We investigate the thickness-dependent electronic properties of ultrathin SrIrO_{3} and discover a transition from a semimetallic to a correlated insulating state below 4 unit cells. Low-temperature magnetoconductance measurements show that spin fluctuations in the semimetallic state are significantly enhanced while approaching the transition point. The electronic properties are further studied by scanning tunneling spectroscopy, showing that 4 unit cell SrIrO_{3} is on the verge of a gap opening. Our density functional theory calculations reproduce the critical thickness of the transition and show that the opening of a gap in ultrathin SrIrO_{3} requires antiferromagnetic order.

The control of atomic vacancies on a chlorine-terminated Cu(100) surface by means of a scanning tunnelling microscope tip makes it possible to construct a rewritable atomic memory of over a kilobyte in size with an information density as high as 502 terabits per square inch. The advent of devices based on single dopants, such as the single-atom transistor1, the single-spin magnetometer2,3 and the single-atom memory4, has motivated the quest for strategies that permit the control of matter with atomic precision. Manipulation of individual atoms by low-temperature scanning tunnelling microscopy5 provides ways to store data in atoms, encoded either into their charge state6,7, magnetization state8,9,10 or lattice position11. A clear challenge now is the controlled integration of these individual functional atoms into extended, scalable atomic circuits. Here, we present a robust digital atomic-scale memory of up to 1 kilobyte (8,000 bits) using an array of individual surface vacancies in a chlorine-terminated Cu(100) surface. The memory can be read and rewritten automatically by means of atomic-scale markers and offers an areal density of 502 terabits per square inch, outperforming state-of-the-art hard disk drives by three orders of magnitude. Furthermore, the chlorine vacancies are found to be stable at temperatures up to 77 K, offering the potential for expanding large-scale atomic assembly towards ambient conditions.

Lortz et al (2006 Phys. Rev. B 73 024512) have utilized specific heat and resistivity measurements as ‘thermal spectroscopies’ to deconvolve the spectrum of the electron–phonon interaction in YB6, assuming a major role of the low frequency phonon mode in mediating superconductivity. Here, we present direct point-contact spectroscopy studies of the superconducting interaction in this system. As a result, the normalized superconducting gap reveals a strong coupling with 2Δ/kBTc = 4 and, moreover, the spectra contain nonlinearities typical of the electron–phonon interaction at energies around 8 meV. The measurements in a magnetic field evidence that the phonon features found in the second derivative of the current–voltage characteristics are due to the energy dependence of the superconducting energy gap as their energy position shrinks equally as the gap is closed. This provides direct proof that the superconducting coupling in the system is due to the low energy Einstein-like phonon mode associated with the yttrium ion vibrations, in perfect agreement with determinations from bulk measurements.

Point contact spectroscopy results are presented on the electron underdoped Ba(Fe0.96Co0.04)2As2single crystals.Two superconducting energy gaps with coupling values 2∆1 ∼ kTc ≈ 2.55 and 2∆2 ∼ kTc ≈ 11 at Tc = 15.5 K have been observed in the point contact spectra.The temperature dependence of the normal state background of the point contact spectra observed between Tc and TN indicates antiferromagnetic origin of the V-shaped minimum at zero bias.

Point Contact Spectroscopy Measurements of Ba(Fe0.96Co0.04)2As2 Single Crystals P. Szabóa,∗, J. Girovský, Z. Pribulová, T. Samuely, S.L. Bud’ko, P.C. Canfield and P. Samuely Centre of Low Temperature Physics, IEP Slovak Academy of Sciences & P.J. Šafárik University Watsonova 47, SK-04353 Košice, Slovakia Ames Laboratory and Iowa State University, Ames, IA 50011, USA Point contact spectroscopy results are presented on the electron underdoped Ba(Fe0.96Co0.04)2As2 single crystals. Two superconducting energy gaps with coupling values 2∆1 ∼ kTc ≈ 2.55 and 2∆2 ∼ kTc ≈ 11 at Tc = 15.5 K have been observed in the point contact spectra. The temperature dependence of the normal state background of the point contact spectra observed between Tc and TN indicates antiferromagnetic origin of the V-shaped minimum at zero bias. PACS numbers: 74.50.+r, 74.70.Ad, 74.62.Dh

Point-contact spectroscopy studies of the superconducting energy gap and the electron-phonon coupling mechanism are performed on the boron rich YB6 and ZrB12 single crystals The obtained values of the superconducting energy gaps suggest the strong coupling with 2 Delta/k(B)T(c) approximate to 4 2 for YB6 and 2 Delta/k(B)T(c) approximate to 4 15 for ZrB12 We have observed the dominant soft phonon modes mediating superconductivity in the both samples at energy approximate to 8 meV for YB6 and approximate to 11 meV in ZrB12, respectively

Point contact spectroscopy results are presented on the electron underdoped Ba(Fe-0 Co-96(0) (04))(2)As-2 single crystals Two superconducting energy gaps with coupling values 2 Delta(1) similar to kT(c) approximate to 2 55 and 2 Delta(2) similar to kT(c) approximate to 11 at T-c = 15 5 K have been observed in the point contact spectra The temperature dependence of the normal state background of the point contact spectra observed between T-c and T-N indicates antiferromagnetic origin of the V-shaped minimum at zero bias

Direct experimental studies via the point-contact spectroscopy of the superconducting energy gap and the strong coupling features of the yttrium hexaboride are presented. The phonon structures in the point contact spectra in the supeconducting and normal state are compared. As a result the low energy Einstein-like phonon mode at ∼ 7.5 meV associated with the yttrium ion vibrations seems to be the main mediator of strongly coupled Cooper pairs in this system.