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jeudi 14 Novembre à 14h, Amphi Boreau, escalier C , 2 étage
Strange metal state near quantum superconductor-metal transition in thin films
Konstantin S. Tikhonov and Mikhail V. Feigel’man
L.D.Landau Institute for Theoretical Physics, Moscow
We develop a theory of quantum T = 0 phase transition between metal and superconducting
(q-SMT) ground states in a two-dimensional metal with frozen-in spatial fluctuations δλ(r) of the
Cooper attraction constant. When strength of fluctuations δλ(r) exceeds some critical magnitude,
usual mean-field-like scenario of the q-SMT breaks down due to spontaneous formation of local
droplets of superconducting phase. The density of these droplets grows exponentially with the
Interaction between the droplet’s order parameters increase of the average attraction constant λ.
is due to proximity effect via normal metal and scales with distance ∝ 1/r^β , with 2 < β ≤ 3. We
account for this interaction by means of a real-space renormalization group (RG). Near the q-SMT
the RG flow is a dual equivalent of the Kosterlitz-Thouless RG. The corresponding line of fixed
points describes a Griffiths phase, reminiscent of a ”strange metal”, frequently
√ observed near SMT. Relevant energy/temperature scale drops exponentially, T ∝ exp(−const/ δ),
upon approach of the q-SMT at δ = 0. In a broad range of low temperatures,
conductivity σ is nearly T -independent and diverges at δ → 0.
