Per Delsing | Chalmers University of Technology (original) (raw)

Papers by Per Delsing

Nanoscale Science and Technology, 1998

The charging energy is important for a mesoscopic body with small capacitance to the environment.... more The charging energy is important for a mesoscopic body with small capacitance to the environment. Connecting the small island via low capacitance, high resistance tunnel junctions, the current through the resulting structure will depend upon the charge of the island -charge that can be applied via a gate electrode. For a normal metal island, the current varies periodically with the charge, the periodicity is the electron charge e. If the island is superconducting, the period, e or 2e, depends upon whether the superconducting energy gap is less than or larger than the charging energy. This parity effect can be used to study possible nodes in the gap function of a high-T c superconductor.

Physica B: Condensed Matter, 2000

We have measured the Hall resistance in two-dimensional arrays of ultrasmall aluminium Josephson ... more We have measured the Hall resistance in two-dimensional arrays of ultrasmall aluminium Josephson junctions. We found that the Hall resistance was periodical with respect to an external magnetic "eld applied perpendicular to the plane of the array. We also found that the Hall resistance was a!ected by an applied voltage to a nearby gate electrode, but not by a gate plane sitting underneath the array.

Photons are fundamental excitations of the electromagnetic field and can be captured in cavities.... more Photons are fundamental excitations of the electromagnetic field and can be captured in cavities. For a given cavity with a certain size, the fundamental mode has a fixed frequency f which gives the photons a specific "colour". The cavity also has a typical lifetime tau, which results in a finite linewidth delta f}. If the size of the cavity is

Physical Review Letters, 2007

We measure longitudinal dressed states of a superconducting qubit, the single Cooper-pair box, an... more We measure longitudinal dressed states of a superconducting qubit, the single Cooper-pair box, and an intense microwave field. The dressed states represent the hybridization of the qubit and photon degrees of freedom and appear as avoided level crossings in the combined energy diagram. By embedding the circuit in an rf oscillator, we directly probe the dressed states. We measure their

Physical review. B, Condensed matter, 1996

We have measured the temperature dependence and magnetic field dependence of the zero-bias resist... more We have measured the temperature dependence and magnetic field dependence of the zero-bias resistance (R 0 ) as well as the current-voltage (I-V) characteristics for several two-dimensional arrays of small aluminum Josephson junctions. R 0 (T) decreases with decreasing temperature, which can be described in terms of two types of vortex motion: flux, flow, and vortex tunneling. At temperatures higher than the Kosterlitz-Thouless transition temperature (TϾT c ) or at a bias current greater than the current corresponding to the onset of the nonlinear I-V characteristics (IϾI d ), the effective damping resistance which characterizes flux-flow motion is found to be approximately equal to the junction normal-state resistance R N . At low temperatures and at small bias current, R 0 is temperature independent and remains finite down to our minimum attainable temperature. This finite resistance is found to be dependent on the array size as well as the junction parameters.

Physical review. B, Condensed matter, 1995

We have studied the superconductor-insulator (Sl) phase transition for two-dimensional (2D) array... more We have studied the superconductor-insulator (Sl) phase transition for two-dimensional (2D) arrays of small Josephson junctions in a weak magnetic field. The data were analyzed within the context of the theory of the magnetic-field-tuned SI transition in 20 superconductors. We show resistance scaling curves over several orders of magnitude for the 20 arrays. The critical exponent zz is determined to be 1.05, in good agreement with the theory. Moreover, the transverse (Hall) resistance at the critical field is found to be very small in comparison to the longitudinal resistance.

Physical review. B, Condensed matter, 1994

We have measured the current-voltage (IV) characteristics of several two-dimensional arrays of sm... more We have measured the current-voltage (IV) characteristics of several two-dimensional arrays of small Josephson junctions as a function of temperature, T and magnetic field B. The junctions have relatively large charging energies EC~=1 K, and normal-state resistances RN in the range of 4-150 kOmega. From the IV characteristics we can deduce the zero-bias resistance R0 and the threshold voltage Vt

Physical Review Letters, 2003

We demonstrate that a continuously measured microelectronic circuit, the Cooper-pair box measured... more We demonstrate that a continuously measured microelectronic circuit, the Cooper-pair box measured by a radio-frequency single-electron transistor, approximates a quantum two-level system. We extract the Hamiltonian of the circuit through resonant spectroscopy and measure the excited-state lifetime. The lifetime is more than 105 times longer than the inverse transition frequency of the two-level system, even though the measurement is active.