Scientists / Open questions

Qikun Xue

Surface physics; topological quantum matter; superconductivity

16 questions

Microscopic origin of the quantum-size-effect modulation of the Kondo temperature of MnPc molecules on Pb(111) thin films: density-of-states versus exchange-coupling mechanisms
Microscopic validation of the quantum Griffiths rare-region mechanism in the field-driven superconductor–metal transition of disordered two-dimensional superconductors
Quantitative, orbital-resolved characterization and predictive control of superexchange coupling in cobalt phthalocyanine molecular spin chains
Microscopic scattering mechanisms limiting quasiparticle lifetimes of topological surface states in Sb2Te3 thin films: step-edge bound states, electron-electron interactions in magnetic field, and defect-induced in-gap states
Open issues of the annealing-tuned phase diagram of single-layer FeSe/SrTiO $_3$ : interfacial doping mechanism, the insulating N phase, the two-dimensional character of the 65 K transition, direct superconductivity confirmation, and the overdoped regime
Stable p-type ZnO, the Mg-incorporation limit of wurtzite MgZnO, and atomic-scale interfacial nucleation control for all-oxide ZnO-based ultraviolet detectors
Proximity-induced superconductivity on the topological surface states of Bi2Se3/Bi2Sr2CaCu2O8+δ: pairing symmetry, interface control, and the route to Majorana zero modes
Microscopic mechanism and quantitative theory of the weak-antilocalization-to-weak-localization crossover in magnetically doped topological-insulator thin films (Cr-doped Bi2Se3)
Quantitative microscopic theory of superconductivity in one-atomic-layer Pb and In films on Si(111): mode-resolved electron-phonon coupling, phase-dependent $T_{\mathrm{C}}$ , and disorder/fluctuation limits
Majorana bound states in 2M-WS2: confirming the topological nature of the vortex zero mode, determining the local factors controlling its occurrence, and identifying intrinsic impurities
Quantitative material-specific theory of Yu-Shiba-Rusinov states of Mn and Cr adatoms on superconducting Pb(111) thin films
Open superconducting and topological questions in the layered transition metal dichalcogenide 2M-WS $_2$ : origin of its intrinsic $T_c = 8.8$ K, the unassigned ~80 T quantum-oscillation frequency, and whether its topological surface states realize topological superconductivity
Realizing and detecting a single Majorana zero mode in a surface vortex core of the proximity-coupled Bi2Se3/NbSe2 topological-insulator heterostructure: required thickness, Fermi-level, and gating conditions
Hot-spot density and the 'superlens' enhancement mechanism in wrinkled nanoporous Au79Ag21 single-molecule SERS substrates
Unresolved spectroscopic and transport targets in the Landau quantization of the topological surface Dirac cone in Bi2Se3
Microscopic origin of interface-enhanced superconductivity above 100 K in single-layer FeSe on SrTiO3

Back to open problems

Microscopic origin of the quantum-size-effect modulation of the Kondo temperature of MnPc molecules on Pb(111) thin films: density-of-states versus exchange-coupling mechanisms

Microscopic validation of the quantum Griffiths rare-region mechanism in the field-driven superconductor–metal transition of disordered two-dimensional superconductors

Quantitative, orbital-resolved characterization and predictive control of superexchange coupling in cobalt phthalocyanine molecular spin chains

Microscopic scattering mechanisms limiting quasiparticle lifetimes of topological surface states in Sb2Te3 thin films: step-edge bound states, electron-electron interactions in magnetic field, and defect-induced in-gap states

Open issues of the annealing-tuned phase diagram of single-layer FeSe/SrTiO3_33​: interfacial doping mechanism, the insulating N phase, the two-dimensional character of the 65 K transition, direct superconductivity confirmation, and the overdoped regime

Stable p-type ZnO, the Mg-incorporation limit of wurtzite MgZnO, and atomic-scale interfacial nucleation control for all-oxide ZnO-based ultraviolet detectors

Proximity-induced superconductivity on the topological surface states of Bi2Se3/Bi2Sr2CaCu2O8+δ: pairing symmetry, interface control, and the route to Majorana zero modes

Microscopic mechanism and quantitative theory of the weak-antilocalization-to-weak-localization crossover in magnetically doped topological-insulator thin films (Cr-doped Bi2Se3)

Quantitative microscopic theory of superconductivity in one-atomic-layer Pb and In films on Si(111): mode-resolved electron-phonon coupling, phase-dependent TCT_{\mathrm{C}}TC​, and disorder/fluctuation limits

Majorana bound states in 2M-WS2: confirming the topological nature of the vortex zero mode, determining the local factors controlling its occurrence, and identifying intrinsic impurities

Quantitative material-specific theory of Yu-Shiba-Rusinov states of Mn and Cr adatoms on superconducting Pb(111) thin films

Open superconducting and topological questions in the layered transition metal dichalcogenide 2M-WS2_22​: origin of its intrinsic Tc=8.8T_c = 8.8Tc​=8.8 K, the unassigned ~80 T quantum-oscillation frequency, and whether its topological surface states realize topological superconductivity

Realizing and detecting a single Majorana zero mode in a surface vortex core of the proximity-coupled Bi2Se3/NbSe2 topological-insulator heterostructure: required thickness, Fermi-level, and gating conditions

Hot-spot density and the 'superlens' enhancement mechanism in wrinkled nanoporous Au79Ag21 single-molecule SERS substrates

Unresolved spectroscopic and transport targets in the Landau quantization of the topological surface Dirac cone in Bi2Se3

Microscopic origin of interface-enhanced superconductivity above 100 K in single-layer FeSe on SrTiO3

Open issues of the annealing-tuned phase diagram of single-layer FeSe/SrTiO $_3$ : interfacial doping mechanism, the insulating N phase, the two-dimensional character of the 65 K transition, direct superconductivity confirmation, and the overdoped regime

Quantitative microscopic theory of superconductivity in one-atomic-layer Pb and In films on Si(111): mode-resolved electron-phonon coupling, phase-dependent $T_{\mathrm{C}}$ , and disorder/fluctuation limits

Open superconducting and topological questions in the layered transition metal dichalcogenide 2M-WS $_2$ : origin of its intrinsic $T_c = 8.8$ K, the unassigned ~80 T quantum-oscillation frequency, and whether its topological surface states realize topological superconductivity