Long‐Range Non‐Coulombic Electron–Electron Interactions between LaAlO₃/SrTiO₃ Nanowires

Abstract

The LaAlO3/SrTiO3 system exhibits unusual magnetic and superconducting behavior arising from electron–electron interactions whose physical origin is not well understood. Quantum transport techniques, especially those involving mesoscopic geometries, can offer insight into these interactions. Here evidence for long‐range electron–electron interactions in LaAlO3/SrTiO3 nanowires, measured through the phenomenon of frictional drag, is reported, in which current passing through one nanowire induces a voltage across a nearby electrically isolated nanowire. Frictional drag mediated by the Coulomb interaction is predicted to decay exponentially with interwire separation, but with the LaAlO3/SrTiO3 nanowire system it is found to be nearly independent of separation. Frictional drag experiments performed with three parallel wires demonstrate long‐range frictional coupling even in the presence of an electrically grounded central wire. Collectively, these results provide evidence for a new long‐range non‐Coulombic electron–electron interaction unlike anything previously reported for semiconducting systems.

Frictional drag between superconducting LaAlO3/SrTiO3 nanowires

“…When two electrical conductors are placed in close proximity, current driven through one ('drive') conductor may induce a voltage (or current) in the second ('drag') conductor. Frictional drag measurements have mostly been carried out between normal state conductors in coupled 2D semiconductor systems [13][14][15][16][17], graphene systems [18,19], 1D semiconductor systems [20][21][22], 1D complex oxide systems [23], and quantum dot systems [24]. Frictional drag in the superconducting regime has been carried out in normal metal-superconductor systems [25,26] and the phenomenon is explained by the local fluctuating electric field induced by mobile vortices in the superconducting layer [27] or Coulomb coupling between two conductors.…”

Instability of a dilute Fermi liquid in the presence of forward scattering

“…long-range interactions were observed 34 . In ref [35], the model was used to explain superconductivity at vanishing level of doping.…”

Frictional drag between superconducting LaAlO$_3$/SrTiO$_3$ nanowires

“…Frictional drag measurements have mostly been carried out between normal state conductors in coupled 2D semiconductor systems [13][14][15][16][17], graphene systems [18,19], 1D semiconductor systems [20][21][22], 1D complex oxide systems [23], and quantum dot systems [24]. Frictional drag in the superconducting regime has been carried out in normal metal-superconductor systems [25,26] and the phenomenon is explained by the local fluctuating electric field induced by mobile vortices in the superconducting layer [27] or Coulomb coupling between two conductors.…”

“…The nature of R 12 in the superconducting regime is qualitatively different from the high magnetic field regime (where the nanowires are not superconducting). In the high magnetic field regime, the drag resistance R ij is antisymmetric [23] with respect to the sourcing current, while the The nature of coupling between nanowires for R S ij and R A ij is still unknown. But according to devices with d ranging from 40nm to 1.5µm , both R S ij and R A ij persist over large separations and are nearly independent…”

“…The rectification of thermal noise in the drive also explains the strong correlation between R A 12 and R S 12 . R A 12 comes from the rectification of the shot noise in the drive nanowire [23]. Shot noise is a non-equilibrium phenomenon depending on the voltage bias across the drive nanowire [30].…”