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Calendar of Physics Talks Vienna
| Fermi liquid vs. non-Fermi-liquid behavior in organic conductors: Tuning correlations in low-dimensional electron systems |
| Speaker: | Prof. Martin Dressel (Universität Stuttgart) |
| Abstract: | While the electronic properties of cuprates can be modified by
electron or hole doping, organic conductors provide the opportunity
to tune the strength of electronic correlations more directly.
Varying the bandwidth by (physical or chemical) pressure, the
$\kappa$-phase BEDT-TTF compounds cross over from a Fermi liquid to
a Mott insulator by increasing effective correlations. We
systematically investigate the electronic transport properties in
organic conductors by dc resistivity and optical measurements in
order to extract the temperature and frequency-dependent scattering
rate $1/\tau = A(k_BT)^2 + B(\hbar\omega)^2$. We find corresponding
temperature and frequency ranges in which the parabolic behaviors
are observed. For the first time, we can quantitatively relate the
two prefactors ($A/B=56$) and their enhancement as correlations
increase upon approaching the Mott transition. Conceptually
low-dimensional organic conductors are also good candidates for
quantum criticality because often an ordered state is located next
to a metallic state when the system is tuned by pressure.
Interestingly both are found, order in the spin as well as in the
charge sector. Fermi-liquid behavior observed in the metallic state
seems to be limited to certain regions of the phase diagram with
non-Fermi-liquid properties evolving as the ordered phase is
approached. It is not clear whether these deviations from Fermi
liquid behavior are actually a signature of quantum criticality.
[1] M. Dressel, {\it Quantum criticality in organic conductors?
Fermi-liquid versus non-Fermi-liquid behavior}, J. Phys.: Condens.
Matter {\bf 23}, 293201 (2011). [2] S. Yasin, M. Dumm, B. Salameh,
P. Batail, C. M{\'e}zi{\'e}re and M. Dressel, {\it Transport studies
at the Mott transition of the two-dimensional organic metal}
$\kappa$-(BEDT-TTF)$_2$Cu[N(CN)$_2$]Br$_x$Cl$_{1-x}$, Eur. Phys. J.
B {\bf 79}, 383 (2011). [3] M. Dumm, D. Faltermeier, N. Drichko and
M. Dressel, {\it Bandwidth-controlled Mott transition in}
$\kappa$-(BEDT-TTF)$_2$Cu[N(CN)$_2$]Br$_x$Cl$_{1-x}$: {\it Optical
studies of correlated carriers}, Phys. Rev. B {\bf 79}, 195106
(2009) [4] J. Merino, M. Dumm, N. Drichko, M. Dressel and R. H.
McKenzie, {\it Quasiparticles at the verge of localization near the
Mott metal-insulator transition in a two-dimensional material},
Phys. Rev. Lett. {\bf 100}, 086404 (2008) |
| Date: | Fri, 21.09.2012 |
| Time: | 11:00 |
| Duration: | 45 min |
| Location: | Freihaus Seminarraum 138B, Turm C, 7. OG (rote Leitfarbe) |
| Contact: | Andrei Pimenov |
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