nature

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Two-dimensional electronic states at surfaces are often observed in simple wide-band metals such as Cu or Ag (refs. 1–4). Confinement by closed geometries at the nanometre scale, such as surface terraces, leads to quantized energy levels formed from the surface band, in stark contrast to the continuous energy dependence of bulk electron bands2,5–10. Their energy-level separation is typically hundreds of meV (refs. 3,6,11). In a distinct class of materials, strong electronic correlations lead to so-called heavy fermions with a strongly reduced bandwidth and exotic bulk ground states12,13. Quantum-well states in two-dimensional heavy fermions (2DHFs) remain, however, notoriously difficult to observe because of their tiny energy separation. Here we use millikelvin scanning tunnelling microscopy (STM) to study atomically flat terraces on U-terminated surfaces of the heavy-fermion superconductor URu2Si2, which exhibits a mysterious hidden-order (HO) state below 17.5 K (ref. 14). We observe 2DHFs made of 5f electrons with an effective mass 17 times the free electron mass. The 2DHFs form quantized states separated by a fraction of a meV and their level width is set by the interaction with correlated bulk states. Edge states on steps between terraces appear along one of the two in-plane directions, suggesting electronic symmetry breaking at the surface. Our results propose a new route to realize quantum-well states in strongly correlated quantum materials and to explore how these connect to the electronic environment.

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Section: Methodsmentioning

confidence: 99%

Quantum-well states at the surface of a heavy-fermion superconductor

Herrera

Guillamón

Barrena

et al. 2023

Nature

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“…To render images and tunneling conductance measurements, we used software described in Refs. [30,31].…”

Section: Experiments and Methodsmentioning

confidence: 99%

“…To obtain the superconducting density of states N (E ) as a function of temperature, we deconvolute N (E ) from the tunneling conductance σ (V ), following Refs. [30,[41][42][43][44]…”

Section: A Scanning Tunneling Microscopy and Spectroscopymentioning

confidence: 99%

Band structure, superconductivity, and polytypism in AuSn4

Herrera

O’Leary

et al. 2023

Phys. Rev. Materials

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The orthorhombic compound AuSn 4 is compositionally similar to the Dirac node arc semimetal PtSn 4 . AuSn 4 is, contrary to PtSn 4 , superconducting with a critical temperature of T c = 2.35 K. Recent measurements present indications for quasi-two-dimensional superconducting behavior in AuSn 4 . Here we present measurements of the superconducting density of states and the band structure of AuSn 4 through scanning tunneling microscopy and angular resolved photoemission spectroscopy (ARPES). The superconducting gap values in different portions of the Fermi surface are spread around 0 = 0.4 meV, which is close to but somewhat larger than = 1.76k B T c expected from BCS theory. We observe superconducting features in the tunneling conductance at the surface up to temperatures about 20% larger than bulk T c . The band structure calculated with density functional theory follows well the results of ARPES. The crystal structure presents two possible stackings of Sn layers, giving two nearly degenerate polytypes. This makes AuSn 4 a rather unique case with a three-dimensional electronic band structure but properties ressembling those of low-dimensional layered compounds.

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“…To render images and tunneling conductance measurements we used software described in Refs. [36,37].…”

Section: Experiments and Methodsmentioning

confidence: 99%

“…To obtain the superconducting density of states N (E) as a function of temperature, we deconvolute N (E) from the tunneling conductance σ(V ), follow-ing Refs. [36,[54][55][56][57]…”

Section: B Scanning Tunneling Microscopymentioning

confidence: 99%