### Session P16: Heavy Fermions- Mostly URu2Si2

8:00 AM–11:00 AM, Wednesday, February 29, 2012
Room: 251

Chair: Jason Jeffries, Lawrence Livermore National Laboratory

Abstract ID: BAPS.2012.MAR.P16.4

### Abstract: P16.00004 : Hidden Order Transition in URu$_2$Si$_2$: Evidence for the Emergence of a Coherent Anderson Lattice from Scanning Tunneling Spectroscopy

8:36 AM–8:48 AM

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#### Authors:

Jeremy Figgins
(University of Illinois at Chicago)

Ting Yuan
(University of Illinois at Chicago)

Dirk Morr
(University of Illinois at Chicago)

The heavy-fermion compound URu$_2$Si$_2$ exhibits an onset of Kondo screening around T $\approx$ 55K and undergoes a second order phase transition at T$_0$ = 17.5K into a state with a still unknown hidden order parameter. Recent scanning tunneling spectroscopy experiments have provided insight into the temperature evolution of the electronic structure. Above the hidden order transition, the differential conductance, dI/dV, exhibits a characteristic Fano lineshape. In contrast, below T$_0$, a soft gap opens up in dI/dV and a quasi-particle interference (QPI) analysis reveals a band structure similar to that expected in a screened Kondo lattice. We demonstrate that the experimental dI/dV and QPI results below T$_0$ are consistent with the formation of a coherent Anderson lattice (CAL). In particular, dI/dV exhibits characteristic signatures of the Anderson lattice band structure, such as an asymmetric gap and a peak inside the gap which arises from the van Hove singularity of the heavy f-electron band. We identify several branches of the QPI pattern arising from intra- and interband scattering. Finally, the temperature evolution of dI/dV suggests that the formation of the CAL below the HOT is primarily driven by a strong increase of the lifetime of the heavy quasi-particles.

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2012.MAR.P16.4