Moscow Institute of Physics and Technology

Theoretical nanophysics laboratory

Upcoming quantum-nanophysics seminars
Scientific Council of the Landau Institute, Friday, October 20, 2017, Landau Institute, 11:30 am

L. Ioffe. M. Feigel'man

Mikrovolnovye svoistva sverkhprovodnikov vblizi perekhoda v izolyator

Predlozhena osnova teorii kollektivnykh mod v sil'no neuporyadochennykh sverkhprovodnikakh, nakhodyashchikhsya vblizi kvantovogo perekhoda v dielektricheskoe sostoyanie. Pokazano, chto s priblizheniem parametrov sverkhprovodnika k kvantovoi kriticheskoi tochke, v spektre vozbuzhdenii s neizbezhnost'yu voznikaet nenulevaya plotnost' nizkolezhashchikh (s energiyami sushchestvenno nizhe sverkhprovodyashchei shcheli) sostoyanii. Pri eshche bol'shem besporyadke eti podshchelevye sostoyaniya okazyvayutsya delokalizovannymi, chto dolzhno privodit' k zametnoi dissipatsii v mikrovolnovom otklike.

Visiting address:

Laboratory building, room 122
Moscow Institute of Physics and Technology
Dolgoprudny, Russia

contact e-mail address: nanotheory@phystech.edu (head M.V.Feigel'man, deputy head I.V.Zagorodnev)

Research topics
  • Mesoscopic electronic systems
  • Superconducting hybrid structures
  • Quantum phase transitions
  • Spintronics
  • 2DEG and quantum Hall effect
  • Quantum magnetism and topological order
  • Physics of quantum computation
Recent quantum-nanophysics seminars
Scientific Council of the Landau Institute, Friday, October 6, 2017, Landau Institute, 11:30 am

Igor Poboiko and Mikhail Feigel'man

Paraconductivity of pseudogapped superconductors

We calculate Aslamazov-Larkin paraconductity for a model of strongly disordered superconductors (dimensions d=2,3) with a large pseudogap whose magnitude strongly exceeds transition temperature Tc. We show that, within Gaussian approximation over Cooper-pair fluctuations, paraconductivity is just twice larger that the classical AL result at the same ε = (T-Tc)/Tc. Upon decreasing ε, Gaussian approximation is violated due to local fluctuations of pairing fields that become relevant at ε < ε1 « 1. Characteristic scale ε1 is much larger than the width ε2 of the thermodynamical critical region, that is determined via the Ginzburg criterion, ε2 ≈ ε1d. We argue that in the intermediate region ε2 < ε < ε1 paraconductivity follows the same AL power law, albeit with another (yet unknown) numerical prefactor. At further decrease of the temperature, all kinds of fluctuational corrections become strong at ε < ε2; in particular, conductivity occurs to be strongly inhomogenuous in real space.