scholarly journals Absence of Superconductivity in the Hubbard Dimer Model for κ-(BEDT-TTF)2X

Crystals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 580
Author(s):  
Dipayan Roy ◽  
R. Torsten Clay ◽  
Sumit Mazumdar
Keyword(s):  
Low Temperatures ◽  
Magnetic Order ◽  
Organic Superconductors ◽  
Density Matrix Renormalization Group ◽  
Magnetic Fluctuations ◽  
Zero Temperature ◽  
Dimer Model ◽  
Density Matrix Renormalization ◽  
Superconducting Pairing ◽  
Direct Calculations

In the most studied family of organic superconductors κ-(BEDT-TTF)2X, the BEDT-TTF molecules that make up the conducting planes are coupled as dimers. For some anions X, an antiferromagnetic insulator is found at low temperatures adjacent to superconductivity. With an average of one hole carrier per dimer, the BEDT-TTF band is effectively 12-filled. Numerous theories have suggested that fluctuations of the magnetic order can drive superconducting pairing in these models, even as direct calculations of superconducting pairing in monomer 12-filled band models find no superconductivity. Here, we present accurate zero-temperature Density Matrix Renormalization Group (DMRG) calculations of a dimerized lattice with one hole per dimer. While we do find an antiferromagnetic state in our results, we find no evidence for superconducting pairing. This further demonstrates that magnetic fluctuations in the effective 12-filled band approach do not drive superconductivity in these and related materials.

LOW ENERGY PROPERTIES OF A FRUSTRATED ANTIFERROMAGNETIC SPIN-1/2 LADDER

2000 ◽  
Vol 14 (09) ◽  
pp. 327-335 ◽  
Author(s):  
XIAOQUN WANG
Keyword(s):  
Low Energy ◽  
Group Method ◽  
Density Matrix Renormalization Group ◽  
Zero Temperature ◽  
Renormalization Group Method ◽  
Impurity Effects ◽  
First Order ◽  
Density Matrix Renormalization ◽  
Two Phases ◽  
Antiferromagnetic Spin

Using the density matrix renormalization group method, we determined the phase diagram of a frustrated antiferromagnetic spin-[Formula: see text] ladder at zero temperature. Two spin-gapped phases, the Haldane phase and the singlet phase, are identified. In particular, impurity effects are experimentally detectable for the Haldane phase. A phase transition between the two phases occurs at any nonzero value of frustration coupling J×. On the phase boundary, the spin gap vanishes for sufficiently small J×. Crossing this line of gapless states, the transition is of second order, while it is of first order for larger J×.

scholarly journals Nearly ferromagnetic spin-triplet superconductivity

Science ◽  
2019 ◽  
Vol 365 (6454) ◽  
pp. 684-687 ◽  
Author(s):  
Sheng Ran ◽  
Chris Eckberg ◽  
Qing-Ping Ding ◽  
Yuji Furukawa ◽  
Tristin Metz ◽  
...  
Keyword(s):  
Quantum Information ◽  
Transition Temperature ◽  
Magnetic Order ◽  
Quantum Information Processing ◽  
Upper Critical Field ◽  
Superconducting Phase ◽  
Zero Temperature ◽  
Topological Excitations ◽  
Spin Triplet ◽  
Superconducting Pairing

Spin-triplet superconductors potentially host topological excitations that are of interest for quantum information processing. We report the discovery of spin-triplet superconductivity in UTe2, featuring a transition temperature of 1.6 kelvin and a very large and anisotropic upper critical field exceeding 40 teslas. This superconducting phase stability suggests that UTe2 is related to ferromagnetic superconductors such as UGe2, URhGe, and UCoGe. However, the lack of magnetic order and the observation of quantum critical scaling place UTe2 at the paramagnetic end of this ferromagnetic superconductor series. A large intrinsic zero-temperature reservoir of ungapped fermions indicates a highly unconventional type of superconducting pairing.

Sign in / Sign up

Export Citation Format

Share Document